Journal articles on the topic 'Methionase enzyme'
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Sharma, Bhupender, Sukhdev Singh, and Shamsher S. Kanwar. "L-Methionase: A Therapeutic Enzyme to Treat Malignancies." BioMed Research International 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/506287.
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Cancer is an increasing cause of mortality and morbidity throughout the world.L-methionase has potential application against many types of cancers.L-Methionase is an intracellular enzyme in bacterial species, an extracellular enzyme in fungi, and absent in mammals.L-Methionase producing bacterial strain(s) can be isolated by 5,5′-dithio-bis-(2-nitrobenzoic acid) as a screening dye.L-Methionine plays an important role in tumour cells. These cells become methionine dependent and eventually follow apoptosis due to methionine limitation in cancer cells.L-Methionine also plays an indispensable role in gene activation and inactivation due to hypermethylation and/or hypomethylation. Membrane transporters such as GLUT1 and ion channels like Na2+, Ca2+, K+, and Cl−become overexpressed. Further, the α-subunit of ATP synthase plays a role in cancer cells growth and development by providing them enhanced nutritional requirements. Currently, selenomethionine is also used as a prodrug in cancer therapy along with enzyme methionase that converts prodrug into active toxic chemical(s) that causes death of cancerous cells/tissue. More recently, fusion protein (FP) consisting ofL-methionase linked to annexin-V has been used in cancer therapy. The fusion proteins have advantage that they have specificity only for cancer cells and do not harm the normal cells.
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Adams, Jeremy David, Joachim Justad Røise, David Sam Lee, and Niren Murthy. "The methionase chain reaction: an enzyme-based autocatalytic amplification system for the detection of thiols." Chemical Communications 56, no. 21 (2020): 3175–78. http://dx.doi.org/10.1039/c9cc09136j.
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Lockwood, B. C., and G. H. Coombs. "Purification and characterization of methionine γ-lyase from Trichomonas vaginalis." Biochemical Journal 279, no. 3 (November 1, 1991): 675–82. http://dx.doi.org/10.1042/bj2790675.
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Methionine gamma-lyase (EC 4.4.1.11) was purified to homogeneity from the anaerobic protozoan parasite Trichomonas vaginalis by a series of f.p.l.c. procedures. The enzyme catalyses alpha gamma- and alpha beta-elimination reactions of a number of derivatives of methionine and cysteine. It also catalyses gamma-replacement reactions of the thiomethyl group of methionine, homocysteine and ethionine to yield the corresponding S-substituted homocysteine derivative. The enzyme is pyridoxal 5′-phosphate-dependent, has a native molecular mass of approx. 160 kDa and consists of four apparently identical subunits of molecular mass 43-45 kDa. The absorption spectrum of the enzyme is typical of those obtained for other pyridoxal 5′-phosphate-dependent enzymes, and the holoenzyme can be resolved to the apoenzyme by incubation with hydroxylamine and reconstituted by addition of the cofactor. The enzyme activity is significantly affected by carbonyl and thiol reagents, is competitively inhibited by a number of substrate analogues and is completely inactivated by the suicide inhibitor DL-propargylglycine. The T. vaginalis enzyme is similar, in terms of activity and properties, to the enzymes found in a number of species of bacteria that metabolize methionine under anaerobic conditions. It is suggested that methionine catabolism may be of particular importance to the survival of T. vaginalis under microaerophilic conditions in its host.
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Wat, Chi-Kit, Paul Steffens, and Meinhart H. Zenk. "Partial Purification and Characterization of S-Adenosyl-ʟ-Methionine: Norreticuline N-Methyltransferases from Berberis Cell Suspension Cultures." Zeitschrift für Naturforschung C 41, no. 1-2 (February 1, 1986): 126–34. http://dx.doi.org/10.1515/znc-1986-1-219.
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Abstract Two new N-methyltransferases (NMT-I and NMT-II) were found to occur in Berberis vulgaris cell suspension cultures. One of these enzymes (NMT-I) was partially purified (100-fold) and characterized. This enzyme is specific for tetrahydrobenzylisoquinoline alkaloids and S-adenosyl-ʟ-methionine serves as the methyl donor. The apparent molecular weight of the enzyme is 68,000. The pH optimum of the enzyme is 7.6, the temperature optimum 35 °C. Apparent KM values for (R)-tetrahydropapaverin as substrate were 0.2 mᴍ and for SAM 0.04 mᴍ. The preparation of the same type of enzyme from B. wilsoniae var. subcaulialata was utilized as an efficient enzymatic system for the synthesis of stereochemically pure (R)-as well as (S)-reticuline labelled with tritium or 14C at the N-CH3 group. Enzymes catalyzing this type of reactions are named S-adenosyl-ʟ-methionine: norreticuline N-methyltransferases.
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Swanson, Deborah A., Mei-Lan Liu, Priscilla J. Baker, Lisa Garrett, Michael Stitzel, Jianmin Wu, Michelle Harris, Ruma Banerjee, Barry Shane, and Lawrence C. Brody. "Targeted Disruption of the Methionine Synthase Gene in Mice." Molecular and Cellular Biology 21, no. 4 (February 15, 2001): 1058–65. http://dx.doi.org/10.1128/mcb.21.4.1058-1065.2001.
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ABSTRACT Alterations in homocysteine, methionine, folate, and/or B12 homeostasis have been associated with neural tube defects, cardiovascular disease, and cancer. Methionine synthase, one of only two mammalian enzymes known to require vitamin B12 as a cofactor, lies at the intersection of these metabolic pathways. This enzyme catalyzes the transfer of a methyl group from 5-methyl-tetrahydrofolate to homocysteine, generating tetrahydrofolate and methionine. Human patients with methionine synthase deficiency exhibit homocysteinemia, homocysteinuria, and hypomethioninemia. They suffer from megaloblastic anemia with or without some degree of neural dysfunction and mental retardation. To better study the pathophysiology of methionine synthase deficiency, we utilized gene-targeting technology to inactivate the methionine synthase gene in mice. On average, heterozygous knockout mice from an outbred background have slightly elevated plasma homocysteine and methionine compared to wild-type mice but seem to be otherwise indistinguishable. Homozygous knockout embryos survive through implantation but die soon thereafter. Nutritional supplementation during pregnancy was unable to rescue embryos that were completely deficient in methionine synthase. Whether any human patients with methionine synthase deficiency have a complete absence of enzyme activity is unclear. These results demonstrate the importance of this enzyme for early development in mice and suggest either that methionine synthase-deficient patients have residual methionine synthase activity or that humans have a compensatory mechanism that is absent in mice.
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Berger, Louise C., Judith Wilson, Pamela Wood, and Bradley J. Berger. "Methionine Regeneration and Aspartate Aminotransferase in Parasitic Protozoa." Journal of Bacteriology 183, no. 15 (August 1, 2001): 4421–34. http://dx.doi.org/10.1128/jb.183.15.4421-4434.2001.
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ABSTRACT Aspartate aminotransferases have been cloned and expressed fromCrithidia fasciculata, Trypanosoma brucei brucei, Giardia intestinalis, andPlasmodium falciparum and have been found to play a role in the final step of methionine regeneration from methylthioadenosine. All five enzymes contain sequence motifs consistent with membership in the Ia subfamily of aminotransferases; the crithidial and giardial enzymes and one trypanosomal enzyme were identified as cytoplasmic aspartate aminotransferases, and the second trypanosomal enzyme was identified as a mitochondrial aspartate aminotransferase. The plasmodial enzyme contained unique sequence substitutions and appears to be highly divergent from the existing members of the Ia subfamily. In addition, the P. falciparum enzyme is the first aminotransferase found to lack the invariant residue G197 (P. K. Mehta, T. I. Hale, and P. Christen, Eur. J. Biochem. 214:549–561, 1993), a feature shared by sequences discovered in P. vivax and P. berghei. All five enzymes were able to catalyze aspartate-ketoglutarate, tyrosine-ketoglutarate, and amino acid-ketomethiobutyrate aminotransfer reactions. In the latter, glutamate, phenylalanine, tyrosine, tryptophan, and histidine were all found to be effective amino donors. The crithidial and trypanosomal cytosolic aminotransferases were also able to catalyze alanine-ketoglutarate and glutamine-ketoglutarate aminotransfer reactions and, in common with the giardial aminotransferase, were able to catalyze the leucine-ketomethiobutyrate aminotransfer reaction. In all cases, the kinetic constants were broadly similar, with the exception of that of the plasmodial enzyme, which catalyzed the transamination of ketomethiobutyrate significantly more slowly than aspartate-ketoglutarate aminotransfer. This result obtained with the recombinant P. falciparum aminotransferase parallels the results seen for total ketomethiobutyrate transamination in malarial homogenates; activity in the latter was much lower than that in homogenates from other organisms. Total ketomethiobutyrate transamination in Trichomonas vaginalis and G. intestinalis homogenates was extensive and involved lysine-ketomethiobutyrate enzyme activity in addition to the aspartate aminotransferase activity. The methionine production in these two species could be inhibited by the amino-oxy compounds canaline and carboxymethoxylamine. Canaline was also found to be an uncompetitive inhibitor of the plasmodial aspartate aminotransferase, with aKi of 27 μM.
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ROCH, Anne-Marie, Gerard QUASH, Yvonne MICHAL, Jacqueline CHANTEPIE, Bernard CHANTEGREL, Christian DESHAYES, Alain DOUTHEAU, and Jacqueline MARVEL. "Altered methional homoeostasis is associated with decreased apoptosis in BAF3 bcl2 murine lymphoid cells." Biochemical Journal 313, no. 3 (February 1, 1996): 973–81. http://dx.doi.org/10.1042/bj3130973.
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Methional is a potent inducer of apoptosis in an interleukin 3-dependent murine lymphoid cell line BAF3 b0 when it is added to the culture medium. In these cells transfected with the bcl2 gene, BAF3 bcl2, the apoptotic-inducing activity of methional is dramatically reduced. The addition of disulfiram (an inhibitor of aldehyde dehydrogenase) in order to reduce methional oxidation brought about an increase in apoptosis in BAF3 b0 but not in BAF3 bcl2 cells. In contrast, the addition of quercetin (an inhibitor of aldehyde reductase) in an attempt to diminish methional reduction increased apoptosis in both BAF3 b0 and BAF3 bcl2 cells. The extent of DNA fragmentation in BAF3 bcl2 cells approached that in BAF3 b0 cells in the presence of quercetin and exogenous methional, suggesting a defect in methional biosynthesis in BAF3 bcl2 cells. Direct evidence for this was obtained by measuring labelled methional in cells incubated with the sodium salt of [U-14C]4-methylthio-2-oxobutanoic acid (MTOB), the precursor of methional. The 80% decrease in labelled methional in BAF3 bcl2 compared with BAF3 b0 cells was accompanied by a concomitant rise in the transamination of [14C]MTOB to [14C]methionine in BAF3 bcl2 cells. Inhibition of the transaminase, however, by a synthetic transition-state-type compound, pyridoxal-L-methionine ethyl ester, induced apoptosis in BAF3 b0 but not in BAF3 bcl2 cells, confirming that the defect in BAF3 bcl2 cells was not in the transaminase itself but rather in the oxidative decarboxylation step MTOB →methional. In addition, no evidence was obtained for the synthesis of [14C]malondialdehyde from [14C]methional in BAF3 bcl2 cells. As these cells show no deficiency in their content of reactive oxygen species compared with that of BAF3 b0 cells, they may possess some other defect in the β-hydroxylase enzyme system itself.
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Revtovich, Svetlana, Natalya Anufrieva, Elena Morozova, Vitalia Kulikova, Alexey Nikulin, and Tatyana Demidkina. "Structure of methionine γ-lyase fromClostridium sporogenes." Acta Crystallographica Section F Structural Biology Communications 72, no. 1 (January 1, 2016): 65–71. http://dx.doi.org/10.1107/s2053230x15023869.
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Methionine γ-lyase (MGL) is a pyridoxal 5′-phosphate-dependent enzyme that catalyzes the γ-elimination reaction of L-methionine. The enzyme is a promising target for therapeutic intervention in some anaerobic pathogens and has attracted interest as a potential cancer treatment. The crystal structure of MGL fromClostridium sporogeneshas been determined at 2.37 Å resolution. The fold of the protein is similar to those of homologous enzymes fromCitrobacter freundii,Entamoeba histolytica,Pseudomonas putidaandTrichomonas vaginalis. A comparison of these structures revealed differences in the conformation of two flexible regions of the N- and C-terminal domains involved in the active-site architecture.
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Andersen, Gary L., Gwyn A. Beattie, and Steven E. Lindow. "Molecular Characterization and Sequence of a Methionine Biosynthetic Locus from Pseudomonas syringae." Journal of Bacteriology 180, no. 17 (September 1, 1998): 4497–507. http://dx.doi.org/10.1128/jb.180.17.4497-4507.1998.
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ABSTRACT Two methionine biosynthetic genes in Pseudomonas syringae pv. syringae, metX andmetW, were isolated, sequenced, and evaluated for their roles in methionine biosynthesis and bacterial fitness on leaf surfaces. The metXW locus was isolated on a 1.8-kb DNA fragment that was required for both methionine prototrophy and wild-type epiphytic fitness. Sequence analysis identified two consecutive open reading frames (ORFs), and in vitro transcription-translation experiments provided strong evidence that the ORFs encode proteins with the predicted molecular masses of 39 and 22.5 kDa. The predicted amino acid sequence of MetX (39 kDa) showed homology to several known and putative homoserineO-acetyltransferases. This enzyme is the first enzyme in the methionine biosynthetic pathway of fungi, gram-negative bacteria of the genus Leptospira, and several gram-positive bacterial genera. Both metX andmetW were required for methionine biosynthesis, and transcription from both genes was not repressed by methionine. MetW (22.5 kDa) did not show significant homology to any known protein, including prokaryotic and eukaryotic methionine biosynthetic enzymes. Several classes of methionine auxotrophs, includingmetX and metW mutants, exhibit reduced fitness on leaf surfaces, indicating a requirement for methionine prototrophy in wild-type epiphytic fitness. This requirement is enhanced under environmentally stressful conditions, suggesting a role for methionine prototrophy in bacterial stress tolerance.
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Saunderson, C. Linda, and James Mackinlay. "Changes in body-weight, composition and hepatic enzyme activities in response to dietary methionine, betaine and choline levels in growing chicks." British Journal of Nutrition 63, no. 2 (March 1990): 339–49. http://dx.doi.org/10.1079/bjn19900120.
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The experiments described here were set up (a) to investigate the effect of age and (b) to investigate the effect of giving five diets which varied in methionine and choline or betaine contents on some of the enzymes that metabolize these nutrients in chick liver. Growth and carcass composition of the chicks fed on the different diets were also examined. There was no obvious relationship between age and enzyme activity in young chicks. Only a diet low in methionine (but not one low in choline) showed a significant decrease in growth and a change in carcass composition. The effects of diet on enzyme activity were complex. Choline oxidase (EC 1.1.3.17) activity was affected by the level of choline in the diet, being high when choline was present at high levels, especially when methionine was limiting. 5-Methyl-tetrahydrofolate homocysteine methyltransferase (EC 2.1.1.3) had a high activity in the livers of chicks fed on a conventional diet compared with those given semi-purified diets. Other enzymes showed minor changes in response to the diet. The diet low in methionine showed a lower activity of cystathionine η-synthase (EC 4.2.1.22) and slightly higher activities of methionine adenosyltransferase (EC 2.5.1.6) and betaine–homocysteine methyltransferase (EC 2.1.1.5; compared with other diets), suggesting that this diet encouraged re-methylation of homocysteine at the expense of trans-sulphuration to cystathionine. The findings obtained in these studies form a useful basis for further investigation of the metabolic interrelationships between methionine and related nutrients.
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Dib, Iskandar, Damir Stanzer, and Bernd Nidetzky. "Trigonopsis variabilis d-Amino Acid Oxidase: Control of Protein Quality and Opportunities for Biocatalysis through Production in Escherichia coli." Applied and Environmental Microbiology 73, no. 1 (October 20, 2006): 331–33. http://dx.doi.org/10.1128/aem.01569-06.
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ABSTRACT Trigonopsis variabilis d-amino acid oxidase accounts for 35% of Escherichia coli protein when added d-methionine suppresses the toxic activity of the recombinant product. Permeabilized E. coli cells are reusable and stabilized enzyme preparations. The purified oxidase lacks the microheterogeneity of the natural enzyme. Oriented immobilization of a chimeric oxidase maintains 80% of the original activity in microparticle-bound enzymes.
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Fyfe, Cameron D., Noelia Bernardo-García, Laura Fradale, Stéphane Grimaldi, Alain Guillot, Clémence Brewee, Leonard M. G. Chavas, Pierre Legrand, Alhosna Benjdia, and Olivier Berteau. "Crystallographic snapshots of a B12-dependent radical SAM methyltransferase." Nature 602, no. 7896 (February 2, 2022): 336–42. http://dx.doi.org/10.1038/s41586-021-04355-9.
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AbstractBy catalysing the microbial formation of methane, methyl-coenzyme M reductase has a central role in the global levels of this greenhouse gas1,2. The activity of methyl-coenzyme M reductase is profoundly affected by several unique post-translational modifications3–6, such as a unique C-methylation reaction catalysed by methanogenesis marker protein 10 (Mmp10), a radical S-adenosyl-l-methionine (SAM) enzyme7,8. Here we report the spectroscopic investigation and atomic resolution structure of Mmp10 from Methanosarcina acetivorans, a unique B12 (cobalamin)-dependent radical SAM enzyme9. The structure of Mmp10 reveals a unique enzyme architecture with four metallic centres and critical structural features involved in the control of catalysis. In addition, the structure of the enzyme–substrate complex offers a glimpse into a B12-dependent radical SAM enzyme in a precatalytic state. By combining electron paramagnetic resonance spectroscopy, structural biology and biochemistry, our study illuminates the mechanism by which the emerging superfamily of B12-dependent radical SAM enzymes catalyse chemically challenging alkylation reactions and identifies distinctive active site rearrangements to provide a structural rationale for the dual use of the SAM cofactor for radical and nucleophilic chemistry.
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Morozova, E. A., V. V. Kulikova, D. V. Yashin, N. V. Anufrieva, N. Y. Anisimova, S. V. Revtovich, M. I. Kotlov, Y. F. Belyi, V. S. Pokrovsky, and T. V. Demidkina. "Kinetic Parameters and Cytotoxic Activity of Recombinant Methionine γ-Lyase from Clostridium tetani, Clostridium sporogenes, Porphyromonas gingivalis and Citrobacter freundii." Acta Naturae 5, no. 3 (September 15, 2013): 92–98. http://dx.doi.org/10.32607/20758251-2013-5-3-92-98.
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The steady-state kinetic parameters of pyridoxal 5-phosphate-dependent recombinant methionine -lyase from three pathogenic bacteria, Clostridium tetani, Clostridium sporogenes, and Porphyromonas gingivalis, were determined in - and -elimination reactions. The enzyme from C. sporogenes is characterized by the highest catalytic efficiency in the -elimination reaction of L-methionine. It was demonstrated that the enzyme from these three sources exists as a tetramer. The N-terminal poly-histidine fragment of three recombinant enzymes influences their catalytic activity and facilitates the aggregation of monomers to yield dimeric forms under denaturing conditions. The cytotoxicity of methionine -lyase from C. sporogenes and C. tetani in comparison with Citrobacter freundii was evaluated using K562, PC-3, LnCap, MCF7, SKOV-3, and L5178y tumor cell lines. K562 (IC50=0.4-1.3 U/ml), PC-3 (IC50=0.1-0.4 U/ml), and MCF7 (IC50=0.04-3.2 U/ml) turned out to be the most sensitive cell lines.
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Irmler, Stefan, Sylvie Raboud, Beata Beisert, Doris Rauhut, and Hélène Berthoud. "Cloning and Characterization of Two Lactobacillus casei Genes Encoding a Cystathionine Lyase." Applied and Environmental Microbiology 74, no. 1 (September 11, 2007): 99–106. http://dx.doi.org/10.1128/aem.00745-07.
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ABSTRACT Volatile sulfur compounds are key flavor compounds in several cheese types. To better understand the metabolism of sulfur-containing amino acids, which certainly plays a key role in the release of volatile sulfur compounds, we searched the genome database of Lactobacillus casei ATCC 334 for genes encoding putative homologs of enzymes known to degrade cysteine, cystathionine, and methionine. The search revealed that L. casei possesses two genes that putatively encode a cystathionine β-lyase (CBL; EC 4.4.1.8). The enzyme has been implicated in the degradation of not only cystathionine but also cysteine and methionine. Recombinant CBL proteins catalyzed the degradation of l-cystathionine, O-succinyl-l-homoserine, l-cysteine, l-serine, and l-methionine to form α-keto acid, hydrogen sulfide, or methanethiol. The two enzymes showed notable differences in substrate specificity and pH optimum.
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Ferla, Matteo P., and Wayne M. Patrick. "Bacterial methionine biosynthesis." Microbiology 160, no. 8 (August 1, 2014): 1571–84. http://dx.doi.org/10.1099/mic.0.077826-0.
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Methionine is essential in all organisms, as it is both a proteinogenic amino acid and a component of the cofactor, S-adenosyl methionine. The metabolic pathway for its biosynthesis has been extensively characterized in Escherichia coli; however, it is becoming apparent that most bacterial species do not use the E. coli pathway. Instead, studies on other organisms and genome sequencing data are uncovering significant diversity in the enzymes and metabolic intermediates that are used for methionine biosynthesis. This review summarizes the different biochemical strategies that are employed in the three key steps for methionine biosynthesis from homoserine (i.e. acylation, sulfurylation and methylation). A survey is presented of the presence and absence of the various biosynthetic enzymes in 1593 representative bacterial species, shedding light on the non-canonical nature of the E. coli pathway. This review also highlights ways in which knowledge of methionine biosynthesis can be utilized for biotechnological applications. Finally, gaps in the current understanding of bacterial methionine biosynthesis are noted. For example, the paper discusses the presence of one gene (metC) in a large number of species that appear to lack the gene encoding the enzyme for the preceding step in the pathway (metB), as it is understood in E. coli. Therefore, this review aims to move the focus away from E. coli, to better reflect the true diversity of bacterial pathways for methionine biosynthesis.
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Dias, Benjamin, and Bart Weimer. "Conversion of Methionine to Thiols by Lactococci, Lactobacilli, and Brevibacteria." Applied and Environmental Microbiology 64, no. 9 (September 1, 1998): 3320–26. http://dx.doi.org/10.1128/aem.64.9.3320-3326.1998.
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ABSTRACT Methanethiol has been strongly associated with desirable Cheddar cheese flavor and can be formed from the degradation of methionine (Met) via a number of microbial enzymes. Methionine γ-lyase is thought to play a major role in the catabolism of Met and generation of methanethiol in several species of bacteria. Other enzymes that have been reported to be capable of producing methanethiol from Met in lactic acid bacteria include cystathionine β-lyase and cystathionine γ-lyase. The objective of this study was to determine the production, stability, and activities of the enzymes involved in methanethiol generation in bacteria associated with cheese making. Lactococci and lactobacilli were observed to contain high levels of enzymes that acted primarily on cystathionine. Enzyme activity was dependent on the concentration of sulfur amino acids in the growth medium. Met aminotransferase activity was detected in all of the lactic acid bacteria tested and α-ketoglutarate was used as the amino group acceptor. In Lactococcus lactis subsp. cremorisS2, Met aminotransferase was repressed with increasing concentrations of Met in the growth medium. While no Met aminotransferase activity was detected in Brevibacterium linens BL2, it possessed high levels of l-methionine γ-lyase that was induced by addition of Met to the growth medium. Met demethiolation activity at pH 5.2 with 4% NaCl was not detected in cell extracts but was detected in whole cells. These data suggest that Met degradation in Cheddar cheese will depend on the organism used in production, the amount of enzyme released during aging, and the amount of Met in the matrix.
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Miousse, Isabelle. "4006 Methionine Dependence in Cancer: From Metabolic Phenotype to Therapy." Journal of Clinical and Translational Science 4, s1 (June 2020): 12. http://dx.doi.org/10.1017/cts.2020.81.
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OBJECTIVES/GOALS: Methionine dependence was described 45 years ago as an increased reliance on an exogenous supply of the essential amino acid methionine in most cancer cells compared to normal cells. Methionine depletion, using either synthetic diets or the enzyme methioninase, potentiates the effects of chemotherapy and radiotherapy in tumor-bearing animal models. Two main obstacles prevent methionine dependence from integrating the clinical treatment of cancer. The first is the weight loss associated with methionine depletion therapy, increasing the risk of cachexia in patients. The second is the stubborn absence of a mechanism to explain the inability of cancer cells to adapt to low methionine levels. METHODS/STUDY POPULATION: To address these two obstacles, we are using an immunocompetent murine model of metastatic melanoma to compare the effects of complete methionine deprivation with a moderate, 75-80% methionine restriction similar to the one used to increase lifespan in animal models. In an effort to identify a mechanism of action, we also performed a proteomic screen of two melanoma cell lines divergent for methionine dependence under methionine stress. RESULTS/ANTICIPATED RESULTS: We recently showed that methionine restriction is sufficient to provide gains in treating local and metastatic lesions in vivo, without weight loss. We observed few differences in pathway activation between the two cell lines in response to methionine stress, despite proliferation being cut by half in the methionine dependent cell line. We expect that subcellular translocation events may provide further information on the molecular bases of methionine dependence. DISCUSSION/SIGNIFICANCE OF IMPACT: A moderate restriction in methionine is sufficient to recapitulate the benefits of methionine depletion in cancer, without weight loss. The mechanism behind this effect remains unknown. This work contributes towards the integration of methionine dependence into clinical practice and the discovery of novel drug targets.
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Prado, Tayrone F., Aldi F. S. França, Maria Lúcia G. Meirinhos, Hugo J. M. C. Peron, Reginaldo N. Ferreira, Leonardo G. Oliveira, and Daniel S. Corrêa. "Animal performance and carcass characteristics from confined lambs fed on concentrate feed and additives." Anais da Academia Brasileira de Ciências 87, no. 4 (October 30, 2015): 2255–63. http://dx.doi.org/10.1590/0001-3765201520140415.
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ABSTRACT The number of sheep flocks in Brazil is increasing. It is known that lambs must be slaughtered when young for producing quality meat. The current study evaluated the inclusion of protected methionine, protected lysine, lysophospholipid and amylolytic enzymes in a diet to lambs and their effects on weight gain and quantitative carcass traits at slaughtering. Eighty non-castrated male crossbred Dorper x Santa Inês lambs, 20.57 ± 4.33 kg live weight, were used. The feedlot lasted 64 days and 60 animals were slaughtered. There were no differences for live weight, daily feed intake, feed conversion and average daily weight gain at the first 28 days of feedlot. From the 28th day lysophospholipid treatment presented the highest live weight. Lysophospholipid and amylolytic enzyme presented the best performance in average daily gain, followed by protected methionine, control and protected lysine. Lysophospholipid treatment presented higher daily feed intake rates than protected lysine and protected methionine. Feed conversion was lower for amylolytic enzyme and higher for control. No changing in carcass traits was reported due to additives. Better performance may be achieved with feedlot lambs fed on diets with the addition of amylolytic enzyme and lysophospholipid at the finishing phase.
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Brosnan, John T. "Homocysteine and Cardiovascular Disease: Interactions Between Nutrition, Genetics and Lifestyle." Canadian Journal of Applied Physiology 29, no. 6 (December 1, 2004): 773–80. http://dx.doi.org/10.1139/h04-050.
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Homocysteine is a sulfur-containing amino acid that arises during methionine metabolism. Although its concentration in plasma is only about 10 micromolar, even moderate hyperhomocysteinemia is associated with increased incidence of cardiovascular disease and Alzheimer's disease. Elevations in plasma homocysteine are commonly found as a result of vitamin deficiencies, polymorphisms of enzymes of methionine metabolism, and renal disease. Pyridoxal, folic acid, riboflavin, and Vitamin B12 are all required for methionine metabolism, and deficiences of each of these vitamins result in elevated plasma homocysteine. A polymorphism of methylenetetrahydrofolate reductase (C677T), which is quite common in most populations with a homozygosity rate of 10-15%, is associated with moderate hyperhomocysteinemia, especially in the context of marginal folate intake. Plasma homocysteine is inversely related to plasma creatinine in patients with renal disease. This is due to an impairment in homocysteine removal in renal disease. The role of these factors, and of modifiable life style factors, in affecting methionone metabolism and in determining plasma homocysteine levels is discussed. Key words: methionine, liver metabolism, folic acid, vitamin B12, polymorphisms, neural tube defects, end-stage renal disease, coffee consumption
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Murray, Ben, Svetlana V. Antonyuk, Alberto Marina, Shelly C. Lu, Jose M. Mato, S. Samar Hasnain, and Adriana L. Rojas. "Crystallography captures catalytic steps in human methionine adenosyltransferase enzymes." Proceedings of the National Academy of Sciences 113, no. 8 (February 8, 2016): 2104–9. http://dx.doi.org/10.1073/pnas.1510959113.
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The principal methyl donor of the cell, S-adenosylmethionine (SAMe), is produced by the highly conserved family of methionine adenosyltranferases (MATs) via an ATP-driven process. These enzymes play an important role in the preservation of life, and their dysregulation has been tightly linked to liver and colon cancers. We present crystal structures of human MATα2 containing various bound ligands, providing a “structural movie” of the catalytic steps. High- to atomic-resolution structures reveal the structural elements of the enzyme involved in utilization of the substrates methionine and adenosine and in formation of the product SAMe. MAT enzymes are also able to produce S-adenosylethionine (SAE) from substrate ethionine. Ethionine, an S-ethyl analog of the amino acid methionine, is known to induce steatosis and pancreatitis. We show that SAE occupies the active site in a manner similar to SAMe, confirming that ethionine also uses the same catalytic site to form the product SAE.
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Mordukhova, Elena A., and Jae-Gu Pan. "Evolved Cobalamin-Independent Methionine Synthase (MetE) Improves the Acetate and Thermal Tolerance of Escherichia coli." Applied and Environmental Microbiology 79, no. 24 (October 11, 2013): 7905–15. http://dx.doi.org/10.1128/aem.01952-13.
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ABSTRACTAcetate-mediated growth inhibition ofEscherichia colihas been found to be a consequence of the accumulation of homocysteine, the substrate of the cobalamin-independent methionine synthase (MetE) that catalyzes the final step of methionine biosynthesis. To improve the acetate resistance ofE. coli, we randomly mutated the MetE enzyme and isolated a mutant enzyme, designated MetE-214 (V39A, R46C, T106I, and K713E), that conferred accelerated growth in theE. coliK-12 WE strain in the presence of acetate. Additionally, replacement of cysteine 645, which is a unique site of oxidation in the MetE protein, with alanine improved acetate tolerance, and introduction of the C645A mutation into the MetE-214 mutant enzyme resulted in the highest growth rate in acetate-treatedE. colicells among three mutant MetE proteins.E. coliWE strains harboring acetate-tolerant MetE mutants were less inhibited by homocysteine inl-isoleucine-enriched medium. Furthermore, the acetate-tolerant MetE mutants stimulated the growth of the host strain at elevated temperatures (44 and 45°C). Unexpectedly, the mutant MetE enzymes displayed a reduced melting temperature (Tm) but an enhancedin vivostability. Thus, we demonstrate improvedE. coligrowth in the presence of acetate or at elevated temperatures solely due to mutations in the MetE enzyme. Furthermore, when anE. coliWE strain carrying the MetE mutant was combined with a previously found MetA (homoserineo-succinyltransferase) mutant enzyme, the MetA/MetE strain was found to grow at 45°C, a nonpermissive growth temperature forE. coliin defined medium, with a similar growth rate as if it were supplemented byl-methionine.
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Clare, Constance E., Valerie Pestinger, Wing Yee Kwong, Desmond A. R. Tutt, Juan Xu, Helen M. Byrne, David A. Barrett, Richard D. Emes, and Kevin D. Sinclair. "Interspecific Variation in One-Carbon Metabolism within the Ovarian Follicle, Oocyte, and Preimplantation Embryo: Consequences for Epigenetic Programming of DNA Methylation." International Journal of Molecular Sciences 22, no. 4 (February 12, 2021): 1838. http://dx.doi.org/10.3390/ijms22041838.
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One-carbon (1C) metabolism provides methyl groups for the synthesis and/or methylation of purines and pyrimidines, biogenic amines, proteins, and phospholipids. Our understanding of how 1C pathways operate, however, pertains mostly to the (rat) liver. Here we report that transcripts for all bar two genes (i.e., BHMT, MAT1A) encoding enzymes in the linked methionine-folate cycles are expressed in all cell types within the ovarian follicle, oocyte, and blastocyst in the cow, sheep, and pig; as well as in rat granulosa cells (GCs) and human KGN cells (a granulosa-like tumor cell line). Betaine-homocysteine methyltransferase (BHMT) protein was absent in bovine theca and GCs, as was activity of this enzyme in GCs. Mathematical modeling predicted that absence of this enzyme would lead to more volatile S-adenosylmethionine-mediated transmethylation in response to 1C substrate (e.g., methionine) or cofactor provision. We tested the sensitivity of bovine GCs to reduced methionine (from 50 to 10 µM) and observed a diminished flux of 1C units through the methionine cycle. We then used reduced-representation bisulfite sequencing to demonstrate that this reduction in methionine during bovine embryo culture leads to genome-wide alterations to DNA methylation in >1600 genes, including a cohort of imprinted genes linked to an abnormal fetal-overgrowth phenotype. Bovine ovarian and embryonic cells are acutely sensitive to methionine, but further experimentation is required to determine the significance of interspecific variation in BHMT expression.
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Seneviratne, Charita K., Timao Li, Neelam Khaper, and Pawan K. Singal. "Effects of methionine on endogenous antioxidants in the heart." American Journal of Physiology-Heart and Circulatory Physiology 277, no. 6 (December 1, 1999): H2124—H2128. http://dx.doi.org/10.1152/ajpheart.1999.277.6.h2124.
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The deficiency of methionine, an essential amino acid, is associated with cardiovascular lesions. Because different types of cardiac pathologies are caused by a decrease in antioxidants, we examined the effects of methionine on myocardial antioxidant enzymes in hemodynamically assessed rats that were treated with methionine (10 mg/ml) in drinking water for 12, 24, and 48 h. Glutathione peroxidase (GSHPx) activity was significantly increased to 150.5 ± 12.2 and 191.7 ± 13.7% of the control value at 12 and 24 h, respectively, followed by a decline to 120 ± 24.6% at 48 h. The mRNA levels of GSHPx at these time points were 151.2 ± 12.0, 218.7 ± 35.3, and 173.5 ± 25.2%, respectively. Superoxide dismutase (SOD) activity was 144.3 ± 3.7, 114.3 ± 10.1, and 143.1 ± 11.2% at 12, 24, and 48 h, respectively. Catalase (Cat) activity was 272.4 ± 5.4, 237.8 ± 16.6, and 224.1 ± 17.3% of the control value. The expression of Cat and SOD mRNA was unchanged at 12, 24, and 48 h. The lipid peroxidation was decreased by 24.4 ± 11.2, 54.9 ± 0.1, and 6.4 ± 2.1% at 12, 24, and 48 h, respectively. Methionine had no effect on the ventricular or aortic pressures, heart rate, and myocardial glutathione levels at any of the time points. The study shows that methionine has a significant effect on the myocardial antioxidant enzyme activities, and only changes in GSHPx enzyme activity correlated with the mRNA changes. These antioxidant changes may have a role in the beneficial effects of methionine in pathological rather than physiological conditions.
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Kelley, M., and D. A. Vessey. "Structural comparison between the mitochondrial aralkyl-CoA and arylacetyl-CoA N-acyltransferases." Biochemical Journal 288, no. 1 (November 15, 1992): 315–17. http://dx.doi.org/10.1042/bj2880315.
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The aralkyl and arylacetyl transferases were purified to homogeneity from bovine kidney by a slight modification of a previous procedure. The M(r) of the arylacetyl transferase was estimated to be 33,500 by SDS/PAGE and that of the aralkyl transferase to be 33,750 by a combination of SDS/PAGE and gel-filtration analysis. N-Terminal-sequence analysis indicated a blocked N-terminus for the arylacetyl transferase and gave the following sequence for the aralkyl transferase: M-F-L-L-Q-G-A-Q-M-L-Q-M-L-E-K. Amino acid analysis revealed differences in composition between the two enzymes. Most notable was the fact that the aralkyl transferase had more methionine and leucine. This difference could be partially accounted for by assuming that the methionine-and-leucine-rich N-terminus was missing from the arylacetyl transferase. Chemical cleavage of the two enzymes at methionine residues using CNBr gave rise to several peptides for each enzyme. N-Terminal-sequence analysis of the 8000-M(r) peptide from the arylacetyl transferase gave a sequence with 69% similarity to the 9000-M(r) peptide from the aralkyl transferase. This was taken to indicate a common origin for the two enzymes.
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Bella, Deborah L., Lawrence L. Hirschberger, Yu Hosokawa, and Martha H. Stipanuk. "Mechanisms involved in the regulation of key enzymes of cysteine metabolism in rat liver in vivo." American Journal of Physiology-Endocrinology and Metabolism 276, no. 2 (February 1, 1999): E326—E335. http://dx.doi.org/10.1152/ajpendo.1999.276.2.e326.
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Little is known about mechanisms of regulation of cysteine dioxygenase (CDO), γ-glutamylcysteine synthetase (GCS), and cysteine-sulfinate decarboxylase (CSDC) in response to diet. Enzyme activity and Western and Northern or dot blot analyses were conducted on liver samples from rats fed a basal low-protein diet or diets with graded levels of protein or methionine for 2 wk. Higher levels of CDO activity and CDO protein but not of CDO mRNA were observed in liver of rats fed methionine or protein-supplemented diets, indicating that CDO activity is regulated by changes in enzyme concentration. Lower concentrations of the heavy or catalytic subunit of GCS (GCS-HS) mRNA and protein, as well as a lower activity state of GCS-HS in rats fed methionine- or protein-supplemented diets, indicated that dietary regulation of GCS occurs by both pretranslational and posttranslational mechanisms. Lower CSDC activity, CSDC protein concentration, and CSDC mRNA concentration were found in rats fed the highest level of protein, and regulation appeared to involve changes in mRNA concentration. Regulation of key enzymes of cysteine metabolism in response to diet determines the use of cysteine for synthesis of its essential metabolites.
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LOPEZ-CAMACHO, Cristina, Jesus SALGADO, Juan Luis LEQUERICA, Alejo MADARRO, Esteban BALLESTAR, Luis FRANCO, and Julio POLAINA. "Amino acid substitutions enhancing thermostability of Bacillus polymyxa β-glucosidase A." Biochemical Journal 314, no. 3 (March 15, 1996): 833–38. http://dx.doi.org/10.1042/bj3140833.
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Mutations enhancing the thermostability of β-glucosidase A of Bacillus polymyxa, a family 1 glycosyl hydrolase, have been obtained after hydroxylamine mutagenesis of a plasmid containing the bglA gene, transformation of Escherichia coli with the mutagenized plasmid, and identification of transformant colonies that showed β-glucosidase activity after a thermal treatment that inactivated the wild-type enzyme. Two additive mutations have been characterized that cause replacement of glutamate at position 96 by lysine and of methionine at position 416 by isoleucine respectively. The thermoresistant mutant enzymes showed increased resistance to other denaturing agents, such as pH and urea, while their kinetic parameters did not change. CD spectra indicated that the E96K replacement caused an increase in α-helix content. The observed effect of the M416I mutation is consistent with the lower content of cysteine and methionine found in family 1 enzymes of thermophilic species compared with similar ones from mesophilic organisms.
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Vissers, M. C., and C. C. Winterbourn. "Myeloperoxidase-dependent oxidative inactivation of neutrophil neutral proteinases and microbicidal enzymes." Biochemical Journal 245, no. 1 (July 1, 1987): 277–80. http://dx.doi.org/10.1042/bj2450277.
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The susceptibility of a number of human neutrophil granule enzymes to oxidative inactivation was investigated. Addition of H2O2 to the cell-free medium from stimulated neutrophils resulted in inactivation of all enzymes tested. This was inhibited by azide and methionine, indicating that inactivation was due to myeloperoxidase-derived oxidants. Lysozyme was more than 50% inactivated by one addition of 100 nmol of H2O2/ml, whereas myeloperoxidase, beta-glucuronidase, gelatinase and collagenase were almost completely inactivated by three additions. Cathepsin G was slightly less susceptible, whereas elastase was extremely resistant to oxidative attack. Myeloperoxidase-dependent enzyme inactivation may be a means whereby the neutrophil can terminate the activity of its granule enzymes and control the release of degradative enzymes into the tissues.
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Zhao, Chen, Axel Hartke, Marilena La Sorda, Brunella Posteraro, Jean-Marie Laplace, Yanick Auffray, and Maurizio Sanguinetti. "Role of Methionine Sulfoxide Reductases A and B of Enterococcus faecalis in Oxidative Stress and Virulence." Infection and Immunity 78, no. 9 (June 21, 2010): 3889–97. http://dx.doi.org/10.1128/iai.00165-10.
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ABSTRACT Methionine sulfoxide reductases A and B are antioxidant repair enzymes that reduce the S- and R-diastereomers of methionine sulfoxides back to methionine, respectively. Enterococcus faecalis, an important nosocomial pathogen, has one msrA gene and one msrB gene situated in different parts of the chromosome. Promoters have been mapped and mutants have been constructed in two E. faecalis strains (strains JH2-2 and V583) and characterized. For both backgrounds, the mutants are more sensitive than the wild-type parents to exposure to H2O2, and in combination the mutations seem to be additive. The virulence of the mutants has been analyzed in four different models. Survival of the mutants inside mouse peritoneal macrophages stimulated with recombinant gamma interferon plus lipopolysaccharide but not in naïve phagocytes is significantly affected. The msrA mutant is attenuated in the Galleria mellonella insect model. Deficiency in either Msr enzyme reduced the level of virulence in a systemic and urinary tract infection model. Virulence was reconstituted in the complemented strains. The combined results show that Msr repair enzymes are important for the oxidative stress response, macrophage survival, and persistent infection with E. faecalis.
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Vermeij, Paul, and Michael A. Kertesz. "Pathways of Assimilative Sulfur Metabolism inPseudomonas putida." Journal of Bacteriology 181, no. 18 (September 15, 1999): 5833–37. http://dx.doi.org/10.1128/jb.181.18.5833-5837.1999.
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ABSTRACT Cysteine and methionine biosynthesis was studied inPseudomonas putida S-313 and Pseudomonas aeruginosa PAO1. Both these organisms used direct sulfhydrylation of O-succinylhomoserine for the synthesis of methionine but also contained substantial levels of O-acetylserine sulfhydrylase (cysteine synthase) activity. The enzymes of the transsulfuration pathway (cystathionine γ-synthase and cystathionine β-lyase) were expressed at low levels in both pseudomonads but were strongly upregulated during growth with cysteine as the sole sulfur source. In P. aeruginosa, the reverse transsulfuration pathway between homocysteine and cysteine, with cystathionine as the intermediate, allows P. aeruginosa to grow rapidly with methionine as the sole sulfur source. P. putida S-313 also grew well with methionine as the sulfur source, but no cystathionine γ-lyase, the key enzyme of the reverse transsulfuration pathway, was found in this species. In the absence of the reverse transsulfuration pathway, P. putida desulfurized methionine by the conversion of methionine to methanethiol, catalyzed by methionine γ-lyase, which was upregulated under these conditions. A transposon mutant of P. putida that was defective in the alkanesulfonatase locus (ssuD) was unable to grow with either methanesulfonate or methionine as the sulfur source. We therefore propose that in P. putida methionine is converted to methanethiol and then oxidized to methanesulfonate. The sulfonate is then desulfonated by alkanesulfonatase to release sulfite for reassimilation into cysteine.
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Yamagata, Shuzo, Kazuhito Ichioka, Koji Goto, Yasuko Mizuno, and Tomonori Iwama. "Occurrence of Transsulfuration in Synthesis ofl-Homocysteine in an Extremely Thermophilic Bacterium, Thermus thermophilus HB8." Journal of Bacteriology 183, no. 6 (March 15, 2001): 2086–92. http://dx.doi.org/10.1128/jb.183.6.2086-2092.2001.
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ABSTRACT A cell extract of an extremely thermophilic bacterium,Thermus thermophilus HB8, cultured in a synthetic medium catalyzed cystathionine γ-synthesis withO-acetyl-l-homoserine andl-cysteine as substrates but not β-synthesis withdl-homocysteine and l-serine (orO-acetyl-l-serine). The amounts of synthesized enzymes metabolizing sulfur-containing amino acids were estimated by determining their catalytic activities in cell extracts. The syntheses of cysthathionine β-lyase (EC 4.4.1.8 ) andO-acetyl-l-serine sulfhydrylase (EC 4.2.99.8 ) were markedly repressed by l-methionine supplemented to the medium. l-Cysteine and glutathione, both at 0.5 mM, added to the medium as the sole sulfur source repressed the synthesis ofO-acetylserine sulfhydrylase by 55 and 73%, respectively, confirming that this enzyme functions as a cysteine synthase. Methionine employed at 1 to 5 mM in the same way derepressed the synthesis of O-acetylserine sulfhydrylase 2.1- to 2.5-fold. A method for assaying a low concentration of sulfide (0.01 to 0.05 mM) liberated from homocysteine by determining cysteine synthesized with it in the presence of excess amounts of O-acetylserine and a purified preparation of the sulfhydrylase was established. The extract of cells catalyzed the homocysteine γ-lyase reaction, with a specific activity of 5 to 7 nmol/min/mg of protein, but not the methionine γ-lyase reaction. These results suggested that cysteine was also synthesized under the conditions employed by the catalysis ofO-acetylserine sulfhydrylase using sulfur of homocysteine derived from methionine. Methionine inhibitedO-acetylserine sulfhydrylase markedly. The effects of sulfur sources added to the medium on the synthesis ofO-acetylhomoserine sulfhydrylase and the inhibition of the enzyme activity by methionine were mostly understood by assuming that the organism has two proteins having O-acetylhomoserine sulfhydrylase activity, one of which is cystathionine γ-synthase. Although it has been reported that homocysteine is directly synthesized in T. thermophilus HB27 by the catalysis ofO-acetylhomoserine sulfhydrylase on the basis of genetic studies (T. Kosuge, D. Gao, and T. Hoshino, J. Biosci. Bioeng. 90:271–279, 2000), the results obtained in this study for the behaviors of related enzymes indicate that sulfur is first incorporated into cysteine and then transferred to homocysteine via cystathionine inT. thermophilus HB8.
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Sanderson, Sydney M., Peter G. Mikhael, Vijyendra Ramesh, Ziwei Dai, and Jason W. Locasale. "Nutrient availability shapes methionine metabolism in p16/MTAP-deleted cells." Science Advances 5, no. 6 (June 2019): eaav7769. http://dx.doi.org/10.1126/sciadv.aav7769.
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Codeletions of gene loci containing tumor suppressors and neighboring metabolic enzymes present an attractive synthetic dependency in cancers. However, the impact that these genetic events have on metabolic processes, which are also dependent on nutrient availability and other environmental factors, is unknown. As a proof of concept, we considered panels of cancer cells with homozygous codeletions in CDKN2a and MTAP, genes respectively encoding the commonly-deleted tumor suppressor p16 and an enzyme involved in methionine metabolism. A comparative metabolomics analysis revealed that while a metabolic signature of MTAP deletion is apparent, it is not preserved upon restriction of nutrients related to methionine metabolism. Furthermore, re-expression of MTAP exerts heterogeneous consequences on metabolism across isogenic cell pairs. Together, this study demonstrates that numerous factors, particularly nutrition, can overwhelm the effects of metabolic gene deletions on metabolism. These findings may also have relevance to drug development efforts aiming to target methionine metabolism.
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Singh, Kuldeep, and Vineet K. Singh. "Expression of Four Methionine Sulfoxide Reductases inStaphylococcus aureus." International Journal of Microbiology 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/719594.
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Staphylococcus aureuspossesses three MsrA enzymes (MsrA1, MsrA2, MsrA3) that reduce the S-epimer of methionine sulfoxide (MetO) and an MsrB enzyme that reduces R-MetO. The fourmsrgenes are expressed from three different promoters. ThemsrA1/msrBgenes are coexpressed. To determine the expression pattern ofmsrgenes, three independent reporter strains were constructed wheremsrpromoter was cloned in front of a promoterlesslacZand the resulting construct was integrated in the chromosome. Using these strains, it was determined that themsrA1/Bexpression is significantly higher inS. aureuscompared tomsrA2ormsrA3. Expression ofmsrA1/Bwas highest during stationary phase growth, but the expression ofmsrA2andmsrA3was highest during the early to midexponential growth phase. Expression ofmsrA1/Bwas induced by oxacillin and the expression ofmsrA3was upregulated by salt. Expression ofmsrA2remained unchanged under all tested conditions.
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Tiong, George K. L., and Jean E. Olley. "ENZYME IMMUNOASSAY FOR METHIONINE-ENKEPHALIN SULFOXIDE." Clinical and Experimental Pharmacology and Physiology 17, no. 7 (July 1990): 515–19. http://dx.doi.org/10.1111/j.1440-1681.1990.tb01351.x.
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Park, Insun, Erez M. Bublil, Frank Glavin, and Tomas Majtan. "Interplay of Enzyme Therapy and Dietary Management of Murine Homocystinuria." Nutrients 12, no. 9 (September 22, 2020): 2895. http://dx.doi.org/10.3390/nu12092895.
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Albeit effective, methionine/protein restriction in the management of classical homocystinuria (HCU) is suboptimal and hard to follow. To address unmet need, we developed an enzyme therapy (OT-58), which effectively corrected disease symptoms in various mouse models of HCU in the absence of methionine restriction. Here we evaluated short- and long-term efficacy of OT-58 on the background of current dietary management of HCU. Methionine restriction resulted in the lowering of total homocysteine (tHcy) by 38–63% directly proportional to a decreased methionine intake (50–12.5% of normal). Supplemental betaine resulted in additional lowering of tHcy. OT-58 successfully competed with betaine and normalized tHcy on the background of reduced methionine intake, while substantially lowering tHcy in mice on normal methionine intake. Betaine was less effective in lowering tHcy on the background of normal or increased methionine intake, while exacerbating hypermethioninemia. OT-58 markedly reduced both hyperhomocysteinemia and hypermethioninemia caused by the diets and betaine in HCU mice. Withdrawal of betaine did not affect improved metabolic balance, which was established and solely maintained by OT-58 during periods of fluctuating dietary methionine intake. Taken together, OT-58 may represent novel, highly effective enzyme therapy for HCU performing optimally in the presence or absence of dietary management of HCU.
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TAMBURRO, Antonio, Nerino ALLOCATI, Michele MASULLI, Domenico ROTILIO, Carmine DI ILIO, and Bartolo FAVALORO. "Bacterial peptide methionine sulphoxide reductase: co-induction with glutathione S-transferase during chemical stress conditions." Biochemical Journal 360, no. 3 (December 10, 2001): 675–81. http://dx.doi.org/10.1042/bj3600675.
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Peptide methionine sulphoxide reductase (MsrA; EC 1.8.4.6) is a ubiquitous enzyme catalysing the reduction of methionine sulphoxide to methionine in proteins, while the glutathione S-transferases (GSTs) are a major family of detoxification enzymes. A gene homologous to MsrA was identified in a chromosomal fragment from the bacterium Ochrobactrum anthropi, and this gene is located just downstream of a GST gene identified previously (OaGST) [Favaloro, Tamburro, Angelucci, De Luca, Melino, Di Ilio and Rotilio (1998) Biochem. J. 335, 573–579]. This raises the question of whether the products of these two genes may be involved in a common cellular protection function. To test this hypothesis, the hypothetical MsrA protein has been overexpressed in Escherichia coli as a functional 51kDa GST fusion protein. Following cleavage with thrombin and purification, the soluble 24kDa protein showed MsrA activity with N-acetylmethionine sulphoxide as substrate, as well as with other sulphoxide compounds. Therefore polyclonal antibodies were raised against the recombinant protein, and the modulation of MsrA in this bacterium, grown in the presence of different stimulants simulating several stress conditions, was investigated. The level of expression of MsrA was detected both by measuring the mRNA level and by immunoblotting experiments, in addition to measuring its catalytic activity. MsrA is a constitutive enzyme which is also inducible by chemical stress involving phenolic compounds such as phenol and 4-chlorophenol. Recently we reported that the GST of this bacterium, like MsrA, is only modulated by toxic chemical compounds [Favaloro, Tamburro, Trofino, Bologna, Rotilio and Heipieper (2000) Biochem. J. 346, 553–559]; therefore this is the first indication of a co-induction of the MsrA and GST enzymes during chemical stress.
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Pielken, P., K. L. Schimz, L. Eggeling, and H. Sahm. "Glucose metabolism in Xanthomonas campestris and influence of methionine on the carbon flow." Canadian Journal of Microbiology 34, no. 12 (December 1, 1988): 1333–37. http://dx.doi.org/10.1139/m88-234.
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The glucose flow in Xanthomonas campestris was investigated with radio-labelled glucose and by enzymological studies. Only 7% of the radioactivity was incorporated into the cell material, but 41% was oxidized to carbon dioxide and 28% transformed to xanthan. Up to 16% of cell dry weight consisted of the polysaccharide glycogen. In the presence of 2.7 mM methionine, which is an inhibitor of xanthan formation, increased carbon dioxide formation (51%) occurred. This increase was in accordance with a twofold increase in the NAD-dependent isocitrate dehydrogenase activity. The other carbon dioxide liberating enzyme, 6-P-gluconate dehydrogenase, was not influenced by methionine, but its occurrence indicates the presence of an active pentose phosphate pathway in X. campestris. Among the other enzymes detected in X. campestris was glucose dehydrogenase. The presence of this enzyme together with hexokinase indicates the operation of two different glucose metabolizing steps: one oxidative, the other phosphorylative. Only the latter directly provides phosphorylated glucose as a precursor for the activated sugars required for xanthan synthesis.
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Pampa, K. J., S. Madan Kumar, M. K. Hema, Karthik Kumara, S. Naveen, Naoki Kunishima, and N. K. Lokanath. "Crystal structure of SAM-dependent methyltransferase from Pyrococcus horikoshii." Acta Crystallographica Section F Structural Biology Communications 73, no. 12 (November 24, 2017): 706–12. http://dx.doi.org/10.1107/s2053230x17016648.
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Methyltransferases (MTs) are enzymes involved in methylation that are needed to perform cellular processes such as biosynthesis, metabolism, gene expression, protein trafficking and signal transduction. The cofactor S-adenosyl-L-methionine (SAM) is used for catalysis by SAM-dependent methyltransferases (SAM-MTs). The crystal structure of Pyrococcus horikoshii SAM-MT was determined to a resolution of 2.1 Å using X-ray diffraction. The monomeric structure consists of a Rossmann-like fold (domain I) and a substrate-binding domain (domain II). The cofactor (SAM) molecule binds at the interface between adjacent subunits, presumably near to the active site(s) of the enzyme. The observed dimeric state might be important for the catalytic function of the enzyme.
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Pantaya, D., D. Pamungkas, S. Wulandari, and M. M. D. Utami. "Fermentation of soybean meal-hydrolysates as the medium that treated by papain enzyme with Saccharomyces cerevisiae for biomass production." IOP Conference Series: Earth and Environmental Science 980, no. 1 (February 1, 2022): 012025. http://dx.doi.org/10.1088/1755-1315/980/1/012025.
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Abstract The purpose of this study was to determine the effect of soybean meal (SBM) media processing using the papain enzyme on the amino acid content and its effect on yeast biomass production. The study was divided into 2 experimental phases, first test: effect of papain enzyme hydrolysis test on amino acid in soybean meal that treated by boiling and non-boiling medium, second test: yeast biomass production was cultivated using soybean meal hydrolysates as medium with 3 treatments, namely control (- soybean meal), with soybean meal (-enzyme) and soybean meal (+enzyme). Data were analyzed using a completely randomized design with ANOVA and post hoc analysis using Tukey’s multiple range test. From the analysis, it was found that the addition of papain enzymes supplemented on soybean meal medium was affected on crude protein and amino acids composition (L-Arginine, L-proline, L-methionine, and L-phenylalanine). Enzyme treatment on SBM as substrate was increased the yeast biomass compared to control (P<0.01). In conclusion, enzyme treatment on soybean meal was improved the fermentation performance of yeast biomass production
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Cao, Zhenbo, Lorna Mitchell, Oliver Hsia, Miriam Scarpa, Stuart T. Caldwell, Arina D. Alfred, Alexandra Gennaris, Jean-François Collet, Richard C. Hartley, and Neil J. Bulleid. "Methionine sulfoxide reductase B3 requires resolving cysteine residues for full activity and can act as a stereospecific methionine oxidase." Biochemical Journal 475, no. 4 (February 28, 2018): 827–38. http://dx.doi.org/10.1042/bcj20170929.
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The oxidation of methionine residues in proteins occurs during oxidative stress and can lead to an alteration in protein function. The enzyme methionine sulfoxide reductase (Msr) reverses this modification. Here, we characterise the mammalian enzyme Msr B3. There are two splice variants of this enzyme that differ only in their N-terminal signal sequence, which directs the protein to either the endoplasmic reticulum (ER) or mitochondria. We demonstrate here that the enzyme can complement a bacterial strain, which is dependent on methionine sulfoxide reduction for growth, that the purified recombinant protein is enzymatically active showing stereospecificity towards R-methionine sulfoxide, and identify the active site and two resolving cysteine residues. The enzyme is efficiently recycled by thioredoxin only in the presence of both resolving cysteine residues. These results show that for this isoform of Msrs, the reduction cycle most likely proceeds through a three-step process. This involves an initial sulfenylation of the active site thiol followed by the formation of an intrachain disulfide with a resolving thiol group and completed by the reduction of this disulfide by a thioredoxin-like protein to regenerate the active site thiol. Interestingly, the enzyme can also act as an oxidase catalysing the stereospecific formation of R-methionine sulfoxide. This result has important implications for the role of this enzyme in the reversible modification of ER and mitochondrial proteins.
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Lievers, Karin J. A., Leo A. J. Kluijtmans, and Henk J. Blom. "Genetics of hyperhomocysteinaemia in cardiovascular disease." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 40, no. 1 (January 1, 2003): 46–59. http://dx.doi.org/10.1258/000456303321016169.
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Homocysteine, a sulphur amino acid, is a branch-point intermediate of methionine metabolism. It can be degraded in the transsulphuration pathway to cystathionine, or remethylated to methionine via the remethylation pathway. In both pathways, major genetic defects that cause enzyme deficiencies are associated with very high plasma homocysteine concentrations and excretion of homocystine into the urine. Mildly elevated plasma homocysteine concentrations are thought to be an independent and graded risk factor for both arterial occlusive disease and venous thrombosis. Genetic defects in genes encoding enzymes involved in homocysteine metabolism, or depletion of important cofactors or (co)substrates for those enzymes, including folate, vitamin B12 and vitamin B6, may result in elevated plasma homocysteine concentrations. Plasma homocysteine concentrations are also influenced by dietary and lifestyle factors. In the last decade, several studies have been conducted to elucidate the genetic determinants of hyperhomocysteinaemia in patients with cardiovascular disease. We report on both environmental and genetic determinants of hyperhomocysteinaemia and give a detailed overview of all the genetic determinants that have been reported to date.
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Wu, Cheng-Hsi, Jiunn-Liang Ko, Jiuan-Miaw Liao, Shiang-Suo Huang, Meei-Yn Lin, Ling-Hui Lee, Li-Yu Chang, and Chu-Chyn Ou. "D-methionine alleviates cisplatin-induced mucositis by restoring the gut microbiota structure and improving intestinal inflammation." Therapeutic Advances in Medical Oncology 11 (January 2019): 175883591882102. http://dx.doi.org/10.1177/1758835918821021.
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Background: There are close links between chemotherapy-induced intestinal mucositis and microbiota dysbiosis. Previous studies indicated that D-methionine was an excellent candidate for a chemopreventive agent. Here, we investigated the effects of D-methionine on cisplatin-induced mucositis. Materials and methods: Male Wistar rats (176–200 g, 6 weeks old) were given cisplatin (5 mg/kg) and treated with D-methionine (300 mg/kg). Histopathological, digestive enzymes activity, oxidative/antioxidant status, proinflammatory/anti-inflammatory cytokines in intestinal tissues were measured. Next-generation sequencing technologies were also performed to investigate the gut microbial ecology. Results: D-methionine administration increased villus length and crypt depth and improved digestive enzyme (leucine aminopeptidase, sucrose and alkaline phosphatase) activities in the brush-border membrane of cisplatin-treated rats ( p < 0.05). Furthermore, D-methionine significantly attenuated oxidative stress and inflammatory reaction and increased interleukin-10 levels in cisplatin-induced intestinal mucositis ( p < 0.05). Cisplatin administration resulted in high relative abundances of Deferribacteres and Proteobacteria and a low diversity of the microbiota when compared with control groups, D-methionine only and cisplatin plus D-methionine. Cisplatin markedly increased comparative abundances of Bacteroides caccae, Escherichia coli, Mucispirillum schaedleri, Bacteroides uniformis and Desulfovibrio C21-c20, while Lactobacillus was almost completely depleted, compared with the control group. There were higher abundances of Lactobacillus, Lachnospiraceae, and Clostridium butyrium in cisplatin plus D-methionine rats than in cisplatin rats. D-methionine treatment alone significantly increased the number of Lactobacillus reuteri. Conclusion: D-methionine protects against cisplatin-induced intestinal damage through antioxidative and anti-inflammatory effects. By enhancing growth of beneficial bacteria (Lachnospiraceae and Lactobacillus), D-methionine attenuates gut microbiome imbalance caused by cisplatin and maintains gut homeostasis.
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Alin, P., H. Jensson, E. Cederlund, H. Jörnvall, and B. Mannervik. "Cytosolic glutathione transferases from rat liver. Primary structure of class alpha glutathione transferase 8-8 and characterization of low-abundance class Mu glutathione transferases." Biochemical Journal 261, no. 2 (July 15, 1989): 531–39. http://dx.doi.org/10.1042/bj2610531.
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Six GSH transferases with neutral/acidic isoelectric points were purified from the cytosol fraction of rat liver. Four transferases are class Mu enzymes related to the previously characterized GSH transferases 3-3, 4-4 and 6-6, as judged by structural and enzymic properties. Two additional GSH transferases are distinguished by high specific activities with 4-hydroxyalk-2-enals, toxic products of lipid peroxidation. The most abundant of these two enzymes, GSH transferase 8-8, a class Alpha enzyme, has earlier been identified in rat lung and kidney. The amino acid sequence of subunit 8 was determined and showed a typical class Alpha GSH transferase structure including an N-acetylated N-terminal methionine residue.
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Aoki, Y., M. Yamamoto, S. M. Hosseini-Mazinani, N. Koshikawa, K. Sugimoto, and M. Arisawa. "Antifungal azoxybacilin exhibits activity by inhibiting gene expression of sulfite reductase." Antimicrobial Agents and Chemotherapy 40, no. 1 (January 1996): 127–32. http://dx.doi.org/10.1128/aac.40.1.127.
Full textAbstract:
Azoxybacilin, produced by Bacillus cereus, has a broad spectrum of antifungal activity in methionine-free medium and has been suggested to inhibit sulfite fixation. We have further investigated the mode of action by which azoxybacilin kills fungi. The compound inhibited the incorporation of [35S] sulfate into acid-insoluble fractions of Saccharomyces cerevisiae under conditions in which virtually no inhibition was observed for DNA, RNA, or protein synthesis. It did not interfere with the activity of the enzymes for sulfate assimilation but clearly inhibited the induction of those enzymes when S. cerevisiae cells were transferred from rich medium to a synthetic methionine-free medium. Particularly strong inhibition was observed in the induction of sulfite reductase. Northern (RNA) analysis revealed that azoxybacilin decreased the level of mRNA of genes for sulfate assimilation, including MET10 for sulfite reductase and MET4, the transactivator of MET10 and other sulfate assimilation genes. When activities of azoxybacilin were compared for mRNA and enzyme syntheses from MET10, the concentration required for inhibition of transcription of the gene was about 10 times higher (50% inhibitory concentration = 30 micrograms/ml) than that required for inhibition of induction of enzyme synthesis (50% inhibitory concentration = 3 micrograms/ml). The data suggest that azoxybacilin acts on at least two steps in the expression of sulfite reductase; the transcriptional activation of MET4 and a posttranscriptional regulation in MET10 expression. We conclude that azoxybacilin exhibits antifungal activity by interfering with the regulation of expression of sulfite reductase activity.
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Gingras, D., D. Boivin, and R. Beliveau. "Asymmetrical distribution of l-isoaspartyl protein carboxyl methyltransferases in the plasma membranes of rat kidney cortex." Biochemical Journal 297, no. 1 (January 1, 1994): 145–50. http://dx.doi.org/10.1042/bj2970145.
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We have studied the distribution of membrane-associated L-isoaspartyl protein carboxyl methyltransferases (PCMTs) in plasma membranes purified from rat kidney cortex. Addition of CHAPS to brush-border membranes (BBM) and basolateral membranes (BLM) was required to measure optimal membrane-dependent methylation of ovalbumin and TS-isoD-YSKY, substrates of L-isoaspartyl PCMTs. Extraction of both membrane-associated enzymes was achieved with detergents, but not with high-salt solutions, suggesting a strong membrane attachment. However, upon phase partitioning using Triton X-114, both enzymes were predominantly associated with the detergent-poor phase, suggesting a relatively hydrophilic nature. The enzymes showed similar catalytic properties such as substrate recognition and affinity towards the methyl donor, S-adenosyl-L-methionine. The activity of the BBM enzyme, however, was about 2-fold higher than that of the BLM enzyme. Identification of the endogenous substrates located in the two plasma membranes by acidic gel electrophoresis in the presence of a cationic detergent revealed significant differences in the methyl-accepting proteins of both membranes. The BBM-methylated proteins had sizes of 35, 50 and 54 kDa, whereas the major BLM-methylated substrates were of 97 and 100 kDa. The enzymes showed distinct behaviour on Mono Q anion-exchange chromatography. The BBM-associated PCMT did not bind to the column, being eluted in the flow-through, whereas the BLM enzyme bound to the column and was eluted at 0.15 M NaCl. Moreover, the two enzymes had different molecular masses under both denaturing and nondenaturing conditions, the BLM PCMT migrating at an apparent molecular mass of 29 kDa, compared with 27 kDa for the BBM enzyme. Taken together, these results show the presence of two distinct L-isoaspartyl PCMTs in the plasma membranes of the kidney cortex.
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Dias, Benjamin, and Bart Weimer. "Purification and Characterization ofl-Methionine γ-Lyase from Brevibacterium linens BL2." Applied and Environmental Microbiology 64, no. 9 (September 1, 1998): 3327–31. http://dx.doi.org/10.1128/aem.64.9.3327-3331.1998.
Full textAbstract:
ABSTRACT l-Methionine γ-lyase (EC 4.4.1.11 ) was purified to homogeneity from Brevibacterium linens BL2, a coryneform bacterium which has been used successfully as an adjunct bacterium to improve the flavor of Cheddar cheese. The enzyme catalyzes the α,γ elimination of methionine to produce methanethiol, α-ketobutyrate, and ammonia. It is a pyridoxal phosphate-dependent enzyme, with a native molecular mass of approximately 170 kDa, consisting of four identical subunits of 43 kDa each. The purified enzyme had optimum activity at pH 7.5 and was stable at pHs ranging from 6.0 to 8.0 for 24 h. The pure enzyme had its highest activity at 25°C but was active between 5 and 50°C. Activity was inhibited by carbonyl reagents, completely inactivated by dl-propargylglycine, and unaffected by metal-chelating agents. The pure enzyme had catalytic properties similar to those of l-methionine γ-lyase fromPseudomonas putida. Its Km for the catalysis of methionine was 6.12 mM, and its maximum rate of catalysis was 7.0 μmol min−1 mg−1. The enzyme was active under salt and pH conditions found in ripening Cheddar cheese but susceptible to degradation by intracellular proteases.
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Ejim, Linda J., Vanessa M. D'Costa, Nadine H. Elowe, J. Concepción Loredo-Osti, Danielle Malo, and Gerard D. Wright. "Cystathionine β-Lyase Is Important for Virulence of Salmonella enterica Serovar Typhimurium." Infection and Immunity 72, no. 6 (June 2004): 3310–14. http://dx.doi.org/10.1128/iai.72.6.3310-3314.2004.
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ABSTRACT The biosynthesis of methionine in bacteria requires the mobilization of sulfur from Cys by the formation and degradation of cystathionine. Cystathionine β-lyase, encoded by metC in bacteria and STR3 in Schizosaccharomyces pombe, catalyzes the breakdown of cystathionine to homocysteine, the penultimate step in methionine biosynthesis. This enzyme has been suggested to be the target for pyridinamine antimicrobial agents. We have demonstrated, by using purified enzymes from bacteria and yeast, that cystathionine β-lyase is not the likely target of these agents. Nonetheless, an insertional inactivation of metC in Salmonella enterica serovar Typhimurium resulted in the attenuation of virulence in a mouse model of systemic infection. This result confirms a previous chemical validation of the Met biosynthetic pathway as a target for the development of antibacterial agents and demonstrates that cystathionine β-lyase is important for bacterial virulence.
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Thorgersen, Michael P., and Diana M. Downs. "Oxidative stress and disruption of labile iron generate specific auxotrophic requirements in Salmonella enterica." Microbiology 155, no. 1 (January 1, 2009): 295–304. http://dx.doi.org/10.1099/mic.0.020727-0.
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The response of a cell to integrated stresses was investigated using environmental and/or genetic perturbations that disrupted labile iron homeostasis and increased oxidative stress. The effects of the perturbations were monitored as nutritional requirements, and were traced to specific enzymic targets. A yggX gshA cyaY mutant strain required exogenous thiamine and methionine for growth. The thiamine requirement, which had previously been linked to the Fe–S cluster proteins ThiH and ThiC, was responsive to oxidative stress and was not directly affected by manipulation of the iron pool. The methionine requirement was associated with the activity of sulfite reductase, an enzyme that appeared responsive to disruption of labile iron homeostasis. The results are incorporated in a model to suggest how the activity of iron-containing enzymes not directly sensitive to oxygen can be decreased by oxidation of the labile iron pool.
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Riches, D. W., and P. M. Henson. "Bacterial lipopolysaccharide suppresses the production of catalytically active lysosomal acid hydrolases in human macrophages." Journal of Cell Biology 102, no. 5 (May 1, 1986): 1606–14. http://dx.doi.org/10.1083/jcb.102.5.1606.
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Sub-microgram quantities of bacterial lipopolysaccharide (LPS) have been found to substantially reduce the intracellular catalytic activities of three representative lysosomal enzymes (namely, acid phosphatase, hexosaminidase, and beta-glucuronidase) in human monocyte-derived macrophages. This response was not associated with a concurrent increase in enzyme catalytic activity in the culture supernatant, and hence, could not be explained by mobilization of preformed material. By conducting experiments in the presence and absence of indomethacin, a cyclooxygenase inhibitor, the reduction in lysosomal enzyme catalytic activities was shown not to be dependent on the ability of LPS to induce prostaglandin E2 production. The response was not found to be the result of a more generalized LPS-dependent reduction in the ability of the cells to synthesize protein, since the presence of LPS in macrophage cultures did not appreciably affect the amount of [35S]methionine incorporated into total cellular proteins. A kinetic analysis of the effect of LPS on the down-regulation of enzyme catalytic activities indicated that this was an early response of the cells to LPS exposure. An investigation of the effects of blockade of enzyme catabolism (using the lysosomotropic weak-base, methylamine) indicated that the reduction of catalytic enzyme activities in response to LPS was probably due to a decreased rate of production of active product, rather than an enhanced rate of enzyme catabolism. This suggestion was confirmed by experiments in which the synthesis of pro-hexosaminidase (measured by biosynthetic labeling with [35S]methionine and specific immunoprecipitation of labeled pro-hexosaminidase) was found to be reduced by 42% after a 24-h exposure to LPS (although the synthesis of complement component C3 was stimulated by a factor of 4.5). It is suggested that the ability of LPS to regulate the functional expression of protein products contributes to changes in the overall functional status of these cells in response to this bacterial product.
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Black, M. T., S. A. White, G. A. Reid, and S. K. Chapman. "High-level expression of fully active yeast flavocytochrome b2 in Escherichia coli." Biochemical Journal 258, no. 1 (February 15, 1989): 255–59. http://dx.doi.org/10.1042/bj2580255.
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Wild-type flavocytochrome b2 (L-lactate dehydrogenase) from the yeast Saccharomyces cerevisiae and three singly substituted mutant forms (F254, R349 and K376) have been expressed in the bacterium Escherichia coli. The enzyme expressed in E. coli contains the protohaem IX and flavin mononucleotide (FMN) prosthetic groups found in the enzyme isolated from yeast, has an electronic absorption spectrum identical with that of the yeast protein and an identical Mr value of 57,500 estimated by SDS/polyacrylamide-gel electrophoresis. N-Terminal amino-acid-sequence data indicate that the flavocytochrome b2 isolated from E. coli begins at position 6 (methionine) when compared with mature flavocytochrome b2 from yeast. The absence of the first five amino acid residues appears to have no effect on the enzyme-catalysed oxidation of L-lactate, since Km values for the yeast- and E. coli-expressed wild-type enzymes were identical within experimental error. The F254 mutant enzyme expressed in E. coli also showed kinetic parameters essentially the same as those found for the enzyme from yeast. The R349 and K376 mutant enzymes had no activity when expressed in either yeast or E. coli. The yield of flavocytochrome b2 from E. coli is estimated to be between 500- and 1000-fold more than from a similar wet weight of yeast (this high level of expression results in E. coli cells which are pink in colour). The increased yield has allowed us to verify the presence of FMN in the R349 mutant enzyme. The advantages of E. coli as an expression system for flavocytochrome b2 are discussed.
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Amir, Rachel, Hagai Cohen, and Yael Hacham. "Revisiting the attempts to fortify methionine content in plant seeds." Journal of Experimental Botany 70, no. 16 (March 26, 2019): 4105–14. http://dx.doi.org/10.1093/jxb/erz134.
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Abstract The sulfur-containing amino acid methionine belongs to the group of essential amino acids, meaning that humans and animals must consume it in their diets. However, plant seeds have low levels of methionine, limiting their nutritional potential. For this reason, efforts have been made over the years to increase methionine levels in seeds. Here, we summarize these efforts and focus particularly on those utilizing diverse genetic and molecular tools. Four main approaches are described: (i) expression of methionine-rich storage proteins in a seed-specific manner to incorporate more soluble methionine into the protein fraction; (ii) reduction of methionine-poor storage proteins inside the seeds to reinforce the accumulation of methionine-rich proteins; (iii) silencing methionine catabolic enzymes; and (iv) up-regulation of key biosynthetic enzymes participating in methionine synthesis. We focus on the biosynthetic genes that operate de novo in seeds and that belong to the sulfur assimilation and aspartate family pathways, as well as genes from the methionine-specific pathway. We also include those enzymes that operate in non-seed tissues that contribute to the accumulation of methionine in seeds, such as S-methylmethionine enzymes. Finally, we discuss the biotechnological potential of these manipulations to increase methionine content in plant seeds and their effect on seed germination.