Relevant bibliographies by topics / Methionase enzyme

Academic literature on the topic 'Methionase enzyme'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Contents

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Methionase enzyme.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Methionase enzyme"

1

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
2

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.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
4

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
5

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
6

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
7

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
8

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
9

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
10

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.

Full text
Abstract:
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.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "Methionase enzyme"

1

Lou, Xiao. "Biochemical and structural studies of human methionine synthase reductase." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/biochemical-and-structural-studies-of-human-methionine-synthase-reductase(822952fc-8bef-4a30-9221-7fb154638193).html.

Full text
Abstract:
Human methionine synthase reductase (MSR) is a 78-kDa diflavin enzyme involved in folate and methionine metabolism. It regenerates the cofactor of methionine synthase (MS), cob(II), to reduce inactive MS. MSR and one of its the FAD/NADPH binding domain were cloned as GST-tagged fusion proteins for expression and purification in Escherichia coli. And a 1.9 Å Crystals of the FAD/NADPH binding domain of MSR with and without NADP+ were produced and carried out X-ray diffraction experiment and the structure of the crystal was solved by molecule replacement method. The activation domain of human MS was also expressed and purified in Escherichia coli and crystallization conditions determined. A new expression vector for full-length MSR, which contains a N-terminal GST tag, and C-terminal 6× His tag, was constructed and validated by sequencing, restriction enzymes digestion and successfully expressed in E. coli and Yeast Pichia pastoris. Based on the structure information, site-directed mutagenesis on the two positions Asp652 and trpytophan697 of MSR were designed and completed. The variants D652A, D652R, D652N of the FAD/NADPH binding domain of MSR and the variants D652A,D652R,D652N, W696A,W697H of the full-length MSR were cloned and expressed in BL21 (E. coli). The proteins of these mutants were purified by affinity chromatography, anion exchange chromatography and gel filtration chromatography. And the kinetic studies on these variants of MSR were investigated in steady state kinetic study, steady state inhibition studies, stopped-flow pre steady-state kinetic and redox potential studies. Compared with the data of the wild type MSR, the turnover number of variants all decreased, the catalytic ability become lower and the midpoint potential of cofactor FAD occurred positive shift. Both 2'5-ADP and NADP+ were competitive inhibitors for variants of MSR. However, 2'5'-ADP was relative strong inhibitor than NADP+. All the data on variants of MSR suggested the Asp652 and tryptophan697 were two important structural and function determinant of MSR. To investigate the dynamic properties of EPR, ENDOR and ESMME are used to investigate the existence of the semiquinone flavin cofactors, FAD and FMN, and the hyperfine coupling arising from the interaction of some nuclei with the unpaired electron spin. ELDOR spectroscopy was applied to measure the distance between the FAD and FMN in MSR under the binding of 2', 5'-ADP, NADP and the activation domain of MS to further check the conformational change of MSR.
APA, Harvard, Vancouver, ISO, and other styles
2

Dhouib, Rabeb, Dk Seti Maimonah Pg Othman, Victor Lin, Xuanjie J. Lai, Hewa G. S. Wijesinghe, Ama-Tawiah Essilfie, Amanda Davis, et al. "A Novel, Molybdenum-Containing Methionine Sulfoxide Reductase Supports Survival of Haemophilus influenzae in an In vivo Model of Infection." FRONTIERS MEDIA SA, 2016. http://hdl.handle.net/10150/622464.

Full text
Abstract:
Haemophilus influenzae is a host adapted human mucosal pathogen involved in a variety of acute and chronic respiratory tract infections, including chronic obstructive pulmonary disease and asthma, all of which rely on its ability to efficiently establish continuing interactions with the host. Here we report the characterization of a novel molybdenum enzyme, TorZ/MtsZ that supports interactions of H. influenzae with host cells during growth in oxygen-limited environments. Strains lacking TorZ/MtsZ showed a reduced ability to survive in contact with epithelial cells as shown by immunofluorescence microscopy and adherence/invasion assays. This included a reduction in the ability of the strain to invade human epithelial cells, a trait that could be linked to the persistence of H. influenzae. The observation that in a murine model of H. influenzae infection, strains lacking TorZ/MtsZ were almost undetectable after 72 h of infection, while similar to 3.6 x 10(3) CFU/mL of the wild type strain were measured under the same conditions is consistent with this view. To understand how TorZ/MtsZ mediates this effect we purified and characterized the enzyme, and were able to show that it is an S- and N-oxide reductase with a stereospecificity for S-sulfoxides. The enzyme converts two physiologically relevant sulfoxides, biotin sulfoxide and methionine sulfoxide (MetSO), with the kinetic parameters suggesting that MetSO is the natural substrate of this enzyme. TorZ/MtsZ was unable to repair sulfoxides in oxidized Calmodulin, suggesting that a role in cell metabolism/energy generation and not protein repair is the key function of this enzyme. Phylogenetic analyses showed that H. influenzae TorZ/MtsZ is only distantly related to the Escherichia colt TorZ TMAO reductase, but instead is a representative of a new, previously uncharacterized Glade of molybdenum enzyme that is widely distributed within the Pasteurellaceae family of pathogenic bacteria. It is likely that MtsZ/TorZ has a similar role in supporting host/pathogen interactions in other members of the Pasteurellaceae, which includes both human and animal pathogens.
APA, Harvard, Vancouver, ISO, and other styles
3

Sampson, Peter B. "Synthesis of potential inhibitors targeting enzymes involved in methionine biochemistry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ53511.pdf.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Huber, Tyler D. "TOWARD AN ENZYME-COUPLED, BIOORTHOGONAL PLATFORM FOR METHYLTRANSFERASES: PROBING THE SPECIFICITY OF METHIONINE ADENOSYLTRANSFERASES." UKnowledge, 2019. https://uknowledge.uky.edu/pharmacy_etds/106.

Full text
Abstract:
Methyl group transfer from S-adenosyl-l-methionine (AdoMet) to various substrates including DNA, proteins, and natural products (NPs), is accomplished by methyltransferases (MTs). Analogs of AdoMet, bearing an alternative S-alkyl group can be exploited, in the context of an array of wild-type MT-catalyzed reactions, to differentially alkylate DNA, proteins, and NPs. This technology provides a means to elucidate MT targets by the MT-mediated installation of chemoselective handles from AdoMet analogs to biologically relevant molecules and affords researchers a fresh route to diversify NP scaffolds by permitting the differential alkylation of chemical sites vulnerable to NP MTs that are unreactive to traditional, synthetic organic chemistry alkylation protocols. The full potential of this technology is stifled by several impediments largely deriving from the AdoMet-based reagents, including the instability, membrane impermeability, poor synthetic yield and resulting diastereomeric mixtures. To circumvent these main liabilities, novel chemoenzymatic strategies that employ methionine adenosyltransferases (MATs) and methionine (Met) analogs to synthesize AdoMet analogs in vitro were advanced. Unstable AdoMet analogs are simultaneously utilized in a one-pot reaction by MTs for the alkylrandomization of NP scaffolds. As cell membranes are permeable to Met analogs, this also sets the stage for cell-based and, potentially, in vivo applications. In order to further address the instability of AdoMet and analogs thereof, MAT-catalyzed reactions utilizing Met and ATP isosteres generated highly stable AdoMet isosteres that were capable of downstream utilization by MTs. Finally, the development, use, and results of a high-throughput screen identified mutant-MAT/Met-analog pairs suitable for postliminary bioorthogonal applications.
APA, Harvard, Vancouver, ISO, and other styles
5

Velichkova, Polina. "Modeling of methyl transfer reactions in S-Adenosyl-L-Methionine dependent enzymes." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3910.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Gagliano, Elisa. "A Bioinformatics Approach to Identifying Radical SAM (S-Adenosyl-L-Methionine) Enzymes." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98736.

Full text
Abstract:
Radical SAM enzymes are ancient, essential enzymes. They perform radical chemical reactions in virtually all living organisms and are involved in producing antibiotics, generating greenhouse gases, human health, and likely many other essential roles that have yet to be established. A wide variety of reactions have been characterized from this group of enzymes, including hydrogen abstractions, the transferring of methylthio groups, complex cyclization and rearrangement reactions, and others. However, many radical SAM enzymes have yet to be identified or characterized. There have been great leaps forward in the amount of enzyme sequences that are available in public databases, but experiments to investigate what chemical reactions the enzymes perform take a great deal of time. In our work, we utilize Hidden Markov Models to identify possible radical SAM enzymes and predict their possible functions through BLAST alignments and homology modelling. We also explore their distribution across the tree of life and determine how it is correlated with organism oxygen tolerances, because the core iron-sulfur cluster is oxygen sensitive. Trends in the abundances of radical SAM enzymes depending on oxygen tolerances were more apparent in prokaryotes than in eukaryotes. Although eukaryotes tend to have fewer radical SAM enzymes than prokaryotes, we were able to analyze uncharacterized radical SAM enzymes from both an aerobic eukaryote (Entamoeba histolytica) and a eukaryote capable of oxygenic photosynthesis (Gossypium barbadense), and predict the reactions they catalyze. This work sets the stage for the functional characterization of these essential yet elusive enzymes in future laboratory experiments.
Master of Science in Life Sciences
Radical SAM enzymes are ancient, essential enzymes that perform chemical reactions in virtually all living organisms. We do know that they are involved in producing antibiotics, human health, and generating greenhouse gases. We also know that there are many radical SAM enzymes whose functions remain a mystery. There have been great leaps forward in the amount of enzyme sequences that are available in public databases, but experiments to investigate what chemical reactions enzymes perform take a great deal of time. The experiments are especially difficult for radical SAM enzymes because the oxygen we breathe can break the enzymes down in a laboratory. In our work, we utilize computational techniques to identify possible radical SAM enzymes and predict what reactions they might catalyze. Because these enzymes are vulnerable to oxygen in laboratory environments, we also explore whether organisms that breathe oxygen have fewer of these enzymes than organisms that perform anaerobic respiration instead. We found that does seem to be the case in microbes like bacteria and archaea, but the results were not as consistent for eukaryotes. We then chose radical SAM enzymes we had identified from both an aerobic eukaryote (Entamoeba histolytica) and a eukaryote capable of producing oxygen (Gossypium barbadense), and predicted the reactions they catalyze. This work sets the stage for the functional characterization of these essential yet elusive enzymes in future laboratory experiments.
APA, Harvard, Vancouver, ISO, and other styles
7

Yanamadala, Srinivasa Rao. "Molecular cloning and characterization of regulatory enzymes in threonine biosynthetic pathway from soybean." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4932.

Full text
Abstract:
Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 12, 2009) Includes bibliographical references.
APA, Harvard, Vancouver, ISO, and other styles
8

Johnson, Bernadette. "Fluorinated #alpha#-amino acid analogues of L-methionine and related compounds for use as potential enzyme inhibitors." Thesis, University of Glasgow, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264261.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Young, Anthony Peter, and Anthony Peter Young. "Characterization of 4-demethylwyosine Synthase, a Radical S-adenosyl-l-methionine Enzyme Involved in the Modification of tRNA." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621437.

Full text
Abstract:
Wyosine derivatives are highly complex modified ribonucleic acid (RNA) bases found in archaea and eukarya. They are a modification of a genetically encoded guanosine found at position 37 of phenylalanine encoding transfer ribonucleic acid (tRNA). The second step in the biosynthesis of all wyosine derivatives, in both archaea and eukarya, is the transformation of N-methylguanosine to 4-demethylwyosine by the radical S-adenosyl-l-methionine enzyme TYW1. When these studies were initiated, the substrate of TYW1 was unknown. Four possible substrates; acetyl CoA, acetyl phosphate, phosphoenolpyruvate, and pyruvate; were tested for activity. Only incubation with pyruvate led to production of 4-demethylwyosine. As only two new carbons are incorporated into the RNA base at this step, ¹³C isotopologues were used to identify the carbons that are transferred into 4-demethylwyosine. These experiments revealed that C2 and C3 of pyruvate are incorporated into 4-demethylwyosine, with C1 lost as an unknown byproduct. Utilizing pyruvate containing deuteriums in place of protons on the C3 carbon, the regiochemistry of the addition was determined. It was found that C3 forms the methyl group of 4-demethylwyosine and C2 becomes the bridging carbon in the imidazoline ring. The site of hydrogen atom abstraction by 5'-deoxyadenosyl radical was identified as the N-methylguanosine methyl group through the use of tRNA containing a deuterated methyl group. The putative mechanism for this transformation involved the formation of an enzyme substrate Schiff base through a conserved lysine residue. Utilizing sodium cyanoborohydride a Schiff base was trapped between TYW1 and pyruvate. The mass of the trapped adduct responded as expected when different isotopologues of pyruvate were used, demonstrating that it is due to pyruvate. Moreover, the fragment of TYW1 that contained the trapped adduct contained two lysine residues, one of which was shown to be required for activity both in vivo and in vitro. It was initially proposed that TYW1 contained two iron-sulfur clusters, and then subsequently shown to have two 4Fe-4S clusters. Site directed mutagenesis, along with iron and sulfide analysis identified the cysteines; as C26, C39, and C52; coordinating the second 4Fe-4S cluster. This study identified pyruvate as the substrate of TYW1, and provided evidence for key steps in the transformation of N-methylguanosine to 4-demethylwyosine.
APA, Harvard, Vancouver, ISO, and other styles
10

Wang, Xiao Suo. "A novel ELISA to detect methionine sulfoxide-containing apolipoprotein A-I." Connect to full text, 2009. http://hdl.handle.net/2123/5423.

Full text
Abstract:
Thesis (Ph. D.)--University of Sydney, 2009.
Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Discipline of Pathology, Faculty of Medicine. Title from title screen (viewed Sept. 30, 2009) Includes bibliography. Also available in print form.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Books on the topic "Methionase enzyme"

1

Briddon, Anthony. Approach to the Patient with Hyperhomocysteinemia. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199972135.003.0079.

Full text
Abstract:
Hyperhomocysteinaemia (HHC) may occur as a result of a variety of inherited and acquired conditions ranging from mild and benign to severe and life threatening, and there is a higher probability that they will first manifest during early adulthood rather than infancy, with acquired forms commonly presenting into old age. Milder forms of HHC may exist without homocystinuria, and screening tests relying on the presence of homocystine in the urine will give a false negative result. Methylcobalamin is an essential cofactor for methionine synthase, a key enzyme in the homocysteine remethylation pathway: consequently, investigation for inherited abnormalities of intracellular B12 metabolism forms an integral part of the biochemical investigation of HHC. Additionally, there are acquired forms of HHC, notably those involving vitamin B12 deficiency and malabsorption. Mild to moderate HHC has also been associated with alcohol abuse, excessive caffeine intake, hypothyroidism, and poor renal function.
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Methionase enzyme"

1

Schomburg, Dietmar, and Margit Salzmann. "Methionine decarboxylase." In Enzyme Handbook 1, 233–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-86605-0_53.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Schomburg, Dietmar, and Dörte Stephan. "Methionine adenosyltransferase." In Enzyme Handbook 13, 23–30. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-59176-1_6.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Schomburg, Dietmar, and Margit Salzmann. "Methionine gamma-lyase." In Enzyme Handbook 1, 1097–101. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-86605-0_246.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Schomburg, Dietmar, and Dörte Stephan. "Methionine S-methyltransferase." In Enzyme Handbook 11, 53–55. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61030-1_12.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Schomburg, Dietmar, and Dörte Stephan. "Methionine-glyoxylate transaminase." In Enzyme Handbook 13, 535–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-59176-1_108.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Schomburg, D., M. Salzmann, and D. Stephan. "Methionine-S-oxide reductase." In Enzyme Handbook 7, 583–85. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78521-4_113.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Schomburg, Dietmar, and Dörte Stephan. "D-Methionine-pyruvate transaminase." In Enzyme Handbook 13, 387–89. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-59176-1_77.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Schomburg, D., M. Salzmann, and D. Stephan. "Protein-methionine-S-oxide reductase." In Enzyme Handbook 7, 587–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78521-4_114.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Sahoo, Smruti Malinee, and Sabuj Sahoo. "l-Asparaginase and Methioninase as Prospective Anticancer Enzymes: Current Applications and Production Approaches." In Bioprospecting of Enzymes in Industry, Healthcare and Sustainable Environment, 349–62. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4195-1_16.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Lundahl, Maike N., Brigitta Nemeth, William E. Broderick, and Joan B. Broderick. "Radical S-Adenosyl-l-Methionine Enzymes." In Comprehensive Coordination Chemistry III, 124–33. Elsevier, 2021. http://dx.doi.org/10.1016/b978-0-08-102688-5.00109-4.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Methionase enzyme"

1

Wilder, Carly S., Achinto Saha, George Georgiou, Everett Stone, and John DiGiovanni. "Abstract 2996: Systemic depletion of L-methionine with an engineered human enzyme for the treatment of melanoma." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.am2019-2996.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Wilder, Carly S., Achinto Saha, George Georgiou, Everett Stone, and John DiGiovanni. "Abstract 2996: Systemic depletion of L-methionine with an engineered human enzyme for the treatment of melanoma." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-2996.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Zhu, X., AC Otto, H. Gan-Schreier, Y. Cheng, S. Tuma-Kellner, A. Ganzha, G. Liebisch, and W. Chamulitrat. "iPLA2beta Deficiency in mice fed methionine-choline-deficient diet does not protect hepatic steatosis but still attenuates hepatic fatty acids, cholesterol esters, and liver enzymes." In 35. Jahrestagung der Deutschen Arbeitsgemeinschaft zum Studium der Leber. Georg Thieme Verlag KG, 2019. http://dx.doi.org/10.1055/s-0038-1677193.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Standen, G., P. Moodie, H. Pannekoek, C. L. Verweij, and I. R. Peake. "ANALYSIS OF THE VON WILLEBRAND FACTOR (vWF) GENE IN 6 PATIENTS WITH SEVERE TYPE III VON WILLEBRANDS DISEASE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644641.

Full text
Abstract:
DNA from 6 unrelated patients with severe type III von Willebrands disease (vWF antigen < 0.01u/dl) was studied with a cDNA probe for the 3' end of the vWF gene. DNA was extracted from peripheral blood leucocytes using standard techniques and was digested with a range of restriction enzymes. DNA fragments were separated by electrophoresis in 0.7% agarose and were southern blotted onto hybond-N (Amersham). The probe used was pvWF1100, a 1.1kb PstI fragment derived from the 2.28kb vWFcDNA insert of pvWF2280 isolated from a human endothelial cell cDNA expression library (Verweij et al, Nucleic Acids Res 13 (1985) 4699-4717). The probe corresponds to nucleotides 7083 to 8191 of the vWF cDNA (first nucleotide of initiator methionine as 1).When digested with Bglll and probed with pvWF11000, normal DNA showed two invariant bands (13 and 4.9kb) and polymorphic bands of 9 and/or 7.4kb. This pattern was also seen in 5 of the 6 severe vWD patients DNA suggesting that in this 3' area of the gene they had no major deletions or rearrangements. In the 6th case however the band of 4.9kb was not seen and did not appear to be replaced by any novel fragments, suggesting a partial deletion including some of the 3' end of the gene. This patient had the clinically severest form of the condition in that the patient had developed, some 10 years ago, an antibody (inhibitor) to vWF as detected by the ability of the patients plasma to inhibit restocetin cofactor activity in normal plasma. His parents were related (his mother was his father's second cousin) and had levels of vWFAg, considerably lower than those of factor VIII activity. This situation has been previously reported in carriers of recessive severe vWD. vWD was also present in a second family member, but in a less severe form (vWFAg 3u/dl). This patient and all other members of the family have, to date, given normal restriction fragment patterns with the vWF probe and several enzymes, including BgIII.
APA, Harvard, Vancouver, ISO, and other styles
5

Colman, R. W., A. Gewirtz, D. L. Wang, M. M. Huh, B. P. Schick, P. K. Schick, and C. L. Shapiro. "BIOSYNTHESIS AND EXPRESSION OF FACTOR V IN MAGAKARYOCYTES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642955.

Full text
Abstract:
Coagulation factor V (FV), is a single chain, multifunctional glycoprotein of Mr 350,000 which interacts with a variety of hemostatic proteins such as factor Xa, prothrombin, thrombin and protein C, on the surface of platelets and vascular endothelial cells. FV serves as both a cofactor and substrate in the generation of thrombin and plays a critical regulatory role in both physiologic hemostasis and pathologic thrombosis. The biosynthesis of FV and its subsequent expression are therefore expected to be precisely controlled and may differ in the three sites of synthesis - hepatocytes, endothelial cells, and megakaryocytes (MK). We have previously demonstrated that each guinea pig MK contains 500 times as much FV as in a platelet, as quantified by a competitive enzyme-linked-immunosorbent assay and expresses FV by cytoimmunofluorescence. De novo biosynthesis was demonstrated by incorporation of S-methionine into FV purified on a immunoaffinity column. The purified MK protein exhibited both FV coagulant activity and antigenicity. However, MK FV was more slowly activated by thrombin, more stable in the absence of Ca and exhibited a slightly higher M of 380,000 compared to plasma FV. Similar studies have documented biosynthesis in human MK. In addition, all morphologically recognizable MK enriched by elutriation from human bone marrow contained FV as documented by both monospecific polyclonal and monoclonal antibodies (MAb) to FV. All these cells bound FV since a murine MAb reacting with the light chain of FV (B38) labeled all cells. In contrast, 68% of cells synthesized FV since B10, a MAb to the activation peptide recognizing FV but not FVa, labeled this fraction. To determine whether immature nonnorphologically recognizable MK expressed FV, we identified these cells with an antiserum to human platelet glycoproteins and then probed them with B38. Seventy percent (70%) of such small cells expressed FV. In contrast, no small cells in MK colonies cloned in FV deficient medium expressed FV while only 40% of such colonies contained cells which expressed FV.To further probe the regulation of FV in MK we attempted to correlate the synthesis of FV as probed by MAb B10 with geometric mean cell diameter, stage and ploidy. No significant correlation of FV with any of these indicators of MK maturation. In contrast, preliminary studies suggest that low doses of tetradecanoyl phorbol acetate augment both the number of MK containing FV and the level of FV expressed by individual cells. Thus, FV synthesis may be regulated independent of size, stage, or ploidy and protein kinase C may play a role.To further define the molecular nature of FV in MK we found that purified FV was converted from a monomer to high Mr multimers by an enzyme derived from MK. These multimers resulting from covalent crosslinking since they were stable to SDS, 100° C and reducing agents. The responsible enzyme appeared to be MK FXIIIa since it required C, was inhibited by agents which react with the active site thiol group and was blocked by pseudoamine donor substrates such as putrescine. In addition, FXIIIa was directly demonstrated in guinea pig MK by a specific activity stain. Other investigators have established that FV became irreversibly associated with platelet cytoskeletons after exposure to thrombin. tested whether FXIIIa might mediate this association by performing ligand blotting of platelet membrane proteins using 125I-FV(FV*). Only actin of all the membrane proteins was detected by radioautography. The binding of FV* to the cytoskeleton was dependent in the presence of Ca and FXIIIa. In purified systems crosslinked complexes containing FV* or radiolabeled actin were detected in separate experiments. In whole platelets, the formation of the heteropolymer, after thrombin stimulation, was inhibited by antibodies to FXIII a chain, FV activation peptide (B10) or actin. Endogenous platelet FV was also dependent on FXIII for incorporation into the platelet cytoskeleton after thrombin stimulation. When thrombin-treated FV was crosslinked to actin only the activation peptide (150 kDa) was crosslinked. The light chain or heavy chain of FVa were not involved. Thus FXIIIa play an important role in the binding of FV in platelets to the cytoskeleton during activation and secretion.Further studies of FV in megakaryocytes are necessary to define the regulation of biosynthesis and the control of expression which dictate its critical role in hemostasis and thrombosis.
APA, Harvard, Vancouver, ISO, and other styles

Reports on the topic "Methionase enzyme"

1

So, Joanne D. An Essential Protein Repair Enzyme: Investigation of the Molecular Recognition Mechanism of Methionine Sulfoxide Reductase A. Fort Belvoir, VA: Defense Technical Information Center, May 2008. http://dx.doi.org/10.21236/ada485775.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Sengupta-Gopalan, Champa, Shmuel Galili, and Rachel Amir. Improving Methionine Content in Transgenic Forage Legumes. United States Department of Agriculture, February 2001. http://dx.doi.org/10.32747/2001.7580671.bard.

Full text
Abstract:
Leguminous forage crops are high in proteins but deficient in S- amino acids. It has been shown that both wool quality and milk production can be limited by the post-ruminal supply of sulfur-containing amino acids. Efforts to use conventional plant breeding and cell selection techniques to increase the S-amino acid content of alfalfa have met with little success. With the objective to increase the S-amino acid content of forage legumes, the goal of this project was to co- express the methionine rich zein genes from corn along with a gene for a key enzyme in methionine biosynthesis, aspartate kinase(AK). The zeins are seed storage proteins from corn and are groupec into four distinct classes based on their amino acid sequence homologies. The b-zein (15kd) and the 6zein (10kD and 18kD) have proportionately high levels of methionine (10%, 22% and 28%, respectively). Initial studies from our lab had shown that while the 15kD zein accumulated to high levels in vegetative tissues of transgenic tobacco the l0kD zein did not. However, co-expression of the 10kD zein with the 15kD zein genes in tobacco showed stabilization of the 10kD zein and the co-localization of the 10kD and 15kD zein proteins in unique ER derived protein bodies. AK is the key enzyme for producing carbon skeletons for all amino acids of the aspartate family including methionine. It is, however, regulated by end-product feedback inhibition. The specific objectives of this proposal were: i. to co-express the 15kD zein with the 10/18kD zein genes in alfalfa in order to enhance the level of accumulation of the 10/18kD zein; ii. to increase methionine pools by expressing a feedback insensitive AK gene in transformants co-expressing the 15kD and 10/18kD zein genes. The Israeli partners were successful in expressing the AK gene in alfalfa which resulted in an increase in free and bound threonine but not in methionine (Galili et al., 2000). Since our target was to increase methionine pools, we changed our second objective to replace the AK gene with the gene for cystathionine gamma synthase (CGS) in the co-expression studies. The first methionine specific reaction is catalyzed by CGS. An additional objective was to develop a transformation system for Berseem clover, and to introduce the appropriate gene constructs into it with the goal of improving their methionine content. Genes for the 15kD zein along with the genes for either the 10kD or 18kD zein have been introduced into the same alfalfa plant both by sexual crosses and by re-transformation. Analysis of these zein co-expressors have shown that both the IOkD and 18kD zein levels go up 5 to 10 fold when co-expressed with the 15kD zein (Bagga et al., MS in preparation). Incubation of the leaves of transgenic alfalfa co-expressing the 15kD and 10kD zein genes, in the rumen of cows have shown that the zein proteins are stable in the rumen. To increase the level of zein accumulation in transgenic alfalfa different promoters have been used to drive the zein genes in alfalfa and we have concluded that the CaMV 35S promoter is superior to the other strong leaf -specific promoters. By feeding callus tissue of alfalfa plants co-expressing the 15kD and 10kD zein genes with methionine and its precursors, we have shown that the zein levels could be significantly enhanced by increasing the methionine pools. We have now introduced the CGS gene (from Arabidopsis; kindly provided to us by Dr. Leustek), into the 15kD zein transformants and experiments are in progress to check if the expression of the CGS gene indeed increases the level of zein accumulation in alfalfa. We were not successful in developing a transformation protocol for Berseem clover.
APA, Harvard, Vancouver, ISO, and other styles
3

Harrison, Roger G. New Enzyme Prodrug and Methionine-Depletion Combination Therapy of Breast Cancer Designed for Effective Delivery to the Tumor. Fort Belvoir, VA: Defense Technical Information Center, October 2010. http://dx.doi.org/10.21236/ada535378.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Harrison, Roger G. New Enzyme Prodrug and Methionine-Depletion Combination Therapy of Breast Cancer Designed for Effective Delivery to the Tumor. Fort Belvoir, VA: Defense Technical Information Center, October 2009. http://dx.doi.org/10.21236/ada541307.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Harrison, Roger G. New Enzyme Prodrug and Methionine-Depletion Combination Therapy of Breast Cancer Designed for Effective Delivery to the Tumor. Fort Belvoir, VA: Defense Technical Information Center, October 2012. http://dx.doi.org/10.21236/ada574387.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Harrison, Roger. New Enzyme Prodrug and Methionine-Depletion Combination Therapy of Breast Cancer Designed for Effective Delivery to the Tumor. Fort Belvoir, VA: Defense Technical Information Center, October 2011. http://dx.doi.org/10.21236/ada555297.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Amir, Rachel, David J. Oliver, Gad Galili, and Jacline V. Shanks. The Role of Cysteine Partitioning into Glutathione and Methionine Synthesis During Normal and Stress Conditions. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7699850.bard.

Full text
Abstract:
The objective of this research is to study the nature of the competition for cysteine (Cys), the first organic sulfur-containing compound, between its two main metabolites, glutathione (GSH) and methionine (Met). GSH plays a central role in protecting plants during various stresses, while Met, an essential amino acid, regulates essential processes and metabolites in plant cells through its metabolite S-adenosyl-Met. Our results, which are based on flux analysis and measurements of Met- metabolites, show that the flux towards Met synthesis is high during non-stress conditions, however the flux is significantly reduced under stress conditions, when there is high synthesis of GSH. Under oxidative stress the expression level of the regulatory enzyme of Met synthesis, cystathionine g-synthase (CGS) was reduced. By using three different systems, we have found that that GSH down regulates the expression level of CGS, thus reducing Met synthesis. We have found that this regulation occurs at the post-transcriptional level, and further studies have shown that it occurs at post-translationaly. To reveal how oxidative stress affects the flux towards Met and GSH, flux analysis was performed. We have found that the level of Met is significantly reduced, while the level of glutathione significantly increases during stress. Under stress conditions most of the glutathione is converted from GSH to GSSG (the oxidised form of glutathione). These results suggest that under normal growth conditions, Cys is channelled towards both pathways to support GSH accumulation and the synthesis of growth-essential Met metabolites. However, during oxidative stress, when a high level of GSH is required to protect the plants, the levels of GSH increase while those of CGS are reduced. This reduction leaves more Cys available for GSH synthesis under stress conditions. In addition we have also studied the effects of high GSH level on the transcriptome profile. The analysis revealed that GSH affects the expression level of many major genes coding to enzymes or proteins associated with photosynthesis, starch degradation, hormone metabolism (especially genes associated with jasmonate), biotic stress (especially genes associated with PR-proteins), cytochrome P450 genes, regulation of transcription and signaling (especially genes associated with receptor kinases and calcium). These results suggest that indeed GSH levels affect different pathways and metabolites in plants.
APA, Harvard, Vancouver, ISO, and other styles
8

Jander, Georg, Gad Galili, and Yair Shachar-Hill. Genetic, Genomic and Biochemical Analysis of Arabidopsis Threonine Aldolase and Associated Molecular and Metabolic Networks. United States Department of Agriculture, January 2010. http://dx.doi.org/10.32747/2010.7696546.bard.

Full text
Abstract:
Since the amino acids threonine and isoleucine can be limiting in mammalian diet and there is interest in increasing their abundance in certain crop plants. To meet this need, a BARD proposal was written with two main research objectives: (i) investigate new avenues for manipulating threonine and isoleucine content in plants and (ii) study the role of threonine aldolase in plant metabolism. Research conducted to meet these goals included analysis of the sub-cellular localization of threonine aldolase in the plant, analysis of metabolic flux in developing embryos, over- and under-expression of Arabidopsis threonine aldolases, and transcriptional and metabolic analysis of perturbations resulting from altered threonine aldolase expression. Additionally, the broader metabolic effects of increasing lysine biosynthesis were investigated. An interesting observation that came up in the course of the project is that threonine aldolase activity affects methionine gamma-lyase in Arabidopsis. Further research showed that threonine deaminase and methionine gamma-lyase both contribute to isoleucine biosynthesis in plants. Therefore, isoleucine content can be altered by manipulating the expression of either or both of these enzymes. Additionally, both enzymes contribute to the up to 100-fold increase in isoleucine that is observed in drought-stressed Arabidopsis. Toward the end of the project it was discovered that through different projects, both groups had been able to independently up-regulate phenylalanine accumulation by different mechanisms. The Galili lab transformed Arabidopsis with a feedbackinsensitive bacterial enzyme and the Jander lab found a feedback insensitive mutation in Arabidopsis arogenate dehydratase. Exchange of the respective plant lines has allowed a comparative analysis of the different methods for increasing phenylalanine content and the creation of double mutants. The research that was conducted as part of this BARD project has led to new insights into plant amino acid metabolism. Additionally, new approaches that were found to increase the accumulation of threonine, isoleucine, and phenylalanine in plants have potential practical applications. Increased threonine and isoleucine levels can increase the nutritional value of crop plants. Elevated isoleucine accumulation may increase the osmotic stress tolerance of plants. Up-regulation of phenylalanine biosynthesis can be used to increase the production of downstream higher-value plant metabolites of biofuel feed stocks.
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'Methionase enzyme' for particular source types:
Journal articles Dissertations / Theses
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography