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Paul, Anju, Archita Mishra, Avadhesha Surolia i Mamannamana Vijayan. "Structural studies on M. tuberculosis argininosuccinate lyase and its liganded complex: Insights into catalytic mechanism". IUBMB Life 71, nr 5 (7.01.2019): 643–52. http://dx.doi.org/10.1002/iub.2000.
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Chen, Xiaobo, Jiayue Chen, Wei Zhang, Huiying Wang, Xiang Liu, Weihong Zhou, Haitao Yang i Zihe Rao. "Crystal structure and biochemical study on argininosuccinate lyase from Mycobacterium tuberculosis". Biochemical and Biophysical Research Communications 510, nr 1 (luty 2019): 116–21. http://dx.doi.org/10.1016/j.bbrc.2019.01.061.
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Salapatek, Anne Marie F., Yu-Fang Wang, Yu-Kang Mao, Masataka Mori i Edwin E. Daniel. "Myogenic NOS in canine lower esophageal sphincter: enzyme activation, substrate recycling, and product actions". American Journal of Physiology-Cell Physiology 274, nr 4 (1.04.1998): C1145—C1157. http://dx.doi.org/10.1152/ajpcell.1998.274.4.c1145.
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Depolarization elicited outward K+ currents from canine lower esophageal sphincter (LES) muscle cells, primarily through iberiotoxin (IbTX)- and tetraethylammonium-sensitive Ca2+-dependent K+ channels. Current magnitudes varied with pipette Ca2+concentration (EC50 = 108.5 nM). N G-nitro-l-arginine (l-NNA, 10−4 M), IbTX (10−8 M), or buffering intracellular Ca2+ to 8 nM decreased outward currents >80%. Sodium nitroprusside (NaNP, 10−4 M) restoredl-NNA-inhibited or low intracellular Ca2+ concentration (not IbTX)-inhibited currents.l-NNA or IbTX application depolarized LES cells from −43 to −35 mV. NaNP restored the membrane potential to −46 mV afterl-NNA but not after IbTX application. Nifedipine (30 μM) reduced outward currents and abolished or reduced l-NNA or NaNP effects, respectively. Immunocytochemistry revealed the presence of both argininosuccinate synthetase and argininosuccinate lyase in LES muscle cells. l-Citrulline, likel-arginine, reversedl-NNA inhibition of outward currents; only l-arginine reversed inhibition of outward currents by an antibody to argininosuccinate synthetase. Therefore, endogenous nitric oxide production, activated by Ca2+entrance involving l-type Ca2+ channels, may continuously enhance outward currents to modulate LES muscle cell membrane potential and excitability.
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Chung, Sai-Fung, Chi-Fai Kim, Ho-Yin Chow, Hiu-Chi Chong, Suet-Ying Tam, Yun-Chung Leung i Wai-Hung Lo. "Recombinant Bacillus caldovelox Arginase Mutant (BCA-M) Induces Apoptosis, Autophagy, Cell Cycle Arrest and Growth Inhibition in Human Cervical Cancer Cells". International Journal of Molecular Sciences 21, nr 20 (9.10.2020): 7445. http://dx.doi.org/10.3390/ijms21207445.
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With our recent success in developing a recombinant human arginase drug against broad-spectrum cancer cell lines, we have explored the potential of a recombinant Bacillus caldovelox arginase mutant (BCA-M) for human cervical cancer treatment. Our studies demonstrated that BCA-M significantly inhibited the growth of human cervical cancer cells in vitro regardless of argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) expression. Drug susceptibilities correlate well with the expressions of major urea cycle genes and completeness of L-arginine regeneration pathways. With the expressions of ASS and ASL genes conferring resistance to L-arginine deiminase (ADI) which is undergoing Phase III clinical trial, BCA-M offers the advantage of a broader spectrum of susceptible cancer cells. Mechanistic studies showed that BCA-M inhibited the growth of human cervical cancer cells by inducing apoptosis and cell cycle arrest at S and/or G2/M phases. Our results also displayed that autophagy served as a protective mechanism, while the growth inhibitory effects of BCA-M could be enhanced synergistically by its combination to the autophagy inhibitor, chloroquine (CQ), on human cervical cancer cells.
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Paul, A., A. Mishra, A. Surolia i M. Vijayan. "Cloning, expression, purification, crystallization and preliminary X-ray studies of argininosuccinate lyase (Rv1659) fromMycobacterium tuberculosis". Acta Crystallographica Section F Structural Biology and Crystallization Communications 69, nr 12 (29.11.2013): 1422–24. http://dx.doi.org/10.1107/s1744309113031138.
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Lee, H. J., S. H. Chiou i G. G. Chang. "Inactivation of the endogenous argininosuccinate lyase activity of duck δ-crystallin by modification of an essential histidine residue with diethyl pyrocarbonate". Biochemical Journal 293, nr 2 (15.07.1993): 537–44. http://dx.doi.org/10.1042/bj2930537.
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The argininosuccinate lyase activity of duck delta-crystallin was inactivated by diethyl pyrocarbonate at 0 degrees C and pH 7.5. The inactivation followed pseudo-first-order kinetics after appropriate correction for the decomposition of the reagent during the modification period. The plot of the observed pseudo-first-order rate constant versus diethyl pyrocarbonate concentration in the range of 0.17-1.7 mM was linear and went through the origin with a second-order rate constant of 1.45 +/- 0.1 M-1.s-1. The double-logarithmic plot was also linear, with slope of 1.13, which suggested a 1:1 stoichiometry for the reaction between diethyl pyrocarbonate and delta-crystallin. L-Arginine, L-norvaline or L-citrulline protected the argininosuccinate lyase activity of delta-crystallin from diethyl pyrocarbonate inactivation. The dissociation constants for the delta-crystallin-L-arginine and delta-crystallin-L-citrulline binary complexes, determined by the protection experiments, were 4.2 +/- 0.2 and 0.12 +/- 0.04 mM respectively. Fumarate alone had no protective effect. However, fumarate plus L-arginine gave synergistic protection with a ligand binding interacting factor of 0.12 +/- 0.02. The double-protection data conformed to a random Uni Bi kinetic mechanism. Fluorescence-quenching studies indicated that the modified delta-crystallin had minimum, if any, conformational changes as compared with the native delta-crystallin. Inactivation of the enzyme activity was accompanied by an increasing absorbance at 240 nm of the protein. The absorption near 280 nm did not change. Treatment of the modified protein with hydroxylamine regenerated the enzyme activity to the original level. These results strongly indicated the modification of an essential histidine residue. Calculation from the 240 nm absorption changes indicated that only one histidine residue per subunit was modified by the reagent. This super-active histidine residue has a pKa value of approximately 6.8 and acts as a general acid-base catalyst in the enzyme reaction mechanism. Our experimental data are compatible with an E1cB mechanism [Raushel (1984) Arch. Biochem. Biophys. 232, 520-525] for the argininosuccinate lyase with the essential histidine residue close to the arginine-binding domain of delta-crystallin. L-Citrulline, after binding to this domain, might form an extra hydrogen bond with the essential histidine residue.
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Höner Zu Bentrup, Kerstin, Andras Miczak, Dana L. Swenson i David G. Russell. "Characterization of Activity and Expression of Isocitrate Lyase in Mycobacterium avium andMycobacterium tuberculosis". Journal of Bacteriology 181, nr 23 (1.12.1999): 7161–67. http://dx.doi.org/10.1128/jb.181.23.7161-7167.1999.
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ABSTRACT Analysis by two-dimensional gel electrophoresis revealed thatMycobacterium avium expresses several proteins unique to an intracellular infection. One abundant protein with an apparent molecular mass of 50 kDa was isolated, and the N-terminal sequence was determined. It matches a sequence in the M. tuberculosisdatabase (Sanger) with similarity to the enzyme isocitrate lyase of both Corynebacterium glutamicum and Rhodococcus fascians. Only marginal similarity was observed between this open reading frame (ORF) (termed icl) and a second distinct ORF (named aceA) which exhibits a low similarity to other isocitrate lyases. Both ORFs can be found as distinct genes in the various mycobacterial databases recently published. Isocitrate lyase is a key enzyme in the glyoxylate cycle and is essential as an anapleurotic enzyme for growth on acetate and certain fatty acids as carbon source. In this study we express and purify Icl, as well as AceA proteins, and show that both exhibit isocitrate lyase activity. Various known inhibitors for isocitrate lyase were effective. Furthermore, we present evidence that in both M. avium and M. tuberculosis the production and activity of the isocitrate lyase is enhanced under minimal growth conditions when supplemented with acetate or palmitate.
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Mishra, Archita, i Avadhesha Surolia. "Biochemical characterization of argininosuccinate lyase fromM. tuberculosis: significance of a c-terminal cysteine in catalysis and thermal stability". IUBMB Life 69, nr 11 (16.10.2017): 896–907. http://dx.doi.org/10.1002/iub.1683.
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Duan, Changyuan, Qihua Jiang, Xue Jiang, Hongwei Zeng, Qiaomin Wu, Yang Yu i Xiaolan Yang. "Discovery of a Novel Inhibitor Structure of Mycobacterium tuberculosis Isocitrate Lyase". Molecules 27, nr 8 (11.04.2022): 2447. http://dx.doi.org/10.3390/molecules27082447.
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Tuberculosis remains a global threat to public health, and dormant Mycobacterium tuberculosis leads to long-term medication that is harmful to the human body. M. tuberculosis isocitrate lyase (MtICL), which is absent in host cells, is a key rate-limiting enzyme of the glyoxylic acid cycle and is essential for the survival of dormant M. tuberculosis. The aim of this study was to evaluate natural compounds as potential MtICL inhibitors through docking and experimental verification. Screening of the TCMSP database library was done using Discovery Studio 2019 for molecular docking and interaction analysis, with the putative inhibitors of MtICL, 3-BP, and IA as reference ligands. Daphnetin (MOL005118), with a docking score of 94.8 and -CDOCKER interaction energy of 56 kcal/mol, was selected and verified on MtICL in vitro and M. smegmatis; daphnetin gave an IC50 of 4.34 μg/mL for the MtICL enzyme and an MIC value of 128 μg/mL against M. smegmatis, showing enhanced potential in comparison with 3-BP and IA. The interactions and essential amino acid residues of the protein were analyzed. In summary, natural daphnetin may be a promising new skeleton for the design of inhibitors of MtICL to combat dormant M. tuberculosis.
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Lee, Yie-Vern, Habibah A. Wahab i Yee Siew Choong. "Potential Inhibitors for Isocitrate Lyase ofMycobacterium tuberculosisand Non-M. tuberculosis: A Summary". BioMed Research International 2015 (2015): 1–20. http://dx.doi.org/10.1155/2015/895453.
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Isocitrate lyase (ICL) is the first enzyme involved in glyoxylate cycle. Many plants and microorganisms are relying on glyoxylate cycle enzymes to survive upon downregulation of tricarboxylic acid cycle (TCA cycle), especiallyMycobacterium tuberculosis(MTB). In fact, ICL is a potential drug target for MTB in dormancy. With the urge for new antitubercular drug to overcome tuberculosis treat such as multidrug resistant strain and HIV-coinfection, the pace of drug discovery has to be increased. There are many approaches to discovering potential inhibitor for MTB ICL and we hereby review the updated list of them. The potential inhibitors can be either a natural compound or synthetic compound. Moreover, these compounds are not necessary to be discovered only from MTB ICL, as it can also be discovered by a non-MTB ICL. Our review is categorized into four sections, namely, (a) MTB ICL with natural compounds; (b) MTB ICL with synthetic compounds; (c) non-MTB ICL with natural compounds; and (d) non-MTB ICL with synthetic compounds. Each of the approaches is capable of overcoming different challenges of inhibitor discovery. We hope that this paper will benefit the discovery of better inhibitor for ICL.
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Gouzy, Alexandre, Claire Healy, Katherine A. Black, Kyu Y. Rhee i Sabine Ehrt. "Growth of Mycobacterium tuberculosis at acidic pH depends on lipid assimilation and is accompanied by reduced GAPDH activity". Proceedings of the National Academy of Sciences 118, nr 32 (2.08.2021): e2024571118. http://dx.doi.org/10.1073/pnas.2024571118.
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Acidic pH arrests the growth of Mycobacterium tuberculosis in vitro (pH < 5.8) and is thought to significantly contribute to the ability of macrophages to control M. tuberculosis replication. However, this pathogen has been shown to survive and even slowly replicate within macrophage phagolysosomes (pH 4.5 to 5) [M. S. Gomes et al., Infect. Immun. 67, 3199–3206 (1999)] [S. Levitte et al., Cell Host Microbe 20, 250–258 (2016)]. Here, we demonstrate that M. tuberculosis can grow at acidic pH, as low as pH 4.5, in the presence of host-relevant lipids. We show that lack of phosphoenolpyruvate carboxykinase and isocitrate lyase, two enzymes necessary for lipid assimilation, is cidal to M. tuberculosis in the presence of oleic acid at acidic pH. Metabolomic analysis revealed that M. tuberculosis responds to acidic pH by altering its metabolism to preferentially assimilate lipids such as oleic acid over carbohydrates such as glycerol. We show that the activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is impaired in acid-exposed M. tuberculosis likely contributing to a reduction in glycolytic flux. The generation of endogenous reactive oxygen species at acidic pH is consistent with the inhibition of GAPDH, an enzyme well-known to be sensitive to oxidation. This work shows that M. tuberculosis alters its carbon diet in response to pH and provides a greater understanding of the physiology of this pathogen during acid stress.
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Micklinghoff, Julia C., Katrin J. Breitinger, Mascha Schmidt, Robert Geffers, Bernhard J. Eikmanns i Franz-Christoph Bange. "Role of the Transcriptional Regulator RamB (Rv0465c) in the Control of the Glyoxylate Cycle in Mycobacterium tuberculosis". Journal of Bacteriology 191, nr 23 (18.09.2009): 7260–69. http://dx.doi.org/10.1128/jb.01009-09.
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ABSTRACT Mycobacterium tuberculosis generally is assumed to depend on lipids as a major carbon and energy source when persisting within the host. The utilization of fatty acids requires a functional glyoxylate cycle with the key enzymes isocitrate lyase (Icl) and malate synthase. The open reading frame Rv0465c of M. tuberculosis H37Rv encodes a protein with significant sequence similarity to the transcriptional regulator RamB, which in Corynebacterium glutamicum controls the expression of several genes involved in acetate metabolism, i.e., those encoding enzymes of acetate activation and the glyoxylate cycle. We show here that the M. tuberculosis Rv0465c protein can functionally complement RamB in C. glutamicum and that it binds to the promoter regions of M. tuberculosis icl1 and Rv0465c. Construction and subsequent transcriptional and enzymatic analysis of a defined Rv0465c deletion mutant in M. tuberculosis revealed that the Rv0465c protein, now designated RamB, represses icl1 expression during growth with glucose and negatively autoregulates the expression of its own operon. Whole-genome microarray analysis of the M. tuberculosis ramB (ramBMT ) mutant and the wild type furthermore showed that apart from icl1 and the ramBMT operon, the expression of all other M. tuberculosis genes involved in acetate metabolism remain unchanged in the mutant. Thus, RamBMT has a more specific regulatory function as RamB from C. glutamicum and is confined to expression control of icl1 and the ramBMT operon.
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Chanda, Anesha, Sanjib Kalita, Awdhesh Kumar Mishra, Liza Changkakoti, Janayita Biswa Sarma, Kunal Biswas, Debashree Kakati i in. "Identification of Concomitant Inhibitors against Glutamine Synthetase and Isocitrate Lyase in Mycobacterium tuberculosis from Natural Sources". BioMed Research International 2022 (3.10.2022): 1–14. http://dx.doi.org/10.1155/2022/4661491.
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Tuberculosis (T.B.) is a disease that occurs due to infection by the bacterium, Mycobacterium tuberculosis (Mtb), which is responsible for millions of deaths every year. Due to the emergence of multidrug and extensive drug-resistant Mtb strains, there is an urgent need to develop more powerful drugs for inclusion in the current tuberculosis treatment regime. In this study, 1778 molecules from four medicinal plants, Azadirachta indica, Camellia sinensis, Adhatoda vasica, and Ginkgo biloba, were selected and docked against two chosen drug targets, namely, Glutamine Synthetase (G.S.) and Isocitrate Lyase (I.C.L.). Molecular Docking was performed using the Glide module of the Schrӧdinger suite to identify the best-performing ligands; the complexes formed by the best-performing ligands were further investigated for their binding stability via Molecular Dynamics Simulation of 100 ns. The present study suggests that Azadiradione from Azadirachta indica possesses the potential to inhibit Glutamine Synthetase and Isocitrate Lyase of M. tuberculosis concomitantly. The excellent docking score of the ligand and the stability of receptor-ligand complexes, coupled with the complete pharmacokinetic profile of Azadiradione, support the proposal of the small molecule, Azadiradione as a novel antitubercular agent. Further, wet lab analysis of Azadiradione may lead to the possible discovery of a novel antitubercular drug.
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Savvi, Suzana, Digby F. Warner, Bavesh D. Kana, John D. McKinney, Valerie Mizrahi i Stephanie S. Dawes. "Functional Characterization of a Vitamin B12-Dependent Methylmalonyl Pathway in Mycobacterium tuberculosis: Implications for Propionate Metabolism during Growth on Fatty Acids". Journal of Bacteriology 190, nr 11 (28.03.2008): 3886–95. http://dx.doi.org/10.1128/jb.01767-07.
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ABSTRACT Mycobacterium tuberculosis is predicted to subsist on alternative carbon sources during persistence within the human host. Catabolism of odd- and branched-chain fatty acids, branched-chain amino acids, and cholesterol generates propionyl-coenzyme A (CoA) as a terminal, three-carbon (C3) product. Propionate constitutes a key precursor in lipid biosynthesis but is toxic if accumulated, potentially implicating its metabolism in M. tuberculosis pathogenesis. In addition to the well-characterized methylcitrate cycle, the M. tuberculosis genome contains a complete methylmalonyl pathway, including a mutAB-encoded methylmalonyl-CoA mutase (MCM) that requires a vitamin B12-derived cofactor for activity. Here, we demonstrate the ability of M. tuberculosis to utilize propionate as the sole carbon source in the absence of a functional methylcitrate cycle, provided that vitamin B12 is supplied exogenously. We show that this ability is dependent on mutAB and, furthermore, that an active methylmalonyl pathway allows the bypass of the glyoxylate cycle during growth on propionate in vitro. Importantly, although the glyoxylate and methylcitrate cycles supported robust growth of M. tuberculosis on the C17 fatty acid heptadecanoate, growth on valerate (C5) was significantly enhanced through vitamin B12 supplementation. Moreover, both wild-type and methylcitrate cycle mutant strains grew on B12-supplemented valerate in the presence of 3-nitropropionate, an inhibitor of the glyoxylate cycle enzyme isocitrate lyase, indicating an anaplerotic role for the methylmalonyl pathway. The demonstrated functionality of MCM reinforces the potential relevance of vitamin B12 to mycobacterial pathogenesis and suggests that vitamin B12 availability in vivo might resolve the paradoxical dispensability of the methylcitrate cycle for the growth and persistence of M. tuberculosis in mice.
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Harrison, Anthony J., Minmin Yu, Therés Gårdenborg, Martin Middleditch, Rochelle J. Ramsay, Edward N. Baker i J. Shaun Lott. "The Structure of MbtI from Mycobacterium tuberculosis, the First Enzyme in the Biosynthesis of the Siderophore Mycobactin, Reveals It To Be a Salicylate Synthase". Journal of Bacteriology 188, nr 17 (1.09.2006): 6081–91. http://dx.doi.org/10.1128/jb.00338-06.
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ABSTRACT The ability to acquire iron from the extracellular environment is a key determinant of pathogenicity in mycobacteria. Mycobacterium tuberculosis acquires iron exclusively via the siderophore mycobactin T, the biosynthesis of which depends on the production of salicylate from chorismate. Salicylate production in other bacteria is either a two-step process involving an isochorismate synthase (chorismate isomerase) and a pyruvate lyase, as observed for Pseudomonas aeruginosa, or a single-step conversion catalyzed by a salicylate synthase, as with Yersinia enterocolitica. Here we present the structure of the enzyme MbtI (Rv2386c) from M. tuberculosis, solved by multiwavelength anomalous diffraction at a resolution of 1.8 Å, and biochemical evidence that it is the salicylate synthase necessary for mycobactin biosynthesis. The enzyme is critically dependent on Mg2+ for activity and produces salicylate via an isochorismate intermediate. MbtI is structurally similar to salicylate synthase (Irp9) from Y. enterocolitica and the large subunit of anthranilate synthase (TrpE) and shares the overall architecture of other chorismate-utilizing enzymes, such as the related aminodeoxychorismate synthase PabB. Like Irp9, but unlike TrpE or PabB, MbtI is neither regulated by nor structurally stabilized by bound tryptophan. The structure of MbtI is the starting point for the design of inhibitors of siderophore biosynthesis, which may make useful lead compounds for the production of new antituberculosis drugs, given the strong dependence of pathogenesis on iron acquisition in M. tuberculosis.
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Walsh, P. "Subcellular localization and biochemical properties of the enzymes of carbamoyl phosphate and urea synthesis in the batrachoidid fishes Opsanus beta, Opsanus tau and Porichthys notatus". Journal of Experimental Biology 198, nr 3 (1.03.1995): 755–66. http://dx.doi.org/10.1242/jeb.198.3.755.
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The subcellular localization and biochemical properties of the enzymes of carbamoyl phosphate and urea synthesis were examined in three representatives of fishes of the family Batrachoididae, the gulf toadfish (Opsanus beta), the oyster toadfish (Opsanus tau) and the plainfin midshipman (Porichthys notatus). The primary objective of the study was to compare the biochemical characteristics of these fishes, which represent a range between ammoniotelism and ureotelism (O. beta being facultatively ureotelic), with previous patterns observed for an ammoniotelic teleost (Micropterus salmoides, the largemouth bass) and an obligate ureogenic elasmobranch (Squalus acanthias, the dogfish shark). The present study documents the expression of mitochondrial carbamoyl phosphate synthetase (CPSase) III and cytosolic CPSase II (and its associated enzymes of pyrimidine synthesis, dihydro-orotase and aspartate carbamoyltransferase) in the livers of all three batrachoidid species. Both mitochondrial and cytosolic activities of arginase were present in the livers of all three species, as were cytosolic glutamine synthetase and argininosuccinate synthetase and lyase. However, O. beta also showed mitochondrial glutamine synthetase activity and higher total hepatic levels of glutamine synthetase than either O. tau or P. notatus. Taken together, these observations confirm that the arrangement of these enzymes in the batrachoidid fishes has greater similarity to that of M. salmoides than to that of S. acanthias. However, differences within the family appear to coincide with the different nitrogen excretion strategies. O. tau and P. notatus are primarily ammoniotelic and most closely resemble the ammoniotelic M. salmoides, whereas ureotelism in O. beta is correlated with the presence of a mitochondrial glutamine synthetase and the ability to induce higher total glutamine synthetase activities than O. tau or P. notatus. Additionally, isolated mitochondria from O. beta were able to generate citrulline from glutamine, whereas those from O. tau were not. Also in contrast to S. acanthias, glutamine synthetase activities in the mitochondria of O. beta are consistently lower than those of CPSase III. This and other kinetic observations lend support to the hypothesis that glutamine synthetase may be an important regulatory control point in determining rates of ureogenesis in O. beta.
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Wang, Xiao-Ming, Changlong Lu, Karine Soetaert, Catherine S'Heeren, Priska Peirs, Marie-Antoinette Lanéelle, Philippe Lefèvre i in. "Biochemical and immunological characterization of a cpn60.1 knockout mutant of Mycobacterium bovis BCG". Microbiology 157, nr 4 (1.04.2011): 1205–19. http://dx.doi.org/10.1099/mic.0.045120-0.
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Pathogenic mycobacteria possess two homologous chaperones encoded by cpn60.1 and cpn60.2. Cpn60.2 is essential for survival, providing the basic chaperone function, while Cpn60.1 is not. In the present study, we show that inactivation of the Mycobacterium bovis BCG cpn60.1 (Mb3451c) gene does not significantly affect bacterial growth in 7H9 broth, but that this knockout mutant (Δcpn60.1) forms smaller colonies on solid 7H11 medium than the parental and complemented strains. When growing on Sauton medium, the Δcpn60.1 mutant exhibits a thinner surface pellicle and is associated with higher culture filtrate protein content and, coincidentally, with less protein in its outermost cell envelope in comparison with the parental and complemented strains. Interestingly, in this culture condition, the Δcpn60.1 mutant is devoid of phthiocerol dimycocerosates, and its mycolates are two carbon atoms longer than those of the wild-type, a phenotype that is fully reversed by complementation. In addition, Δcpn60.1 bacteria are more sensitive to stress induced by H2O2 but not by SDS, high temperature or acidic pH. Taken together, these data indicate that the cell wall of the Δcpn60.1 mutant is impaired. Analysis by 2D gel electrophoresis and MS reveals the upregulation of a few proteins such as FadA2 and isocitrate lyase in the cell extract of the mutant, whereas more profound differences are found in the composition of the mycobacterial culture filtrate, e.g. the well-known Hsp65 chaperonin Cpn60.2 is particularly abundant and increases about 200-fold in the filtrate of the Δcpn60.1 mutant. In mice, the Δcpn60.1 mutant is less persistent in lungs and, to a lesser extent, in spleen, but it induces a comparable mycobacteria-specific gamma interferon production and protection against Mycobacterium tuberculosis H37Rv challenge as do the parental and complemented BCG strains. Thus, by inactivating the cpn60.1 gene in M. bovis BCG we show that Cpn60.1 is necessary for the integrity of the bacterial cell wall, is involved in resistance to H2O2-induced stress but is not essential for its vaccine potential.
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Ibeji, Collins U., Nor Amirah Mohd Salleh, Jia Siang Sum, Angela Chiew Wen Ch’ng, Theam Soon Lim i Yee Siew Choong. "Demystifying the catalytic pathway of Mycobacterium tuberculosis isocitrate lyase". Scientific Reports 10, nr 1 (3.11.2020). http://dx.doi.org/10.1038/s41598-020-75799-8.
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Abstract Pulmonary tuberculosis, caused by Mycobacterium tuberculosis, is one of the most persistent diseases leading to death in humans. As one of the key targets during the latent/dormant stage of M. tuberculosis, isocitrate lyase (ICL) has been a subject of interest for new tuberculosis therapeutics. In this work, the cleavage of the isocitrate by M. tuberculosis ICL was studied using quantum mechanics/molecular mechanics method at M06-2X/6-31+G(d,p): AMBER level of theory. The electronic embedding approach was applied to provide a better depiction of electrostatic interactions between MM and QM regions. Two possible pathways (pathway I that involves Asp108 and pathway II that involves Glu182) that could lead to the metabolism of isocitrate was studied in this study. The results suggested that the core residues involved in isocitrate catalytic cleavage mechanism are Asp108, Cys191 and Arg228. A water molecule bonded to Mg2+ acts as the catalytic base for the deprotonation of isocitrate C(2)–OH group, while Cys191 acts as the catalytic acid. Our observation suggests that the shuttle proton from isocitrate hydroxyl group C(2) atom is favourably transferred to Asp108 instead of Glu182 with a lower activation energy of 6.2 kcal/mol. Natural bond analysis also demonstrated that pathway I involving the transfer of proton to Asp108 has a higher intermolecular interaction and charge transfer that were associated with higher stabilization energy. The QM/MM transition state stepwise catalytic mechanism of ICL agrees with the in vitro enzymatic assay whereby Asp108Ala and Cys191Ser ICL mutants lost their isocitrate cleavage activities.
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Ko, Eon-Min, Ju-Yeon Kim, Sujin Lee, Suhkmann Kim, Jihwan Hwang i Jeong-Il Oh. "Regulation of the icl1 gene encoding the major isocitrate lyase in Mycobacterium smegmatis". Journal of Bacteriology, 13.09.2021. http://dx.doi.org/10.1128/jb.00402-21.
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Mycobacterium smegmatis has two isocitrate lyase (ICL) isozymes (MSMEG_0911 and MSMEG_3706). We demonstrated that ICL1 (MSMEG_0911) is the predominantly expressed ICL in M. smegmatis and plays a major role in growth on acetate or fatty acid as the sole carbon and energy source. Expression of the icl1 gene in M. smegmatis was demonstrated to be strongly upregulated during growth on acetate relative to that in M. smegmatis grown on glucose. Expression of icl1 was shown to be positively regulated by the RamB activator, and three RamB-binding sites (RamBS1, RamBS2, and RamBS3) were identified in the upstream region of icl1 using DNase I footprinting analysis. Succinyl-CoA was shown to increase the binding affinity of RamB to its binding sites and enable RamB to bind to RamBS2 that is the most important site for RamB-mediated induction of icl1 expression. These results suggest that succinyl-CoA serves as a coinducer molecule for RamB. Our study also showed that cAMP receptor protein (Crp1: MSMEG_6189) represses icl1 expression in M. smegmatis grown in the presence of glucose. Therefore, the strong induction of icl1 expression during growth on acetate as the sole carbon source relative to the weak expression of icl1 during growth on glucose is likely to result from combined effects of RamB-mediated induction of icl1 in the presence of acetate and Crp-mediated repression of icl1 in the presence of glucose. IMPORTANCE Carbon flux through the glyoxylate shunt has been suggested to affect virulence, persistence, and antibiotic resistance of Mycobacterium tuberculosis . Therefore, it is important to understand the precise mechanism underlying the regulation of the icl gene encoding the key enzyme of the glyoxylate shunt. Using Mycobacterium smegmatis , this study revealed the regulation mechanism underlying induction of icl1 expression in M. smegmatis when the glyoxylate shunt is required. The conservation of the cis - and trans -acting regulatory elements related to icl1 regulation in both M. smegmatis and M. tuberculosis implies that the similar regulatory mechanism operates for the regulation of icl1 expression in M. tuberculosis .
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Havis, Spencer, Abiodun Bodunrin, Jonathan Rangel, Rene Zimmerer, Jesse Murphy, Jacob D. Storey, Thinh D. Duong i in. "A Universal Stress Protein That Controls Bacterial Stress Survival in Micrococcus luteus". Journal of Bacteriology 201, nr 24 (23.09.2019). http://dx.doi.org/10.1128/jb.00497-19.
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ABSTRACT Bacteria have remarkable mechanisms to survive severe external stresses, and one of the most enigmatic is the nonreplicative persistent (NRP) state. Practically, NRP bacteria are difficult to treat, and so inhibiting the proteins underlying this survival state may render such bacteria more susceptible to external stresses, including antibiotics. Unfortunately, we know little about the proteins and mechanisms conferring survival through the NRP state. Here, we report that a universal stress protein (Usp) is a primary regulator of bacterial survival through the NRP state in Micrococcus luteus NCTC 2665, a biosafety level 1 (BSL1) mycobacterial relative. Usps are widely conserved, and bacteria, including Mycobacterium tuberculosis, Mycobacterium smegmatis, and Escherichia coli, have multiple paralogs with overlapping functions that have obscured their functional roles. A kanamycin resistance cassette inserted into the M. luteus universal stress protein A 616 gene (ΔuspA616::kan M. luteus) ablates the UspA616 protein and drastically impairs M. luteus survival under even short-term starvation (survival, 83% wild type versus 32% ΔuspA616::kan M. luteus) and hypoxia (survival, 96% wild type versus 48% ΔuspA616::kan M. luteus). We observed no detrimental UspA616 knockout phenotype in logarithmic growth. Proteomics demonstrated statistically significant log-phase upregulation of glyoxylate pathway enzymes isocitrate lyase and malate synthase in ΔuspA616::kan M. luteus. We note that these enzymes and the M. tuberculosis UspA616 homolog (Rv2623) are important in M. tuberculosis virulence and chronic infection, suggesting that Usps are important stress proteins across diverse bacterial species. We propose that UspA616 is a metabolic switch that controls survival by regulating the glyoxylate shunt. IMPORTANCE Bacteria tolerate severe external stresses, including antibiotics, through a nonreplicative persistent (NRP) survival state, yet the proteins regulating this survival state are largely unknown. We show a specific universal stress protein (UspA616) controls the NRP state in Micrococcus luteus. Usps are widely conserved across bacteria, but their biological function(s) has remained elusive. UspA616 inactivation renders M. luteus susceptible to stress: bacteria die instead of adapting through the NRP state. UspA616 regulates malate synthase and isocitrate lyase, glyoxylate pathway enzymes important for chronic Mycobacterium tuberculosis infection. These data show that UspA616 regulates NRP stress survival in M. luteus and suggest a function for homologous proteins in other bacteria. Importantly, inhibitors of UspA616 and homologs may render NRP bacteria more susceptible to stresses, including current antibiotics.
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Puniya, Bhanwar Lal, Deepika Kulshreshtha, Inna Mittal, Ahmed Mobeen i Srinivasan Ramachandran. "Integration of Metabolic Modeling with Gene Co-expression Reveals Transcriptionally Programmed Reactions Explaining Robustness in Mycobacterium tuberculosis". Scientific Reports 6, nr 1 (22.03.2016). http://dx.doi.org/10.1038/srep23440.
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Abstract Robustness of metabolic networks is accomplished by gene regulation, modularity, re-routing of metabolites and plasticity. Here, we probed robustness against perturbations of biochemical reactions of M. tuberculosis in the form of predicting compensatory trends. In order to investigate the transcriptional programming of genes associated with correlated fluxes, we integrated with gene co-expression network. Knock down of the reactions NADH2r and ATPS responsible for producing the hub metabolites, and Central carbon metabolism had the highest proportion of their associated genes under transcriptional co-expression with genes of their flux correlated reactions. Reciprocal gene expression correlations were observed among compensatory routes, fresh activation of alternative routes and in the multi-copy genes of Cysteine synthase and of Phosphate transporter. Knock down of 46 reactions caused the activation of Isocitrate lyase or Malate synthase or both reactions, which are central to the persistent state of M. tuberculosis. A total of 30 new freshly activated routes including Cytochrome c oxidase, Lactate dehydrogenase, and Glycine cleavage system were predicted, which could be responsible for switching into dormant or persistent state. Thus, our integrated approach of exploring transcriptional programming of flux correlated reactions has the potential to unravel features of system architecture conferring robustness.
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Sharma, Shweta, Rupesh Chikhale, Nivedita Shinde, A. M. Khan i Vivek Kumar Gupta. "Targeting dormant phenotype acquired mycobacteria using natural products by exploring its important targets: In vitro and in silico studies". Frontiers in Cellular and Infection Microbiology 13 (24.03.2023). http://dx.doi.org/10.3389/fcimb.2023.1111997.
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The dormant phenotype of Mycobacterium tuberculosis that develops during infection poses a major challenge in disease treatment, since these bacilli show tolerance to front-line drugs. An in vitro hypoxia dormancy model was established, which produced phenotypically dormant Mycobacterium smegmatis after prolonged incubation under conditions of low oxygen, low pH, and nutrient limitation. Bacilli in this model displayed the classical dormancy characters, including loss of acid fastness, altered morphology, and, most importantly, tolerance to front-line drugs. The dormant form of M. smegmatis was treated with drugs and phytomolecules. Three phytomolecules exhibited activity against dormant bacilli, as shown by lack of regrowth in solid and liquid media. Further investigation of dormancy-active hits was carried out using in silico approaches to understand the druggable targets of these phytomolecules in dormant bacilli. For this study, molecular docking, molecular dynamics simulations (MDS), and molecular mechanics-generalized born solvent accessibility (MM-GBSA)-based binding energy (ΔGbind) calculations were performed. Five different targets, namely, isocitrate lyase (ICL), GMP synthase, LuxR, DosR, and serine/threonine protein kinase (STPK), from M. smegmatis and M. tuberculosis were studied in details. DosR and STPK were found to be the common targets in both the species that were more prone to the phytomolecules. The standard DosR inhibitor, HC104A, showed a lower dock score and binding energy of −4.27 and −34.50 kcal/mol, respectively, compared to the natural products under study. The phytomolecule, icariin, showed better docking score (dock score = −5.92 kcal/mol with and binding energy ΔGbind= −52.96 kcal/mol) with DosR compared to known DosR inhibitor, HC104A (dock score = −4.27 kcal/mol and binding energy ΔGbind = −34.50 kcal/mol). Similarly, the known STPK inhibitor MRCT67127 showed a lower dock score and binding energy of −4.25 and −29.43 kcal/mol, respectively, compared to the phytomolecule, icariin (dock score = −5.74 kcal/mol and ΔGbind= −43.41 kcal/mol). These compounds might ultimately lead to new therapeutics or may be useful as adjuvants to the first-line drugs to reduce the lengthy anti-TB therapy in the future.