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Habibi-Khorassani SM, Shahraki M, Talaiefar S. Kinetics and a mechanistic investigation of 2H-thiopyrano [2, 3-b] quinoline-2, 3-dicarboxylates from 2-mercaptoquinoline-3-carbaldehydes, dialkyl acetylenedicarboxylates and triphenylphosphine: Empirical approach. PHOSPHORUS SULFUR 2021. [DOI: 10.1080/10426507.2020.1833330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
| | - Mehdi Shahraki
- Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
| | - Sadegh Talaiefar
- Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
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Sao Emani C, Williams MJ, Wiid IJ, Baker B. The functional interplay of low molecular weight thiols in Mycobacterium tuberculosis. J Biomed Sci 2018; 25:55. [PMID: 30001196 PMCID: PMC6042322 DOI: 10.1186/s12929-018-0458-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/05/2018] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Three low molecular weight thiols are synthesized by Mycobacterium tuberculosis (M.tb), namely ergothioneine (ERG), mycothiol (MSH) and gamma-glutamylcysteine (GGC). They are able to counteract reactive oxygen species (ROS) and/or reactive nitrogen species (RNS). In addition, the production of ERG is elevated in the MSH-deficient M.tb mutant, while the production of MSH is elevated in the ERG-deficient mutants. Furthermore, the production of GGC is elevated in the MSH-deficient mutant and the ERG-deficient mutants. The propensity of one thiol to be elevated in the absence of the other prompted further investigations into their interplay in M.tb. METHODS To achieve that, we generated two M.tb mutants that are unable to produce ERG nor MSH but are able to produce a moderate (ΔegtD-mshA) or significantly high (ΔegtB-mshA) amount of GGC relative to the wild-type strain. In addition, we generated an M.tb mutant that is unable to produce GGC nor MSH but is able to produce a significantly low level of ERG (ΔegtA-mshA) relative to the wild-type strain. The susceptibilities of these mutants to various in vitro and ex vivo stress conditions were investigated and compared. RESULTS The ΔegtA-mshA mutant was the most susceptible to cellular stress relative to its parent single mutant strains (ΔegtA and ∆mshA) and the other double mutants. In addition, it displayed a growth-defect in vitro, in mouse and human macrophages suggesting; that the complete inhibition of ERG, MSH and GGC biosynthesis is deleterious for the growth of M.tb. CONCLUSIONS This study indicates that ERG, MSH and GGC are able to compensate for each other to maximize the protection and ensure the fitness of M.tb. This study therefore suggests that the most effective strategy to target thiol biosynthesis for anti-tuberculosis drug development would be the simultaneous inhibition of the biosynthesis of ERG, MSH and GGC.
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Affiliation(s)
- C. Sao Emani
- DST-NRF Centre of Excellence for Biomedical Tuberculosis Research; SAMRC Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics; Department of Biomedical Sciences, Faculty of Medicine and Health Sciences; Stellenbosch University, PO Box 241, Francie van Zijl Drive, Tygerberg 8000, Cape Town, South Africa
| | - M. J. Williams
- DST-NRF Centre of Excellence for Biomedical Tuberculosis Research; SAMRC Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics; Department of Biomedical Sciences, Faculty of Medicine and Health Sciences; Stellenbosch University, PO Box 241, Francie van Zijl Drive, Tygerberg 8000, Cape Town, South Africa
| | - I. J. Wiid
- DST-NRF Centre of Excellence for Biomedical Tuberculosis Research; SAMRC Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics; Department of Biomedical Sciences, Faculty of Medicine and Health Sciences; Stellenbosch University, PO Box 241, Francie van Zijl Drive, Tygerberg 8000, Cape Town, South Africa
| | - B. Baker
- DST-NRF Centre of Excellence for Biomedical Tuberculosis Research; SAMRC Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics; Department of Biomedical Sciences, Faculty of Medicine and Health Sciences; Stellenbosch University, PO Box 241, Francie van Zijl Drive, Tygerberg 8000, Cape Town, South Africa
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Sotgia S, Mangoni AA, Forteschi M, Murphy RB, Elliot D, Sotgiu E, Pintus G, Carru C, Zinellu A. Identification of the Main Intermediate Precursor of l-Ergothioneine Biosynthesis in Human Biological Specimens. Molecules 2016; 21:molecules21101298. [PMID: 27689978 PMCID: PMC6272924 DOI: 10.3390/molecules21101298] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 09/10/2016] [Accepted: 09/23/2016] [Indexed: 12/26/2022] Open
Abstract
A capillary electrophoresis coupled to tandem mass spectrometry (CE–MS/MS) has been used to make a qualitative determination of hercynine—the main precursor of l-ergothioneine biosynthesis—in some key human biological specimens, such as urine, whole blood, plasma, and saliva. From semiquantitative analysis results, the highest concentrations of hercynine were detected in saliva and whole blood, whereas much lower concentrations were measured in urine and plasma. Whole blood was the biological matrix with the highest concentration of l-ergothioneine followed by plasma, saliva, and urine. The antioxidant effects attributed to l-ergothioneine, along with its peculiar antioxidant mechanism, offer a possible explanation for the presence of the hercynine, as well as its concentration, in the considered biological matrices.
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Affiliation(s)
- Salvatore Sotgia
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
| | - Arduino A Mangoni
- Department of Clinical Pharmacology, School of Medicine, Flinders University and Flinders Medical Centre, Adelaide SA 5042, Australia.
| | - Mauro Forteschi
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
| | - Rhys B Murphy
- Department of Clinical Pharmacology, School of Medicine, Flinders University and Flinders Medical Centre, Adelaide SA 5042, Australia.
| | - David Elliot
- Department of Clinical Pharmacology, School of Medicine, Flinders University and Flinders Medical Centre, Adelaide SA 5042, Australia.
| | - Elisabetta Sotgiu
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
| | - Gianfranco Pintus
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha 2713, Qatar.
| | - Ciriaco Carru
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
- Quality Control Unit, University Hospital Sassari (AOU), Sassari 07100, Italy.
| | - Angelo Zinellu
- Department of Biomedical Sciences, School of Medicine, University of Sassari, Sassari 07100, Italy.
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Vargas D, Hageman S, Gulati M, Nobile CJ, Rawat M. S-nitrosomycothiol reductase and mycothiol are required for survival under aldehyde stress and biofilm formation in Mycobacterium smegmatis. IUBMB Life 2016; 68:621-8. [PMID: 27321674 DOI: 10.1002/iub.1524] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/11/2016] [Accepted: 05/17/2016] [Indexed: 01/16/2023]
Abstract
We show that Mycobacterium smegmatis mutants disrupted in mscR, coding for a dual function S-nitrosomycothiol reductase and formaldehyde dehydrogenase, and mshC, coding for a mycothiol ligase and lacking mycothiol (MSH), are more susceptible to S-nitrosoglutathione (GSNO) and aldehydes than wild type. MSH is a cofactor for MscR, and both mshC and mscR are induced by GSNO and aldehydes. We also show that a mutant disrupted in egtA, coding for a γ-glutamyl cysteine synthetase and lacking in ergothioneine, is sensitive to nitrosative stress but not to aldehydes. In addition, we find that MSH and S-nitrosomycothiol reductase are required for normal biofilm formation in M. smegmatis, suggesting potential new therapeutic pathways to target to inhibit or disrupt biofilm formation. © 2016 IUBMB Life, 68(8):621-628, 2016.
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Affiliation(s)
- Derek Vargas
- Department of Biology, California State University-Fresno, Fresno, CA, USA
| | - Samantha Hageman
- Department of Biology, California State University-Fresno, Fresno, CA, USA
| | - Megha Gulati
- Department of Molecular and Cell Biology, University of California Merced, Merced, CA, USA
| | - Clarissa J Nobile
- Department of Molecular and Cell Biology, University of California Merced, Merced, CA, USA
| | - Mamta Rawat
- Department of Biology, California State University-Fresno, Fresno, CA, USA
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Liu H, Zhao X, Guo M, Liu H, Zheng Z. Growth and metabolism of Beauveria bassiana spores and mycelia. BMC Microbiol 2015; 15:267. [PMID: 26581712 PMCID: PMC4652391 DOI: 10.1186/s12866-015-0592-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 10/28/2015] [Indexed: 11/19/2022] Open
Abstract
Background Fungi are ubiquitous in nature and have evolved over time to colonize a wide range of ecosystems including pest control. To date, most research has focused on the hypocrealean genera Beauveria bassiana, which is a typical filamentous fungus with a high potential for insect control. The morphology and components of fungi are important during the spores germination and outgrow to mycelia. However, to the best of our knowledge, there is no report on the morphology and components of B. bassiana spores and mycelia. In the work, the growth and metabolism of Beauveria bassiana spores and mycelia were studied. High performance liquid chromatography-mass spectrometry (HPLC-MS) was employed to study the metabolism of B. bassiana spores and mycelia. Principal component analysis (PCA) based on HPLC-MS was conducted to study the different components of the spores and mycelia of the fungus. Metabolic network was established based on HPLC-MS and KEGG database. Results Through Gompertz model based on macroscopic and microscopic techniques, spore elongation length was found to increase exponentially until approximately 23.1 h after cultivation, and then growth became linear. In the metabolic network, the decrease of glyoxylate, pyruvate, fumarate, alanine, succinate, oxaloacetate, dihydrothymine, ribulose, acetylcarnitine, fructose-1, 6-bisphosphate, mycosporin glutamicol, and the increase of betaine, carnitine, ergothioneine, sphingosine, dimethyl guanosine, glycerophospholipids, and in spores indicated that the change of the metabolin can keep spores in inactive conditions, protect spores against harmful effects and survive longer. Conclusions Analysis of the metabolic pathway in which these components participate can reveal the metabolic difference between spores and mycelia, which provide the tools for understand and control the process of of spores germination and outgrow to mycelia.
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Affiliation(s)
- Hongxia Liu
- Jujube Scientific Research and Applied Center, Life Science College, Luoyang Normal University, 471000, Luoyang, P. R. China.
| | - Xusheng Zhao
- Jujube Scientific Research and Applied Center, Life Science College, Luoyang Normal University, 471000, Luoyang, P. R. China.
| | - Mingxin Guo
- Jujube Scientific Research and Applied Center, Life Science College, Luoyang Normal University, 471000, Luoyang, P. R. China.
| | - Hui Liu
- Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui, 230031, P. R. China.
| | - Zhiming Zheng
- Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui, 230031, P. R. China.
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Full Kinetics and a Mechanistic Investigation of the Green Protocol for Synthesis of β-Aminoketone in the Presence of Saccharose as a Catalyst by a One-Pot Three-Component Reaction. ADVANCES IN CHEMICAL PHYSICS 2014. [DOI: 10.1155/2014/426749] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
For the first time, in a green protocol, an investigation of the kinetics and mechanism of the reaction between benzaldehyde 1, 4-chloroanilinne 2, and acetophenone 3 compounds in the presence of saccharose as a catalyst was performed for generating β-aminoketone. For determining the kinetic parameters, the reaction was monitored by using the UV/Vis spectrophotometry technique. The second order rate constant (k1) was automatically calculated by the standard equations contained within the program. In the studied temperature range, the second order rate constant (ln k1, ln k1/T) depended on reciprocal temperature that was in good consistent with Arrhenius and Eyring equations, respectively. These data provided the suitable plots for calculating the activation energy and parameters (Ea, ΔG‡, ΔS‡, and ΔH‡) of the reaction. Furthermore, useful information was obtained from studying the effects of solvent, concentration, and catalyst on the reaction mechanism. The results showed that the first step of the reaction mechanism is a rate determining step (RDS). The obtained experimental data and also the steady state assumption confirmed the proposed mechanism.
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Full kinetics and a mechanistic investigation of three-component reaction catalyzed by sodium acetate leading to 3,4-dihydropyrano[c]chromene. RESEARCH ON CHEMICAL INTERMEDIATES 2014. [DOI: 10.1007/s11164-014-1704-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
SIGNIFICANCE Oxidative stress is widely invoked in inflammation, aging, and complex diseases. To avoid unwanted oxidations, the redox environment of cellular compartments needs to be tightly controlled. The complementary action of oxidoreductases and of high concentrations of low-molecular-weight (LMW) nonprotein thiols plays an essential role in maintaining the redox potential of the cell in balance. RECENT ADVANCES While LMW thiols are central players in an extensive range of redox regulation/metabolism processes, not all organisms use the same thiol cofactors to this effect, as evidenced by the recent discovery of mycothiol (MSH) and bacillithiol (BSH) among different gram-positive bacteria. CRITICAL ISSUES LMW thiol-disulfide exchange processes and their cellular implications are often oversimplified, as only the biology of the free thiols and their symmetrical disulfides is considered. In bacteria under oxidative stress, especially where concentrations of different LMW thiols are comparable [e.g., BSH, coenzyme A (CoA), and cysteine (Cys) in many low-G+C gram-positive bacteria (Firmicutes)], mixed disulfides (e.g., CoASSB and CySSCoA) must surely be major thiol-redox metabolites that need to be taken into consideration. FUTURE DIRECTIONS There are many microorganisms whose LMW thiol-redox buffers have not yet been identified (either bioinformatically or experimentally). Many elements of BSH and MSH redox biochemistry remain to be explored. The fundamental biophysical properties, thiol pK(a) and redox potential, have not yet been determined, and the protein interactome in which the biothiols MSH and BSH are involved needs further exploration.
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Affiliation(s)
- Koen Van Laer
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie (VIB), Brussels, Belgium
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Rahman I. Pharmacological antioxidant strategies as therapeutic interventions for COPD. Biochim Biophys Acta Mol Basis Dis 2011; 1822:714-28. [PMID: 22101076 DOI: 10.1016/j.bbadis.2011.11.004] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 11/01/2011] [Accepted: 11/02/2011] [Indexed: 10/15/2022]
Abstract
Cigarette/tobacco smoke/biomass fuel-induced oxidative and aldehyde/carbonyl stress are intimately associated with the progression and exacerbation of chronic obstructive pulmonary disease (COPD). Therefore, targeting systemic and local oxidative stress with antioxidants/redox modulating agents, or boosting the endogenous levels of antioxidants are likely to have beneficial effects in the treatment/management of COPD. Various antioxidant agents, such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn, erdosteine, fudosteine, ergothioneine, and carbocysteine), have been reported to modulate various cellular and biochemical aspects of COPD. These antioxidants have been found to scavenge and detoxify free radicals and oxidants, regulate of glutathione biosynthesis, control nuclear factor-kappaB (NF-kappaB) activation, and hence inhibiting inflammatory gene expression. Synthetic molecules, such as specific spin traps like α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419, iNOS and myeloperoxidase inhibitors, lipid peroxidation inhibitors/blockers edaravone, and lazaroids/tirilazad have also been shown to have beneficial effects by inhibiting cigarette smoke-induced inflammatory responses and other carbonyl/oxidative stress-induced cellular alterations. A variety of oxidants, free radicals, and carbonyls/aldehydes are implicated in the pathogenesis of COPD, it is therefore, possible that therapeutic administration or supplementation of multiple antioxidants and/or boosting the endogenous levels of antioxidants will be beneficial in the treatment of COPD. This review discusses various novel pharmacological approaches adopted to enhance lung antioxidant levels, and various emerging beneficial and/or prophylactic effects of antioxidant therapeutics in halting or intervening the progression of COPD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.
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Affiliation(s)
- Irfan Rahman
- Department of Environmental Medicine, Lung Biology and Disease Program, University of Rochester Medical Center, NY 14642, USA.
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Hand CE, Taylor NJ, Honek JF. Ab initio studies of the properties of intracellular thiols ergothioneine and ovothiol. Bioorg Med Chem Lett 2005; 15:1357-60. [PMID: 15713386 DOI: 10.1016/j.bmcl.2005.01.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Revised: 01/05/2005] [Accepted: 01/10/2005] [Indexed: 11/30/2022]
Abstract
Intracellular naturally occurring aromatic thiols such as ergothioneine and the ovothiols have been shown to play a variety of roles in cellular function. A detailed ab initio electronic structure analysis of these thiols is reported evaluating the thermodynamics of the reactions of these intracellular thiols with alkyl thiols, HO*, H2O2, ascorbate and their disulfides.
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Affiliation(s)
- Christine E Hand
- Chemistry Department, University of Waterloo, Waterloo, Ontario, Canada
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Bedirli A, Sakrak O, Muhtaroglu S, Soyuer I, Guler I, Riza Erdogan A, Sozuer EM. Ergothioneine pretreatment protects the liver from ischemia-reperfusion injury caused by increasing hepatic heat shock protein 70. J Surg Res 2004; 122:96-102. [PMID: 15522321 DOI: 10.1016/j.jss.2004.06.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Indexed: 12/11/2022]
Abstract
BACKGROUND Reperfusion of the liver after ischemia induces the expression of the heat shock genes and the synthesis of the heat shock proteins (HSP). We studied the effects of the natural antioxidant ergothioneine (EGT) treatment on the expression of HSP70 in ischemic-reperfused (IR) liver. METHODS Adult male Wistar rats were randomly divided into three groups: Sham group given standard laboratory chow and water for 3 weeks followed by sham operation; Control group given standard laboratory chow and water for 3 weeks followed by liver IR injury; EGT group given standard laboratory chow supplementation l-ergothioneine (1.2 mg/kg/d body weight) administered by gavage and water for 3 weeks followed by liver IR injury. Ten rats from each group were killed to determine serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactic dehydrogenase (LDH), tissue malondialdehyde (MDA), HSP70 levels, and histologic changes at 30, 60, and 120 min of reperfusion, respectively. Survival was followed for 1 week. RESULTS IR caused significant increase in serum AST, ALT, LDH, and tissue MDA levels. As compared with the control group, animals treated with EGT experienced a significant decrease in serum AST, ALT, and LDH levels in all reperfusion periods. Tissue MDA levels in animals receiving EGT were significantly reduced as compared with control group at 30 min and 60 min after reperfusion. After ischemia, reperfusion caused a remarkable production of HSP70 in the control group. When the rats were pretreated with EGT, the levels of HSP70 increased significantly in their livers after reperfusion compared with the control group. Liver injury in the EGT-treated animals was lower to that in the control group. The 7-day survival rate was significantly improved (from 50% to 80%) by EGT pretreatment. CONCLUSION HSP70 has been shown to induce tolerance against warm IR injury in rat livers. EGT pretreatment protects the liver from IR injury by over-expression of HSP and the subsequent suppression of lipid peroxidation.
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Affiliation(s)
- Abdulkadir Bedirli
- Department of General Surgery, University of Gazi, School of Medicine, Ankara, Turkey.
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Abu-Shakra A. The mutagenic activity of the S-nitrosoglutathione/glutathione system in Salmonella typhimurium TA1535. Mutat Res 2003; 539:203-6. [PMID: 12948829 DOI: 10.1016/s1383-5718(03)00131-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
S-nitrosoglutathine (GSNO) and reduced glutathione (GSH) were tested for mutagenicity against strain Salmonella typhimurium TA1535 in the Ames Standard plate incorporation assay. Neither GSNO not GSH were mutagenic when tested alone. In combination, the GSNO/GSH system induced a positive mutagenic response that ranged from 3 to 20 x over background at concentrations of 10 to 50 micromol (micromol)per plate, respectively. This mutagenic response can be attributable to the generation nitric oxide, among the many other reactive products generated by the reaction of GSNO with GSH.
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Affiliation(s)
- Amal Abu-Shakra
- Department of Biology, North Carolina Central University, 1801 Fayetteville Street, Durham, NC 27707, USA.
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Vogt RN, Steenkamp DJ. The metabolism of S-nitrosothiols in the trypanosomatids: the role of ovothiol A and trypanothione. Biochem J 2003; 371:49-59. [PMID: 12487629 PMCID: PMC1223258 DOI: 10.1042/bj20021649] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2002] [Revised: 12/10/2002] [Accepted: 12/17/2002] [Indexed: 11/17/2022]
Abstract
It has recently been established that nitrosoglutathione is the preferred substrate of the glutathione-dependent formaldehyde dehydrogenase from divergent organisms. Trypanosomatids produce not only glutathione, but also glutathionylspermidine, trypanothione and ovothiol A. The formaldehyde dehydrogenase activity of Crithidia fasciculata was independent of these thiols and extracts possessed very low levels of nitrosothiol reductase activity with glutathione or its spermidine conjugates as the thiol component. Although ovothiol A did not form a stable nitrosothiol, it decomposed the S -nitroso groups of nitrosoglutathione (GSNO) and dinitrotrypanothione [T(SNO)(2)] with second-order rate constants of 19.12 M(-1) x s(-1) and 8.67 M(-1) x s(-1) respectively. The reaction of T(SNO)(2) with ovothiol A, however, accelerated to a rate similar to that seen with GSNO. Ovothiol A can act catalytically to decompose these nitrosothiols, although non-productive mechanisms exist. The catalytic phase of the reaction was dependent on the production of thiyl radicals, since it was abolished in the presence of 5,5-dimethyl-1-pyrroline- N -oxide and the formation of nitric oxide could be detected by means of the conversion of oxyhaemoglobin into methaemoglobin. The rate-limiting step in the catalytic process was the reduction of oxidized ovothiol species and, in this respect, T(SNO)(2) is a more efficient substrate than GSNO. Trypanothione decomposed GSNO with a second-order rate constant of 0.786 M(-1) x s(-1) and the major nitrogenous end product changed from nitrite to ammonia as the ratio of thiol to nitrosothiol increased. The results indicate that ovothiol A acts in synergy with trypanothione in the decomposition of T(SNO)(2).
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Affiliation(s)
- Ryan N Vogt
- Division of Chemical Pathology, Department of Laboratory Medicine, University of Cape Town Medical School, Observatory, 7925, South Africa
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