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Maria Wrobel - One of the best experts on this subject based on the ideXlab platform.
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H2S, Polysulfides, and Enzymes: Physiological and Pathological Aspects
Biomolecules, 2020Co-Authors: Noriyuki Nagahara, Maria WrobelAbstract:We have been studying the general aspects of the functions of H2S and polysulfides, and the enzymes involved in their biosynthesis, for more than 20 years. Our aim has been to elucidate novel physiological and pathological functions of H2S and polysulfides, and unravel the regulation of the enzymes involved in their biosynthesis, including cystathionine β-synthase (EC 4.2.1.22), cystathionine γ-lyase (EC 4.4.1.1), thiosulfate Sulfurtransferase (rhodanese, EC 2.8.1.1), and 3-mercaptopyruvate Sulfurtransferase (EC 2.8.1.2). Physiological and pathological functions, alternative biosynthetic processes, and additional functions of H2S and polysulfides have been reported. Further, the structure and reaction mechanisms of related enzymes have also been reported. We expect this issue to advance scientific knowledge regarding the detailed functions of H2S and polysulfides as well as the general properties and regulation of the enzymes involved in their metabolism. We would like to cover four topics: the physiological and pathological functions of H2S and polysulfides, the mechanisms of the biosynthesis of H2S and polysulfides, the properties of the biosynthetic enzymes, and the regulation of enzymatic activity. The knockout mouse technique is a useful tool to determine new physiological functions, especially those of H2S and polysulfides. In the future, we shall take a closer look at symptoms in the human congenital deficiency of each enzyme. Further studies on the regulation of enzymatic activity by in vivo substances may be the key to finding new functions of H2S and polysulfides.
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A possible mechanism of inhibition of U87MG and SH-SY5Y cancer cell proliferation by diallyl trisulfide and other aspects of its activity
Amino Acids, 2017Co-Authors: Halina Jurkowska, Maria Wrobel, Marta Kaczor-kamińska, Ewa Jasek-gajdaAbstract:The study was conducted to elucidate the mechanism of antiproliferative and antioxidative action of diallyl trisulfide (DATS), a garlic-derived organosulfur compound. Changes in the l -cysteine desulfuration, and the levels of cystathionine and non-protein thiols in DATS-treated human glioblastoma (U87MG) and neuroblastoma (SH-SY5Y) cells were investigated. The inhibition of proliferation of the investigated cells by DATS was correlated with an increase in the inactivated form of Bcl-2. In U87MG cells, an increased level of sulfane sulfur and an increased activity of 3-mercaptopyruvate Sulfurtransferase (MPST) and rhodanese, the enzymes involved in sulfane sulfur generation and transfer, suggest that DATS can function as a donor of sulfane sulfur atom, transferred by Sulfurtransferases, to sulfhydryl groups of cysteine residues of Bcl-2 and in this way lower the level of active form of Bcl-2 by S -sulfuration. Diallyl trisulfide antioxidative effects result from an increased level of cystathionine, a precursor of cysteine, and an increased glutathione level. MPST and rhodanese, the level of which is increased in the presence of DATS, can serve as antioxidant proteins.
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exposure to lead in water and cysteine non oxidative metabolism in pelophylax ridibundus tissues
Aquatic Toxicology, 2013Co-Authors: Marta Kaczor, Patrycja Bronowickaadamska, Piotr Sura, Maria WrobelAbstract:Abstract Chronic, low-level exposure to metals is an increasing global problem. Lead is an environmentally persistent toxin that causes many lead-related pathologies, directly affects tissues and cellular components or exerts an effect of the generation of reactive oxygen species causing a diminished level of available sulfhydryl antioxidant reserves. Cysteine is one of substrates in the synthesis of glutathione – the most important cellular antioxidant, and it may also undergo non-oxidative desulfuration that produces compounds containing sulfane sulfur atoms. The aim of the experiment was to examine changes of the non-oxidative metabolism of cysteine and the levels of cysteine and glutathione in the kidneys, heart, brain, liver and muscle of Marsh frogs (Pelophylax ridibundus) exposed to 28 mg/L Pb(NO3)2 for 10 days. The activities of Sulfurtransferases, enzymes related to the sulfane sulfur metabolism – 3-mercaptopyruvate sulfurtransfearse, γ-cystathionase and rhodanese – were detected in tissue homogenates. The activity of Sulfurtransferases was much higher in the kidneys of frogs exposed to lead in comparison to control frogs, not exposed to lead. The level of sulfane sulfur remained unchanged. Similarly, the total level of cysteine did not change significantly. The total levels of glutathione and the cysteine/cystine and GSH/GSSG ratios were elevated. Thus, it seems that the exposure to lead intensified the metabolism of sulfane sulfur and glutathione synthesis in the kidneys. The results presented in this work not only confirm the participation of GSH in the detoxification of lead ions and/or products appearing in response to their presence, such as reactive oxygen species, but also indicate the involvement of sulfane sulfur and rhodanese in this process (e.g. brain). As long as the expression of enzymatic proteins (rhodanese, MPST and CST) is not examined, no answer will be provided to the question whether changes in their activity are due to differences in the concentrations of substrates and/or compounds affecting their activity or to changes in their level in response to some parameters, e.g. associated with oxidative stress.
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Changes in Activity of Three Sulfurtransferases in Response to Exposure to Cadmium, Lead and Mercury Ions
Journal of Environmental Protection, 2013Co-Authors: Marta Kaczor-kamińska, Piotr Sura, Maria WrobelAbstract:Cadmium, lead and mercury are environmentally persistent toxicants that affect tissues and cellular components or exert an effect on generation of reactive oxygen species causing a decreased level of available antioxidant reserves. Sulfurtransferases are enzymes that are widespread in nature. Rhodanese, 3-mercaptopyruvate Sulfurtransferase and γ-cystathionase play an important role in the metabolism of L-cysteine. Heavy metal ions can bind to -SH groups of cysteine residues in their active sites and, therefore, decrease the activity of these enzymes and result in changes in the level of sulfane sulfur-containing compounds, products of L-cysteine desulfuration. Changes in the activity of Sulfurtransferases were investigated in the kidneys, heart, brain, liver and skeletal muscle of Marsh frogs (Pelophylax ridibundus) after 10 days of exposure to Pb(NO3)2 at the concentration of 28 mg/L and CdCl2 at the concentration of 40 mg or 80 mg/L, and in Xenopus laevies tissues after 7 and 14 days of exposure to HgCl2 at the concentration of 1.353 mg/L. The investigated heavy metal ions have a tendency to inhibit the activity of Sulfurtransferases and decrease the level of glutathione, what can result in oxidative stress and oxidation of cysteine -SH groups to -SOH. This reversible oxidation and reduction of these redox sensitive groups can play a role in defenses against oxidative stress. Based on the presented results, one can surmise that also the expression of the three Sulfurtransferases depends on heavy metal ions and/or some parameters of oxidative stress, what can explain the increase of the activity of MPST and CST in the kidney.
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effect of mercury ions on cysteine metabolism in xenopus laevis tissues
Comparative Biochemistry and Physiology, 2011Co-Authors: Piotr Sura, Patrycja Bronowickaadamska, Elzbieta Furtak, Maria WrobelAbstract:The effect of mercury ions on the level of cysteine, glutathione, sulfane sulfur, and on the activity of rhodanese, 3-mercaptopyruvate Sulfurtransferase (MPST) and γ-cystathionase in brain, heart muscle, liver, kidneys, testes and skeletal muscle of adult Xenopus laevis was investigated. Frogs of both sexes were exposed for 7 or 14days to 1.353mgL⁻¹ (ppm) of mercury chloride (HgCl₂) dissolved in water. The activity of the investigated enzymes participating in cysteine metabolism depends on cysteine in their active sites. Mercury ions can bind to –SH groups and, therefore, lower the activity of enzymes and change the level of sulfane sulfur, a product of l-cysteine desulfuration. The effect of mercury was found to depend on the time of exposure and the kind of tissue. In the liver, the main site of glutathione biosynthesis, the ratio of GSH to GSSG was essentially unchanged. The total glutathione level was decreased after 7days of exposure to mercury, similarly as the activity of rhodanese. Sulfane sulfur levels were significantly increased after a shorter duration, while they decreased after a longer time of exposure. The kidney, brain and testes were able to enhance the level of GSH, probably thanks to high γ-glutamyltranspeptidase activity. These tissues showed an increased value of GSH/GSSG ratio during the shorter exposure to mercury. The activity of Sulfurtransferases was decreased, especially after the longer exposure to mercury. In the heart and skeletal muscle, the level of GSH, sulfane sulfur, and the activity of the investigated Sulfurtransferases was diminished after 14days of exposure to Hg. It can be concluded that the main mechanism of toxic Hg activity is generation of reactive oxygen species in cells due to depleted GSH level, and a decreased Sulfurtransferases activity either by blocking or oxidation of their –SH groups, what in consequence results in a diminished sulfane sulfur levels in tissues, especially the heart and testes.
Rahul Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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Dose and Time‐Dependent Effects of Cyanide on Thiosulfate Sulfurtransferase, 3‐Mercaptopyruvate Sulfurtransferase, and Cystathionine λ‐Lyase Activities
Journal of Biochemical and Molecular Toxicology, 2013Co-Authors: Poonam Singh, Pooja Rao, Rahul BhattacharyaAbstract:We assessed the dose-dependent effect of potassium cyanide (KCN) on thiosulfate Sulfurtransferase (TST), 3-mercaptopyruvate Sulfurtransferase (3-MPST), and cystathionine λ-lyase (CST) activities in mice. The time-dependent effect of 0.5 LD50 KCN on cyanide level and cytochrome c oxidase (CCO), TST, 3-MPST, and CST activities was also examined. Furthermore, TST, 3-MPST, and CST activities were measured in stored mice cadavers. Hepatic and renal TST activity increased by 0.5 LD50 KCN but diminished by ≥2.0 LD50. After 0.5 LD50 KCN, the elevated hepatic cyanide level was accompanied by increased TST, 3-MPST, and CST activities, and CCO inhibition. Elevated renal cyanide level was only accompanied by increased 3-MPST activity. No appreciable change in enzyme activities was observed in mice cadavers. The study concludes that high doses of cyanide exert saturating effects on its detoxification enzymes, indicating their exogenous use during cyanide poisoning. Also, these enzymes are not reliable markers of cyanide poisoning in autopsied samples.
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dose and time dependent effects of cyanide on thiosulfate Sulfurtransferase 3 mercaptopyruvate Sulfurtransferase and cystathionine λ lyase activities
Journal of Biochemical and Molecular Toxicology, 2013Co-Authors: Poonam Singh, Pooja Rao, Rahul BhattacharyaAbstract:We assessed the dose-dependent effect of potassium cyanide (KCN) on thiosulfate Sulfurtransferase (TST), 3-mercaptopyruvate Sulfurtransferase (3-MPST), and cystathionine λ-lyase (CST) activities in mice. The time-dependent effect of 0.5 LD50 KCN on cyanide level and cytochrome c oxidase (CCO), TST, 3-MPST, and CST activities was also examined. Furthermore, TST, 3-MPST, and CST activities were measured in stored mice cadavers. Hepatic and renal TST activity increased by 0.5 LD50 KCN but diminished by ≥2.0 LD50. After 0.5 LD50 KCN, the elevated hepatic cyanide level was accompanied by increased TST, 3-MPST, and CST activities, and CCO inhibition. Elevated renal cyanide level was only accompanied by increased 3-MPST activity. No appreciable change in enzyme activities was observed in mice cadavers. The study concludes that high doses of cyanide exert saturating effects on its detoxification enzymes, indicating their exogenous use during cyanide poisoning. Also, these enzymes are not reliable markers of cyanide poisoning in autopsied samples.
Silvia Pagani - One of the best experts on this subject based on the ideXlab platform.
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Enzymatic and genetic profiles in environmental strains grown on polycyclic aromatic hydrocarbons
Antonie van Leeuwenhoek, 2007Co-Authors: Lucia Cavalca, Silvia Pagani, Nicoletta Guerrieri, Milena Colombo, Vincenza AndreoniAbstract:The possible generation of oxidative stress induced by aromatic hydrocarbon degradation suggests that ancillary enzyme activities could facilitate the utilization of polycyclic aromatic hydrocarbons as sole carbon source. To investigate the metabolic profiles of low molecular weight polycyclic aromatic hydrocarbon-degrading strains of Sphingobium chlorophenolicum , Rhodococcus aetherovorans , Rhodococcus opacus and Mycobacterium smegmatis , the determination of the activity of putative detoxifying enzymes (rhodanese-like and glutathione S -transferase proteins) was combined with genetic analyses. All the studied strains were able to utilize phenanthrene or naphthalene. Glutathione S -transferase activity was found in S. chlorophenolicum strains grown on phenanthrene and it was related to the presence of the bphK gene, since modulation of glutathione S -transferase activity by phenanthrene paralleled the induction of glutathione S -transferase transcript in the S. chlorophenolicum strains. No glutathione S -transferase activity was detectable in R. aetherovorans, R. opacus and in M. smegmatis strains. All strains showed 3-mercaptopyruvate:cyanide Sulfurtransferase activity. A rhodanese-like SseA protein was immunodetected in R. aetherovorans , R. opacus and in M. smegmatis strains, where increase of 3-mercaptopyruvate:cyanide Sulfurtransferase activity was significantly induced by growth on phenanthrene.
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The "Rhodanese" Fold and Catalytic Mechanism of 3-Mercaptopyruvate Sulfurtransferases: Crystal Structure of SseA from Escherichia coli
Journal of Molecular Biology, 2004Co-Authors: Andrea Spallarossa, Aristodemo Carpen, Fabio Forlani, Silvia Pagani, Martino Bolognesi, Andrea Armirotti, Domenico BordoAbstract:3-Mercaptopyruvate Sulfurtransferases (MSTs) catalyze, in vitro, the transfer of a sulfur atom from substrate to cyanide, yielding pyruvate and thiocyanate as products. They display clear structural homology with the protein fold observed in the rhodanese Sulfurtransferase family, composed of two structurally related domains. The role of MSTs in vivo, as well as their detailed molecular mechanisms of action have been little investigated. Here, we report the crystal structure of SseA, a MST from Escherichia coli, which is the first MST three-dimensional structure disclosed to date. SseA displays specific structural differences relative to eukaryotic and prokaryotic rhodaneses. In particular, conformational variation of the rhodanese active site loop, hosting the family invariant catalytic Cys residue, may support a new sulfur transfer mechanism involving Cys237 as the nucleophilic species and His66, Arg102 and Asp262 as residues assisting catalysis.
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SseA, a 3-mercaptopyruvate Sulfurtransferase from Escherichia coli: crystallization and preliminary crystallographic data.
Acta Crystallographica Section D Biological Crystallography, 2002Co-Authors: Andrea Spallarossa, Aristodemo Carpen, Fabio Forlani, Silvia Pagani, Martino Bolognesi, Domenico BordoAbstract:SseA, the translation product of the Escherichia coli sseA gene, is a 31 kDa protein endowed with 3-mercaptopyruvate:cyanide Sulfurtransferase activity in vitro. As such, SseA is the prototype of a Sulfurtransferase subfamily distinguished from the better known rhodanese Sulfurtransferases, which display thiosulfate:cyanide Sulfurtransferase activity. The physiological role of the two homologous enzyme families, whose catalytic activity is centred on a reactive invariant cysteine, is a matter of debate. In this framework, the forthcoming crystal structure analysis of SseA will be based on the tetragonal crystal form (space group P4(1) or P4(3)) reported here, with unit-cell parameters a = b = 150.2, c = 37.9 A.
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Mutagenic analysis of Thr‐232 in rhodanese from Azotobacter vinelandii highlighted the differences of this prokaryotic enzyme from the known Sulfurtransferases
FEBS Letters, 2000Co-Authors: Silvia Pagani, Aristodemo Carpen, Fabio Forlani, Domenico Bordo, Rita ColnaghiAbstract:Azotobacter vinelandii RhdA uses thiosulfate as the only sulfur donor in vitro, and this apparent selectivity seems to be a unique property among the characterized Sulfurtransferases. To investigate the basis of substrate recognition in RhdA, we replaced Thr-232 with either Ala or Lys. Thr-232 was the target of this study since the corresponding Lys-249 in bovine rhodanese has been identified as necessary for catalytic sulfur transfer, and replacement of Lys-249 with Ala fully inactivates bovine rhodanese. Both T232K and T232A mutants of RhdA showed significant increase in thiosulfate-cyanide Sulfurtransferase activity, and no detectable activity in the presence of 3-mercaptopyruvate as the sulfur donor substrate. Fluorescence measurements showed that wild-type and mutant RhdAs were overexpressed in the persulfurated form, thus conferring to this enzyme the potential of a persulfide sulfur donor compound. RhdA contains a unique sequence stretch around the catalytic cysteine, and the data here presented suggest a possible divergent physiological function of A. vinelandii Sulfurtransferase.
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identification of Sulfurtransferase enzymes in azotobacter vinelandii
FEBS Letters, 1991Co-Authors: Silvia Pagani, Rita Colnaghi, E Franchi, C KennedyAbstract:Abstract Rhodanese and 3-mercaptopyruvate sulphurtransferase have been identified in A. vinelandii . Two distinct active fractions of the two sulphurtransferases were obtained after FPLC ion-exchange chromatography of material partially purified from crude extracts. Rhodanese has been purified to homogeneity, and it consists of one polypeptide chain of M r ca 25 000. A partial purification of 3-mercaptopyruvate sulphurtransferase was obtained.
Zhi-wu Chen - One of the best experts on this subject based on the ideXlab platform.
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3-Mercaptopyruvate Sulfurtransferase/hydrogen sulfide protects cerebral endothelial cells against oxygen-glucose deprivation/reoxygenation-induced injury via mitoprotection and inhibition of the RhoA/ROCK pathway.
American Journal of Physiology-Cell Physiology, 2020Co-Authors: Fang Zhang, Shuo Chen, Ji-yue Wen, Zhi-wu ChenAbstract:3-mercaptopyruvate Sulfurtransferase (3-MST) is the major source of hydrogen sulfide (H2S) production in the brain and participates in many physiological and pathological processes. The present stu...
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3 mercaptopyruvate Sulfurtransferase hydrogen sulfide protects cerebral endothelial cells against oxygen glucose deprivation reoxygenation induced injury via mitoprotection and inhibition of the rhoa rock pathway
American Journal of Physiology-cell Physiology, 2020Co-Authors: Fang Zhang, Shuo Chen, Ji-yue Wen, Zhi-wu ChenAbstract:3-mercaptopyruvate Sulfurtransferase (3-MST) is the major source of hydrogen sulfide (H2S) production in the brain and participates in many physiological and pathological processes. The present stu...
Steven I. Baskin - One of the best experts on this subject based on the ideXlab platform.
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the effect of three α keto acids on 3 mercaptopyruvate Sulfurtransferase activity
Journal of Biochemical Toxicology, 1996Co-Authors: Dale W. Porter, Steven I. BaskinAbstract:3-Mercaptopyruvate Sulfurtransferase catalyzes the transfer of sulfur from 3-mercaptopyruvate to several possible acceptor molecules, one of which is cyanide. Because the transsulfuration of cyanide is the primary in vivo mechanism of detoxification, 3-mercaptopyruvate Sulfurtransferase may function in the enzymatic detoxification of cyanide in vivo. Three alpha-keto acids (alpha-ketobutyrate, alpha-ketoglutarate, and pyruvate) have previously been demonstrated to be cyanide antidotes in vivo, and it has been suggested that this is due to the nonenzymatic binding of cyanide by the alpha-keto acid. However, it has also been proposed that alpha-keto acids may increase the activity of enzymes involved in the transsulfuration of cyanide. Thus, the effect of these three alpha-keto acids on the enzyme 3-mercaptopyruvate Sulfurtransferase was examined. All three alpha-keto acids inhibited 3-mercaptopyruvate Sulfurtransferase in a concentration-dependent manner and were determined to be uncompetitive inhibitors of MST with respect to 3-mercaptopyruvate. The inhibitor constant Ki was estimated by two methods for each inhibitor and ranged from 4.3 to 6.3 mM. The I50, which is the inhibitor concentration that produces 50% inhibition, was calculated for all three alpha-keto acids and ranged between 9.5 and 13.7 mM. These observations add further support to the hypothesis that the mechanism of the alpha-keto acid antidotes is the nonenzymatic binding of cyanide, not stimulation of enzymes involved in the transsulfuration of cyanide to thiocyanate.
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The effect of three α‐keto acids on 3‐mercaptopyruvate Sulfurtransferase activity
Journal of Biochemical Toxicology, 1996Co-Authors: Dale W. Porter, Steven I. BaskinAbstract:3-Mercaptopyruvate Sulfurtransferase catalyzes the transfer of sulfur from 3-mercaptopyruvate to several possible acceptor molecules, one of which is cyanide. Because the transsulfuration of cyanide is the primary in vivo mechanism of detoxification, 3-mercaptopyruvate Sulfurtransferase may function in the enzymatic detoxification of cyanide in vivo. Three alpha-keto acids (alpha-ketobutyrate, alpha-ketoglutarate, and pyruvate) have previously been demonstrated to be cyanide antidotes in vivo, and it has been suggested that this is due to the nonenzymatic binding of cyanide by the alpha-keto acid. However, it has also been proposed that alpha-keto acids may increase the activity of enzymes involved in the transsulfuration of cyanide. Thus, the effect of these three alpha-keto acids on the enzyme 3-mercaptopyruvate Sulfurtransferase was examined. All three alpha-keto acids inhibited 3-mercaptopyruvate Sulfurtransferase in a concentration-dependent manner and were determined to be uncompetitive inhibitors of MST with respect to 3-mercaptopyruvate. The inhibitor constant Ki was estimated by two methods for each inhibitor and ranged from 4.3 to 6.3 mM. The I50, which is the inhibitor concentration that produces 50% inhibition, was calculated for all three alpha-keto acids and ranged between 9.5 and 13.7 mM. These observations add further support to the hypothesis that the mechanism of the alpha-keto acid antidotes is the nonenzymatic binding of cyanide, not stimulation of enzymes involved in the transsulfuration of cyanide to thiocyanate.
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Specificity studies of 3-mercaptopyruvate Sulfurtransferase†
Journal of Biochemical Toxicology, 1995Co-Authors: Dale W. Porter, Steven I. BaskinAbstract:3-Mercaptopyruvate Sulfurtransferase (E.C. 2.8.1.2; MST) is an enzyme believed to function in the endogenous cyanide (CN) detoxification system because it is capable of transferring sulfur from 3-mercaptopyruvate (3-MP) to CN, forming the less toxic thiocyanate (SCN). To date, 3-MP is the only known sulfur-donor substrate for MST. In an effort to increase the understanding of what chemical properties of 3-MP affect its utilization as a substrate, in vitro enzyme kinetic studies of MST were conducted using two mercaptic acids that are structurally related to 3-MP. Neither of these compounds was able to serve as a sulfur-donor substrate for MST. Inhibitor studies determined that 3-mercaptopropionic acid did not affect the Km of MST for 3-MP but did decrease Vmax and, thus, was determined to be a noncompetitive inhibitor. Alternatively, 2-mercaptopropionic acid 2-MPA decreased Km and Vmax and was determined to be an uncompetitive inhibitor of MST with respect to 3-MP. These data indicate that the α-keto group of 3-MP is necessary for its utilization as a substrate, and the inhibitor studies suggest that the position of the sulfur may also affect the binding of these compounds to the enzyme. These observations increase the understanding of what factors can affect the utilization of a compound as a sulfur-donor substrate for MST and may aid in the development of alternative sulfur-donor substrates for MST. © 1996 John Wiley & Sons, Inc.
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Modifiers of mercaptopyruvate Sulfurtransferase catalyzed conversion of cyanide to thiocyanate in vitro.
Journal of Biochemical Toxicology, 1992Co-Authors: David A. Wing, Steven I. BaskinAbstract:The enzyme mercaptopyruvate Sulfurtransferase appears to play an important role in the in vivo detoxification of cyanide. It does so by transferring sulfur to cyanide to produce thiocyanate, which is less toxic and may be excreted through the kidney. Several compounds were tested for their ability to affect the rate of enzyme catalyzed thiocyanate formation in vitro. The studies were carried out using both a partially purified bovine kidney extract and a highly purified enzyme preparation. Hypotaurine and methanesulfinic acid doubled Sulfurtransferase activity in the partially purified extract at 30 mM, but inhibited the purified enzyme to 57% (hypotaurine) and 27% (methanesulfinic acid) of control activity at the same concentration. Pyruvate, phenylpyruvate, oxobutyrate, and oxoglutarate each inhibited the extract and purified forms of mercaptopyruvate Sulfurtransferase. Phenylpyruvate was the most effective inhibitor, reducing activity to 0.2% of control values in the extract, and 11% of control values for purified MPST when added to the reaction at 30 mM. Other compounds tested (see Table 1) had a negligible effect on Sulfurtransferase activity. A heat stable cofactor was found in boiled kidney extract which stimulated Sulfurtransferase activity in the extract but inhibited Sulfurtransferase activity in the purified enzyme, as was observed for hypotaurine and methanesulfinate. The boiled extract had no thiocyanate forming activity of its own. The cofactor operated in synergy with methanesulfinate, but independently of hypotaurine.
