Thiosulfate Reductase Research Articles

Subcellular distribution and intramitochondrial localization of three sulfurtransferases in rat liver

Mammalian tissues contain three enzymes involved in the transfer of bivalent sulphur to a variety .of nucleophilic acceptors: rhodanese (thiosulfate sulfurtransferase, EC 2.8.1. l), 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2) and thiosulfate reductase (no EC number, for definition see [l-4] ). These enzymes participate in the metabolism of some amino acids and low molecular weight sulphur compounds [5-71, show detoxifying activity against sulphide [8] and cyanide [9, IO], are probably involved in the formation of iron-sulfur chromophore of ferredoxin [ 11,121 and restoration of labile sulfur in succinate dehydrogenase (EC 1.3.99. I [ 131). Rhodanese is present solely in the mitochondria [ 14,151 and shows a characteristic latency [ 161, but the subcellular distribution of the two other sulfurtransferases is still disputed. Kun and Fanshier [ 171 and Van der Hamer et al. [ 181 observed that most of the mercaptopyruvate sulfurtransferase activity was in the soluble fraction of rat liver, while recently Taniguchi and Kimura [ 121 found the enzyme in both mitochondria and the cytosol of bovine adrenal cortex. Preliminary observations indicate that also thiosulfate reductase occurs in these two subcellular compartments [ 191. The experiments described here confirm the bimodal intracellular localization of mercaptopyruvate sulfurtransferase and thiosulfate reductase. They also indicate that, within the

The enzymology of sulfur metabolism in phototrophic bacteria — A review

The two functions of sulfur metabolism in phototrophic bacteria are to supply electrons for photosynthesis and to supply sulfur for biosynthetic purposes. The pathways for both functions may be partly identical. For the electron-supplying pathway the following enzymes are needed: a sulfide-oxidizing enzyme, a sulfur-oxidizing enzyme system, APS reductase, ADP sulfurylase and — in the case of thiosulfate utilization — thiosulfate reductase. Assimilatory reactions are catalyzed by ATP sulfurylase, APS kinase, sulfotransferases, PAPS reductase, sulfite reductase and o-acetylserine sulfhydrylase.

Thiosulfate metabolism in some red phototrophic bacteria

The ability to grow phototrophically with thiosulfate as the sole electron donor is widespread among phototrophic bacteria.Chromatium vinosum, C. minus andRhodopseudomonas palustris metabolize thiosulfate constitutively independent of pre-culture conditions. Cell-free extracts of these organisms contain the thiosulfate cleaving enzymes rhodanese and thiosulfate reductase. These enzymes were enriched and partially purified. The present detailed study of their enzymatic properties lead to the assumption that the two enzymes are non-identical.

Purification and properties of thiosulfate reductase from Desulfovibrio gigas

Thiosulfate reductase of the dissimilatory sulfate-reducing bacterium Desulfovibrio gigas has been purified 415-fold and its properties investigated. The enzyme was unstable during the different steps of purification as well as during storage at - 15 degrees C. The molecular weight of thiosulfate reductase estimated from the chromatographic behaviour of the enzyme on Sephadex G-200 was close to 220000. The absorption spectrum of the purified enzyme exhibited a protein peak at 278 nm without characteristic features in the visible region. Thiosulfate reductase catalyzed the stoichiometric production of hydrogen sulfide and sulfite from thiosulfate, and exhibited tetrathionate reductase activity. It did not show sulfite reductase activity. The optimum pH of thiosulfate reduction occurred between pH 7.4 and 8.0 and its Km value for thiosulfate was calculated to be 5 - 10(-4)M. The sensitivity of thiosulfate reductase to sulfhydryl reagent and the reversal of the inhibition by cysteine indicated that one or more sulfhydryl groups were involved in the catalytic activity. The study of electron transport between hydrogenase and thiosulfate reductase showed that the most efficient coupling was obtained with a system containing cytochromes c3 (Mr = 13000) and c3 (Mr = 26000).

Mapping of chlorate-resistant mutants of Citrobacter freundii by deletion and complementation analysis

From Citrobacter freundii mutants have been isolated, with deletions extending chl genes. 53% of these mutants mapped in the gal-bio region of the chromosome. Genetic mapping by three methods—deletion analysis, linkage analysis in crosses with C. freundii Hfr donors and complementation with Escherichia coli F′ factors—establishes the gene order: chl H-gal-chl D-hut-bio-uvr B-chl A-chl I-chl E In an other segment a gene order ilv-chl-pdx was found. Furthermore chl loci were found adjacent to 7 different chromosomal markers. C. freundii can form nitrate reductase A, thiosulfate reductase, tetrathionate reductase and formic dehydrogenase. These enzymes are not formed in most of the chlorate-resistant mutants. In some of these mutants the enzyme activities can be restored by complementation with F′ factors of E. coli.

Observations on the rhodanese activity of Desulfotomaculum nigrificans.

Rhodanese activity, partially purified from Desulfotomaculum nigrificans, was shown to reside in a protein fraction separate from thiosulfate reductase.

Thiosulfate reductase of Desulfovibrio vulgaris.

The thiosulfate reductase of Desulfovibrio vulgaris has been purified and some of its properties have been determined. Only one protein component was detected when the purified enzyme was subjected to polyacrylamide gel electrophoresis at pH values of 8.9, 8.0, and 7.6. In the presence of H(2), the enzyme, when coupled to hydrogenase and with methyl viologen as an electron carrier, catalyzed the reduction of thiosulfate to hydogen sulfide. The use of specifically labeled (35)S-thiosulfate revealed that the outer sulfur atom was reduced to sulfide and the inner sulfur atom was released as sulfite. Thus, the enzyme catalyzes the reductive dismutation of thiosulfate to sulfide and sulfite. The molecular weight of the enzyme was determined by sedimentation equilibrium (16,300) and amino acid analysis (15,500). The enzyme sedimented as a single, symmetrical component with a calculated sedimentation coefficient of 2.21S. Amino acid analysis revealed the presence of two half-cystine residues per mole of enzyme and a total of 128 amino acid residues. Carbohydrate and organic phosphorus analyses revealed the presence of 9.2 moles of carbohydrate and 4.8 moles of phosphate per mole of enzyme. The substrate specificity of the enzyme was studied.

Regulation of reductase formation in Proteus mirabilis

Summary. The levels of several redox enzymes in a chlorate-resistant mutant of Proteus mirabilis, which is partially affected in the formation of formate hydrogenlyase, thiosulfate reductase and tetrathionate reductase, were compared with those of the wild type. The composition of the electron transport system of both strains was almost the same in cells grown aerobically, but very different in cells grown anaerobically. In the mutant, the cytochrome content increased twofold, whereas the level of the anaerobic enzymes is strongly diminished. The anaerobic formation of electron transport components in the mutant was, in contrast to that of the wild type, not influenced significantly by azide. During anaerobic growth with nitrate low levels of a functional nitrate reductase system were formed in the mutant. Under these conditions the formation of formate dehydrogenase, formate hydrogenlyase, formate oxidase, thiosulfate reductase, tetrathionate reductase, cytochromc ha83, 5 and partly that of cytochrome a 2, was repressed. The repressive effect of nitrate, however, was completely abolished by azide. Therefore, it seems likely that a functional nitrate reductase system, rather than nitrate, controls the formation of the enzymes repressible by nitrate.

A genetical and biochemical study of chlorate-resistant mutants of Salmonella typhimurium.

S.typhimurium can form nitrate reductase A, chlorate reductase C, thiosulfate reductase, tetrathionate reductase and formic dehydrogenase. None of these enzymes are formed in chlorate-resistant mutants. Conjugation experiments showed the presence of a strong linkage between thechl andgal markers of the bacterial chromosome. By deletion mapping the gene ordernic A aro G gal bio chl D uvr B chl A was found. Strains with deletions terminating betweenbio anduvr B or betweenuvr B andchl A have a number of aberrant properties. Though resistant against chlorate they reduce nitrate and form gas. After growth with nitrate they form less nitrate reductase than the wild type which may explain the resistance against chlorate. After growth with thiosulfate they form small amounts of thiosulfate reductase and chlorate reductase C. In crosses between anE.coli Hfrchl + strain and aS.typhimurium chl A strain recombinants were obtained, forming nitrate reductase A and chlorate reductase C. These recombinants do not form gas, which indicates that thechl + gene fromE.coli does not function normally inS.typhimurium.

Thiosulfate reductase isolated from Desulfotomaculum nigrificans.

A thiosulfate reductase from Desulfotomaculum nigrificans has been partially purified by ammonium sulfate fractionation, diethylaminoethylcellulose chromatography, and sucrose density gradient centrifugation. With inner-and outer-labeled (35)S-thiosulfate, the enzyme reduced only the outer sulfur atom to hydrogen sulfide. The enzyme was inhibited by sulfite and also by several sulfhydryl inhibitors. The K(m) value for this enzyme was calculated to be 1.3 x 10(-1)m. Other inorganic sulfur compounds, such as sulfate, sulfite, tetrathionate, and dithionate, were not reduced by this enzyme.

Sulfur metabolism of Bacillus subtilis.

Abstract Sulfur metabolism in Bacillus subtilis resembles that in Escherichia coli in permitting ready assimilation of sulfur from sulfate, thiosulfate and cystine. B. subtilis differes from E. coli in reactions involving sulfade. Sulfide is toxic to B. subtilis but not to E. coli B. subtilis contains rhodanese (thiosulfate: cyanide sulfur transferase, EC 2.8.1.1), an enzyme capable of reducing thiosulfate to the sulfide level of oxidation, and E. coli does not. Cysteine is toxic for both organisms. In B. subtilis cultures, cysteine toxicity is overcome by a mechanism not involving either desulfhydration or oxidation; a lag period is followed by growth which utilizes the cysteine exclusively as sulfur source. Sulfide, although highly toxic to B. subtilis, is also used a preferred sulfur source when present in sufficiently low concentration. B. subtilis rhodanese has been purified about 70-fold from cell lysates, in which it occurs as a soluble enzyme. Like tha mammalian liver mitochondrial rhodanese, it possesses both sulfur transferase and thiosulfate reductase activities which are not assayable through the intact membrane.

Repression of the biosynthesis of thiosulfate reductase in Proteus vulgaris by oxygen

The extracts obtained from aerobic cultures ofProteus vulgaris are completely without thiosulfate reductase activity. This phenomenon can be explained by the repression of biosynthesis of the enzyme by oxygen.