Oxidation of Thiosulfate

The enzyme catalyzing the reaction (4.4) is usually called rhodanese and is thought to occur widely in various organisms. However, as rhodanese requires cyanide of fairly high concentrations (ca. 1 mM) which are not present in normal organisms, the enzyme seems not to occur in Nature. But enzymes occur which have rhodanese activity, e.g., the thiosulfate-cleaving enzyme shows rhodanese activity. Namely, the term rhodanese should not be used as the name of an enzyme, but its use should be limited to the enzymatic activity. 

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Sodium (and potassium) tetrathionate, M2S4O5, can be made by oxidation of thiosulfate by I2 (p. 714) and the free acid liberated (in aqueous solution) by addition of the stoichiometric amount of tartaric acid. 

Breuer, P. L. Jeffrey, M. I. Copper catalysed oxidation of thiosulfate by oxygen in gold leach solutions. Miner. Eng. 2003, 16, 21-30. 

Pedraza, A. M. Villegas, I. Freund, P. L. Chornik, B. Electro oxidation of thiosulfate ion on gold. Study by means of cyclic voltammetry and Auger electron spectroscopy. J Electroanal. Chem. Inter. Electrochem. 1988, 250, 443 149. 

Byerley, J. J. Fouda, S. A. Rempel, G. L. Oxidation of thiosulfate in aqueous ammonia by copper(II) oxygen complexes. Inorg. Nucl. Chem. Lett. 1973, 9, 879-883. 

S.-M. Chen, Electrocatalytic oxidation of thiosulfate by metal hexacyanoferrate film modified electrodes. J. Electroanal. Chem. 417, 145-153 (1996). 

X.Y. Zhou, S.F. Wang, Z.P. Wang, and M. Jiang, Electrocatalytic oxidation of thiosulfate on a modified nickel hexacyanoferrate-film electrode. Fresenius J. Anal. Chem. 345, 424-427 (1993). 

Write a balanced half-reaction that shows the oxidation of thiosulfate ions, 8203 , to sulfite ions, SOs ", in a basic solution. 

Peck then became interested in sulfate-reducing bacteria, which he had got to know in Gest s laboratory. To study the reduction of sulfate. Peck worked in Fritz Lipmann s laboratory in Massachussetts General Hospital (1956) and with Lipmann at Rockefeller University (1957). Lipmann started work on active sulfate in 1954 with Helmut Hilz as a postdoctoral fellow and studied the activation of sulfate to APS and PAPS. Lipmann had left the active sulfate projects by 1957 and started, at Rockefeller University, the studies on protein synthesis. Peck published one paper on the reduction of sulfate with hydrogen in extracts of Desulfovibrio desul-furicans (1959) and one on APS as an intermediate on the oxidation of thiosulfate by Thiobacillus thioparus (1960). 

The original demonstration of APS reductase in T. thioparus used the methylviologen-dependent assay of APS cleavage to AMP and sulfite (Peck 1960), but in the oxidation of thiosulfate the reaction proceeds in the oxidative direction (Eq. 15.4), forming APS. This is the thermodynamically favorable direction of the reaction. Later work showed that APS formation by the reductase could be coupled to the reduction of ferricyanide or to cytochrome c (Peck et al. 1965 Lyric and Suzuki 1970), thereby showing the thermodynamic feasibility of APS as an intermediate in the oxidation pathways for sulhte and thiosulfate. 

The possible roles in sulfur (and sulfide or sulfane-) oxidation of a sulfur dioxygenase or of electron-transport-linked hydration/dehydrogenation are outlined above, but the fate of the sulfite product may be more complex than previously considered. Vishniac and Santer (1957) showed that S-labeled sulfide was rapidly oxidized first to thiosulfate (and polythionates) and then to sulfate by T. thioparus. This observation was incorporated into the original Peck scheme (Eqs. 15.13-15.17) by Peck and Fisher (1962), who realized that the complete oxidation of thiosulfate (after reductive scission to sulfite and sulfide Eq. 15.3) could be explained if there was recycling of sulfide to produce thiosulfate ... 

Peck HD. 1960. Adenosine 5 -phosphosulfate as an intermediate in the oxidation of thiosulfate by Thiobacillus thioparus. Proc Nat Acad Sci USA 46 1053-7. 

Peck HD, Fisher E. 1962. The oxidation of thiosulfate and phosphorylation in extracts of Thiobacillus thioparus. J Biol Chem 237 190-7. 

Starkey RL. 1935. Products of the oxidation of thiosulfate by bacteria in mineral media. J Gen Physiol 18 325 9. 

Vishniac W. 1952. The metabolism of Thiobacillus thioparus. I. The oxidation of thiosulfate. J Bacteriol 64 363-73. 

Babko, A. K., and V. A. Litvinenko Determination of Microamounts of Titanium by Means of the Catalytic Oxidation of Thiosulfate by Hydrogen Peroxide. Zh. Analit. Khim. (Russ.) 21, 302 (1966) J. Anal. Chem. USSR (English Transl.) 21, 267 (1966). 

The bacterium Thiobacillus versutus has been shown to require manganese for both growth and oxidation of thiosulfate. This organism uses a multienzyme system that includes two colorless proteins, A and B, and two c-type cytochromes to oxidize thiosulfate to sulfate. Protein A is a thiosulfate-binding protein protein... 

Schedel, M., and Truper, H. (1980) Anaerobic oxidation of thiosulfate and elemental sulfur in Thiobacillus denitrificans. Arch. Microbiol. 124, 205-210. 

The important oxidation of thiosulfate ion to tetrathionate (S 0 ) has been shown to proceed in an analogous fashion ... 

The oxidation of thiosulfates by hydrogen peroxide proceeds through a series of reactions (Figure 5.9) forming first tetrathionates, then trithionates, then sulfites, and finally sulfates. 

Fiq. 124. Variation of potential in anodic oxidation of thiosulfate (Glasstone and Hickling)... 

A point of view which brings together some of the essential features of both the foregoing theories, d at the same time accounts for many of the facts which these theories fail to explain, is similar to that previously described in connection with the anodic oxidation of thiosulfate. It is suggested that hydroxyl radicals, or hydrogen peroxide formed by their combination in pairs, react with the acetate ions to form acetate radicals, which then combine, possibly with the intermediate formation of acetyl peroxide, to yield ethane and carbon dioxide thus,... 

Oxidation of thiosulfate also produces small amounts of trithionate (SjOl ), tetrathionate (S4OI"), and pentathionate (SsOl ) (Goldhaber and Kaplan 1974). Summarized in Fig. 12.17 are possible oxidation and disproportionation pathways of reduced sulfur species leading toward sulfate that may be mediated by Thiobacilli. (Disproportionation pathways involve no electron transfer see also O Brien and Birkner 1977 Morse et al. 1987.) More recently, Jorgensen (1990) used radioactive to unravel the complex pathways of sulfide oxidation in sediments. He showed that thiosulfate disproportionation to sulfate and sulfide species... 

In Paracoccus vertusus, thiosulfate is oxidized directly to sulfate by the catalysis of an enzyme complex containing several cytochromes c but not cytochrome b (Kelly, 1989). Although sulfite-cytochrome c oxidoreductase occurs in the enzyme complex, the enzyme is thought not to participate in the oxidation of thiosulfate, because the rhodanese activity is not observed with the complex. However, as already indicated, it could be that as the enzyme complex contains a thiosulfatecleaving enzyme strongly bound to both the sulfur-accepting protein and sulfite-cytochrome c oxidoreductase, thiosulfate appears to be oxidized directly to sulfate. 

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