The thiosulfate-oxidizing enzyme of Ferrobacillus ferrooxidans (Thiobacillus ferrooxidans)

Abstract

The thiosulfate-oxidizing enzyme tetrathionase was purified about 250-fold from sulfur-grown Ferrobacillus ferrooxidans. It reduced 1 mole of ferricyanide per mole of thiosulfate oxidized, with the production of 0.5 mole of tetrathionate. The pH optimum was 5.0 with acetate buffer, and the Km for thiosulfate was determined to be 9 × 10−4 M. Inhibition studies showed that enzyme activity is not reliant on metal ions or sulfhydryl groups, and no cofactor requirements were found. Tetrathionate was slightly inhibitory to the reaction. A possible role of this enzyme in the oxidation of sulfur and thiosulfate is discussed.