Purification and Properties of Thiosulfate Reductase

Thiosulfate reductase was purified to an almost homogeneous state from Desul-fovibrio vulgaris, strain Miyazaki F, by ammonium sulfate precipitation, chromatog-raphy on DEAE-Toyopearl, Ultrogel AcA 34, and hydroxylapatite, and disc elec-trophoresis. The specific activity was increased 580-fold over the crude extract. The molecular weight was determined by gel filtration to be 85,000-89,000, differing from those reported for thiosulfate reductases from other Desulfovibrio strains. The enzyme had no subunit structure. When coupled with hydrogenase and methyl viologen, it stoichiometrically reduced thiosulfate to sulfite and sulfide with con-sumption of hydrogen. It did not reduce sulfite or trithionate. Cytochrome cs was active as an electron donor. More than 0.75 mM thiosulfate inhibited the enzyme activity. o-Phenanthroline and 2,2'-bipyridine inhibited the enzyme and ferrous ion stimulated the reaction. Thiosulfate reductase reduces thiosulfate to sulfide and sulfite in sulfate-reducing bacteria (/). This enzyme was supposed to participate not only in thiosulfate reduction but also in sulfite reduction in this organism in cooperation with sulfite reduc-tase, which forms thiosulfate and trithionate as well as sulfide from sulfite (2). Thiosulfate reduc-tase has been purified from D. vulgaris, strain Hildenborough (i), and from D. gigas (4). Th