The reductive enzymatic cleavage of thiosulfate

Abstract

Methods presently used for the enzymatic assay of the thiosulfate cleaving reaction in bacterial cell-free systems are critically examined. Conditions under which strong acids are used to terminate the reaction and to release H2S proved to be unsuitable. A non-enzymatic production of H2S under such conditions is demonstrated. A reliable procedure for the measurement of H2S production from the enzymatic cleavage of thiosulfate is described. This method was used to measure the thiosulfate cleaving reaction catalyzed by cell-free extracts of phototrophic bacteria of the genusChromatium. As reductants, hydrogen-hydrogenase/methyl viologen system, reduced glutathione or dihydrolipoate were used. The same extract fraction catalyzed the rhodanese reaction.