Mechanism of Rhodanese Catalysis of Thiosulfate-lipoate Oxidation-reduction.

Crystalline beef liver rhodanese (thiosulfate : cyanidesulfurtransferase, EC 2.8.1.1) catalyzes sulfur transfer from SSOato CNby a double displacement mechanism (3, 4). The biological role of this reaction is not clear, but its possible involvement in CNdetoxication has been repeatedly stressed. The present study of the specificity of the crystalline beef liver enzyme and of the occurrence of the enzyme in some common microorganisms has yielded a better understanding of the physiological role of rhodanese. Rhodanese was found to catalyze the reduction of SSOsto HSand SOa” when lipoic acid or lipoamide was used as reducing agent (1). The mechanism of rhodanese-catalyzed SSOareduction was studied, and an intermediate in the reduction was identified as an activated form of sulfide (2).