Properties of a soluble thiosulfate sulfur transferase (rhodanese) of the marine methanogen Methanosarcina frisia

Abstract: Cell-free extracts of Methanosarcina frisia contain high thiosulfate sulfur transferase (TST) (rhodanese), slight thiosulfate reductase but no thiosulfate: acceptor oxidoreductase activity. Neither adenylylsulfate reductase nor sulfite: acceptor oxidoreductase activity could be detected. TST is an acidic protein with an M _r of 25 000 and was enriched by ion-exchange chromatography and gel filtration. The enzyme has a temperature optimum at 60°C and a pH optimum at pH 11. The K _m values for thiosulfate and cyanide are 0.53 mM and 1.57 mM, respectively. Low concentrations of cysteine, glutathione, dithioerythritol, and dihydrolipoate increase the activity of the enzyme while unphysiological concentrations of these effectors cause a decrease. Sulfite and N -bromosuccinimide inhibit the energy activity extremely.