title: Improved purification and sulfhydryl analysis of thiosulfate reductase.
abstract: Thiosulfate reductase purified 900-fold from an extract of baker's yeast by a new procedure consisted of three charge-isomeric species, all with catalytic activity. Amino acid analysis of thiosulfate reductase and titrations with 5,5'-dithiobis(2-nitrobenzoate) and iodo[14C]acetate indicated only one cysteine residue per enzyme molecule. Alkylation of this cysteine with either iodoacetate or iodoacetamide did not inactivate the enzyme, indicating that sulfur-sulfur bond cleavage in the thiosulfate substrate does not require an enzymic sulfhydryl group as attacking nucleophile.
mesh_terms: D000478:Alkylation; D000596:Amino Acids / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D004228:Dithionitrobenzoic Acid; D004591:Electrophoresis, Polyacrylamide Gel; D010088:Oxidoreductases / Q000032:analysis / Q000302:isolation & purification*; D050862:Oxidoreductases Acting on Sulfur Group Donors; D013438:Sulfhydryl Compounds / Q000032:analysis*; D013466:Sulfurtransferases; D015003:Yeasts / Q000201:enzymology
chemical_list: D000596:Amino Acids; D013438:Sulfhydryl Compounds; D004228:Dithionitrobenzoic Acid; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; D013466:Sulfurtransferases; C022747:thiosulfate-dithiol sulfurtransferase