title: Conversion of glutathione to glutathione disulfide, a catalytic function of gamma-glutamyl transpeptidase.
abstract: A purification procedure, based on that previously used for rat kidney gamma-glutamyl transpeptidase, was used for the purification of glutathione oxidase (which converts glutathione to gluthathione disulfide). The two activities co-purified, the ratio of the activities remaining constant through all steps of the isolation procedure. The purified enzyme was separable into 12 isozymic species by isoelectric focusing. All 12 isozymes exhibited a constant ratio of transpeptidase to glutathione oxidase activities, strongly supporting the conclusion that conversion of glutathione to glutathione disulfide is a catalytic function of gamma-glutamyl transpeptidase. Modulation of oxidase activity by inhibitors and acceptor substrates of transpeptidase is discussed in relation to the possible glutathione binding sites involved in gamma-glutamyl transfer and oxidase activities of the enzyme.
mesh_terms: D000818:Animals; D004220:Disulfides; D005978:Glutathione / Q000378:metabolism*; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007668:Kidney / Q000201:enzymology; D051381:Rats; D005723:gamma-Glutamyltransferase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004220:Disulfides; D007527:Isoenzymes; D005723:gamma-Glutamyltransferase; D005978:Glutathione