JBC, Vol. 254, Issue 13, 5573-5575, Jul, 1979
Conversion of glutathione to glutathione disulfide, a catalytic function of gamma-glutamyl transpeptidase
S. S. Tate and J. Orlando
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.