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标题：Formation of 5-Oxoproline from Glutathione in Erythrocytes by the γ-Glutamyltranspeptidase-Cyclotransferase Pathway
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作者：Anil G. Palekar ; Suresh S. Tate ; Alton Meister 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1974
卷号：71
期号：2
页码：293-297
DOI：10.1073/pnas.71.2.293
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：{gamma}-Glutamyltranspeptidase activity was demonstrated in the membrane fraction of rabbit erythrocytes. The activity observed (with glutathione and various amino-acid acceptors) was similar in magnitude to that of the {gamma}-glutamylcyclotransferase and {gamma}-glutamylcysteine synthetase activities found in the soluble fraction of the cell. No transpeptidase activity was observed with either {gamma}-glutamyl p-nitroanilide or oxidized glutathione in contrast to the rabbit-kidney enzyme for which these compounds and glutathione serve as substrates. Erythrocyte suspensions and hemolysates formed 5-oxoproline (pyroglutamate; pyrrolidone carboxylate); the rate of 5-oxoproline formation from glutathione by hemolysates was increased by addition of methionine. The findings indicate that 5-oxoproline is an end-product of glutathione metabolism in erythrocytes, and that 5-oxoproline passes out of the erythrocyte and is metabolized in other tissues. The observed rate of 5-oxoproline formation is consistent with the conclusion that the {gamma}-glutamyltranspeptidase-cyclotransferase pathway, together with the synthesis of glutathione from glycine, cysteine, and glutamate, account for a large fraction of the observed amino-acid turnover of erythrocyte glutathione.
关键词：pyroglutamate ; pyrrolidone carboxylate ; γ-glutamyl cycle ; γ-glutamyl cyclotransferase