| Utilization of L-cystine by the gamma-glutamyl transpeptidase-gamma-glutamyl cyclotransferase pathway. | |
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MedLine Citation:
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PMID: 237267 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Cystine is a good acceptor of the gamma-glutamyl group of gamma-glutamyl donors in the reaction catalyzed by gamma-glutamyl transpeptidase. The product of the enzymatic reaction and an authentic sample of gamma-glutamylcystine were shown to exhibit identical chromatographic and electrophoretic behaviors; acid hydrolysis gave equimolar amounts of cystine and glutamate. In studies with two gamma-glutamyl donors, apparent Km values in the neighborhood of 0.3 mM were found for L-cystine; these values are not far from the concentrations of L-cystine in mammalian blood plasma. At an amino-acid acceptor concentration of about 0.5 mM, L-cystine is somewhat more active than L-glutamine, and much more active than L-cystein. L-gamma-Glutamyl-L-cystine was found to be a good substrate of gamma-glutamyl cyclotransferase. These observations thus indicate that L-cystine is a very active substrate of the gamma-glutamyl transpeptidase-gamma-glutamyl cyclotransferase pathway. In relation to the hypothesis that the gamma-glutamyl cycle functions in animo-acid transport, it may be significant that glutathione (which is the most abundant intracellular form) is a much better gamma-glutamyl donor than glutathione disulfide, while the predominant extracellular form-cystine-is a much better gamma-glutamyl acceptor substrate than cystein. |
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Authors:
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G A Thompson; A Meister |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Proceedings of the National Academy of Sciences of the United States of America Volume: 72 ISSN: 0027-8424 ISO Abbreviation: Proc. Natl. Acad. Sci. U.S.A. Publication Date: 1975 Jun |
Date Detail:
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Created Date: 1975-09-09 Completed Date: 1975-09-09 Revised Date: 2010-09-02 |
Medline Journal Info:
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Nlm Unique ID: 7505876 Medline TA: Proc Natl Acad Sci U S A Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 1985-8 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Acyltransferases* Animals Brain / enzymology* Catalysis Chromatography, Paper Cysteine Cystine* Dipeptides Electrophoresis, Paper Glutamine Glutathione Kidney / enzymology* Rats Sheep Structure-Activity Relationship gamma-Glutamylcyclotransferase* gamma-Glutamyltransferase* |
| Chemical | |
Reg. No./Substance:
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0/Dipeptides; 52-90-4/Cysteine; 56-85-9/Glutamine; 56-89-3/Cystine; 70-18-8/Glutathione; EC 2.3.-/Acyltransferases; EC 2.3.2.2/gamma-Glutamyltransferase; EC 2.3.2.4/gamma-Glutamylcyclotransferase |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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