Accumulation of cystine from glutathione-cysteine mixed disulfide in cystinotic fibroblasts; blockade by an inhibitor of gamma-glutamyl transpeptidase |
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Authors: | J D Butler S P Spielberg |
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Affiliation: | 1. Section on Human Biochemical and Developmental Genetics, National Institute of Child Health and Human Development, Building 10, Room 8D-53, Bethesda, Maryland 20205, USA |
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Abstract: | Cystinotic and normal skin fibroblasts in tissue culture were treated with varying concentrations of reduced glutathione, oxidized glutathione and glutathione-cysteine mixed disulfide, substrates of gamma-glutamyl transpeptidase, the catabolic enzyme of the gamma-glutamyl cycle. Cystine accumulated more rapidly and to a greater extent from the glutathione-cysteine mixed disulfide in cystinotic than in normal cells. Inhibition of gamma-glutamyl transpeptidase activity by serine in a borate buffer partially blocked this accumulation of cystine. Reduced glutathione and oxidized glutathione have lesser effects on cystine accumulation. Stored cystine in cystinotic tissues may derive in part from glutathione-cysteine mixed disulfide via transpeptidation. |
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