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 γ-glutamyl transpeptidase, the catabolic enzyme of the γ-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 γ-glutamyl transpeptidase activity by serine in a borate buffer partially blocked this accumulation of cystine. Reduced glutathione and oxidazed 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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