Inhibition of gamma-glutamyl transpeptidase and induction of glutathionuria by gamma-glutamyl amino acids.

Treatment of mice with various gamma-glutamyl amino acids leads to marked urinary excretion of glutathione and other gamma-glutamyl compounds. There is good correlation between the affinity of gamma-glutamyl transpeptidase for various gamma-glutamyl amino acids and the extent of glutathionuria. The findings indicate that the administered gamma-glutamyl compounds effectively compete with glutathione (exported from kidney cells and present in the glomerular filtrate) for the enzyme. The administration of certain gamma-glutamyl amino acids appears to be a specific and nontoxic procedure for in vivo inhibition of gamma-glutamyl transpeptidase that may be useful in experimental work on glutathione metabolism and function and also for treatment of certain toxicities and for modulation of the metabolism of endogenous glutathione conjugates.