Specific gamma-glutamyl transpeptidase inhibitor from human and animal intestines.

An inhibitor of gamma-glutamyl transpeptidase in human and animal intestines was assayed by means of a new method. In mice fed with LSM fodder, accumulation of the inhibitor in the mucous membrane of the small intestine was observed. Purified gamma-glutamyl transpeptidase inhibitor from mouse and human intestines was identified as L-serine. Neither this amino acid nor purifed inhibitor acted on other intestinal peptidases. Presumably, one of the ingredients of LSM feed influences accumulation of the inhibitor, and consequently diminishes absorption of gamma-glutamyl substrates in the intestine.