The first normal oral mucosa epithelium in which gamma-glutamyl transpeptidase activity has been detected.

A portion of consistently gamma-glutamyl transpeptidase-positive epithelium in the normal oral mucosa of rats is described. This is the first normal oral mucosa epithelium reported to express activity of the transpeptidase. This enzyme has been used as a marker of malignant transformation in tissues such as epidermis and oral mucosa epithelium. Complementary studies of the enzyme-positive portion of oral mucosa and a neighbouring negative portion, suggest that, in this model, expression of gamma-glutamyl transpeptidase is linked to a terminally-differentiated epithelium.