Human erythrocyte gamma-glutamyltransferase in liver diseases.

The gamma-glutamyltransferase activity of erythrocytes was estimated in healthy adults and in patients with hepatobiliary disease. Control activity was 1.97 +/- 0.70 X 10(-4) U/mg ghost protein. Activity was elevated to 8.54 +/- 7.81 X 10(-4) U/mg in patients with hepatobiliary disease. Very high values, above 15 X 10(-4) U/mg were seen in patients with primary and secondary liver carcinoma, and also in some patients with obstructive jaundice. The erythrocyte enzyme had the same kinetic properties as serum and liver enzymes and was inhibited by serine-borate mixture, a specific inhibitor of the enzyme. There was no correlation between the erythrocyte enzyme level and either plasma hydrophobic enzyme level or erythrocyte glutathione content.