Gamma glutamyltransferases

Gamma glutamyltransferases (or gamma GT) are liver enzymes which are measured in medical tests.

The enzymes are composed of two protein sub-units, one light and one heavy, which are derived from the same precursor and separated by being cleaved. The active site of gamma GT is on the light sub-unit.

The purpose of gamma GT is to transfer the gamma-glutamyl group obtained from glutathione onto amino acids, peptides or water. This is an important detoxification function for the body performed by the liver.

Excessive levels of gamma GT is a marker of a liver abnormality often due to chronic alcohol abuse although it may also be caused by cirrhosis, tumour, hepatitis or cancer.