gamma-glutamyl transferase Gamma-glutamyl transpeptidase Lab medicine An enzyme that catalyzes the transfer of a γ-glutamyl group from glutathione or γ-glutamyl peptide to another peptide or amino acid; GGT is located on the cell membrane and microsomal fractions and is involved in amino acid transport across cell membranes; GGT is highest in the liver–GGT is the best single screening assay for detecting latent or chronic liver disease–eg, CA; in hepatobiliary diseases, a 10-fold + ↑ in GGT is seen in liver cancer, hepatic metastases, and PBC; a 4-fold + ↑ in GGT is seen in chronic active hepatitis, intrahepatic cholestasis, alcoholic hepatitis, extrahepatic biliary obstruction, and inactive cirrhosis.
gamma-glutamyl transferase An enzyme widely distributed in body tissues and released into the blood when tissue, especially liver tissue, is damaged. Increased levels occur in liver damage from any cause. Measurements can be used as an index of alcohol abuse. Increased blood levels may sometimes occur without liver cell damage.