[1][2]: 268 GGT plays a key role in the gamma-glutamyl cycle, a pathway for the synthesis and degradation of glutathione as well as drug and xenobiotic detoxification.
[2] GGT is present in the cell membranes of many tissues, including the kidneys, bile duct, pancreas, gallbladder, spleen, heart, brain, and seminal vesicles.
[9] It is also involved in glutathione metabolism by transferring the glutamyl moiety to a variety of acceptor molecules including water, certain L-amino acids, and peptides, leaving the cysteine product to preserve intracellular homeostasis of oxidative stress.
[citation needed] Elevated serum GGT activity can be found in diseases of the liver, biliary system, pancreas and kidneys.
[13][14] Latent elevations in GGT are typically seen in patients with chronic viral hepatitis infections often taking 12 months or more to present.
[17] GGT is elevated by ingestion of large quantities of alcohol (needs reference) However, determination of high levels of total serum GGT activity is not specific to alcohol intoxication,[18] and the measurement of selected serum forms of the enzyme offer more specific information.
[22] GGT elevation has also been occasionally reported following nonsteroidal anti-inflammatory drugs (including aspirin), St. John's wort and kava.