Glutamyl transpeptidase

Glutamyl Transpeptidase (GGT) is an enzyme that plays a crucial role in the metabolism of glutathione, the body's main antioxidant. It is involved in the transfer of the gamma-glutamyl functional group from glutathione to an acceptor that may be an amino acid, a peptide or water (forming glutamate). This process is essential for the breakdown of glutathione, allowing the antioxidant to be recycled and reused by the body. GGT is found in many tissues, most prominently in the liver, kidneys, and pancreas.

Function

The primary function of GGT is to catalyze the transfer of the gamma-glutamyl group from glutathione to other molecules. This enzymatic activity is critical for the metabolism and recycling of glutathione, facilitating its role in protecting cells from oxidative stress. Additionally, GGT plays a part in the metabolism of leukotrienes and prostaglandins, which are important compounds in the inflammatory response. It also has a role in the absorption and reabsorption of amino acids through the plasma membrane of cells in the renal tubules.

Clinical Significance

Elevated levels of GGT in the blood are often used as a biomarker for liver damage or disease, such as hepatitis, cirrhosis, and liver cancer. It can also indicate bile duct obstruction and other diseases related to the liver or bile ducts. In clinical settings, GGT tests are commonly performed alongside other liver enzyme tests to assess liver health. However, elevated GGT levels can also be found in other conditions, such as pancreatitis, heart failure, and diabetes, making it a non-specific marker that must be interpreted in conjunction with other clinical findings.

Diagnostic Use

The GGT test is a simple blood test that measures the level of glutamyl transpeptidase in the bloodstream. It is often part of a liver panel or comprehensive metabolic panel ordered for individuals showing symptoms of liver disease or for monitoring the liver function of patients on certain medications that can affect the liver. Due to its sensitivity to alcohol, GGT testing is also used to detect chronic alcohol abuse.

Limitations

While the GGT test is valuable for detecting liver disease and bile duct problems, it is not specific to any single condition. Elevated GGT levels can be influenced by factors such as alcohol consumption, medication use, and other medical conditions, necessitating a comprehensive evaluation of test results alongside other diagnostic information.