Gamma-glutamyl transferase (GGT) is an important enzyme that is involved in amino acid transport and glutathione metabolism. This enzyme catalyzes the transfer of gamma-glutamyl groups between peptides and amino acids, which plays a key role in maintaining cellular antioxidant defenses. GGT is found primarily in the liver, kidneys, pancreas, and bile ducts. Because GGT is released into the bloodstream during liver or bile duct injury, it is a clinically significant biomarker used to assess liver function and detect hepatobiliary disease. Elevated GGT levels are commonly associated with conditions such as alcohol-related liver disease, bile duct obstruction, hepatitis, and pancreatic disorders.
 
Signosis' GGT assay kit utilizes a chromogenic substrate, γ-glutamyl-p-nitroanilide (GPNA), that releases a colored product when it hydrolyzed into pNA by GGT. The pNA product is yellow and can be measured spectrophotometrically at an absorbance of 405 nm.