Alanine aminotransferase (ALT) is an important enzyme that is primarily involved in amino acid metabolism. This enzyme catalyzes the transfer of an amino group from alanine to α-ketoglutarate, producing pyruvate and glutamate. ALT is found mainly in the liver, where it plays a key role in energy production and nitrogen metabolism. Because ALT is highly concentrated in liver cells, damage to the liver can release this enzyme into the bloodstream. For this reason, ALT is a clinically significant biomarker, and elevated blood levels of ALT are commonly used to detect and monitor liver diseases, including hepatitis, fatty liver disease, and liver injury caused by drugs or alcohol.
 
Signosis' ALT assay kit measures the activity of ALT by detecting its ability to transfer an amino group from L-alanine to alpha-ketoglutarate. This reaction produces pyruvate, which is quantified by another enzyme reaction. Pyruvate is oxidized by pyruvate oxidase to form a pyruvate byproduct and hydrogen peroxide. Then, the pyruvate level, which is proportional to ALT activity in the sample, is determined by quantifying the hydrogen peroxide generated by the enzyme reaction with a fluorogenic probe that can be measured with a spectrophotometer.