Clinical Significance

The enzyme aspartate aminotransferase (AST) is widely distributed in tissue, primarily in the liver, cardiac muscle, skeletal muscle, kidney, brain and erythrocytes.1 AST catalyzes the transfer of amino groups from L‑aspartate to α‑ketoglutarate, resulting in L‑glutamate and oxaloacetate. This is a critical process of the tricarboxylic acid cycle, in which the coenzyme pyridoxal phosphate (also known as pyridoxal‑5‑phosphate or active vitamin B6) is required. In particular, AST is vital for aerobic glycolysis. AST exists in human tissues as two distinct isoenzymes, one located in the cytoplasm (c‑AST), and the other in mitochondria (m‑AST), which differ in amino acid composition and immunochemical and kinetic properties. In healthy individuals, the circulating AST levels consist mainly of cytoplasmic AST, originating from cytoplasmic leakage, on the other side, mitochondrial AST activity in serum shows a marked increase in patients with extensive liver cell degeneration and necrosis. Although AST activity is important in all cells with high metabolic activity, it is more relevant for liver and muscle cells. 

Primarily, AST is a marker of hepatocellular injury. Measurement of AST activity is therefore used for the diagnosis of hepatic diseases such as acute and chronic viral hepatitis, nonalcoholic fatty liver disease (NAFLD), alcohol‑related liver disease, ischemic hepatopathy, suspected malignant infiltration, cholestasis.3 Although alanine aminotransferase (ALT) is considered a more specific indicator of liver disease, the concentration of AST may be a more sensitive indicator of liver injury in conditions such as alcohol‑related liver disease and in some cases of autoimmune hepatitis.4 Several international guidelines recommend AST testing for monitoring chronic hepatitis status and progression.

_{Source: Roche Cobas ASTP2 Method Sheet Version 1.0 2024-01}