Aspartate transaminase (AST) or aspartate aminotransferase, also known as serum glutamic oxaloacetic transaminase (GOT, SGOT).
It is is a pyridoxal phosphate dependent transaminase enzyme.
It catalyzes the transfer of an α-amino group between aspartate and glutamate and, is an important enzyme in amino acid metabolism.
It is found in the liver, heart, skeletal muscle, kidneys, brain, and red blood cells.
Serum AST level, serum ALT level, and their ratio (AST/ALT ratio) are commonly measured clinically as biomarkers for liver health.
Aspartate transaminase catalyzes the interconversion of aspartate and α-ketoglutarate to oxaloacetate and glutamate.
AST relies on Vitamin B6 as a cofactor to transfer the amino group from aspartate or glutamate to the corresponding ketoacid.
The AST transfer catalyzed by this enzyme is essential in both amino acid degradation and biosynthesis.
Two isoenzymes are present in a wide variety of cells.
GOT1/cAST, the cytosolic isoenzyme derives mainly from red blood cells and heart.
GOT2/mAST, the mitochondrial isoenzyme is present predominantly in liver.
AST has also been found in a number of microorganisms.
AST consists of two identical subunits,
each with approximately 400 amino acid residues and a molecular weight of approximately 45 kD.
AST and alanine transaminase (ALT) enzymes are associated with liver parenchymal cells.
ALT is found predominantly in the liver, with clinically negligible quantities found in the kidneys, heart, and skeletal muscle.
AST is found in the liver, heart muscle, skeletal muscle, kidneys, brain, and red blood cells.
ALT is a more specific indicator of liver inflammation than AST.
AST may be elevated also in diseases: myocardial infarction, acute pancreatitis, acute hemolytic anemia, severe burns, acute renal disease, musculoskeletal diseases, and trauma.
When the AST is higher than ALT, a muscle source of these enzymes should be considered.
Muscle inflammation due to dermatomyositis may cause AST>ALT.
AST and ALT are not good measures of liver functions because they may come from tissues other than liver.
Reference ranges:
Male 8–40 IU/L
Female 6–34 IU/L