What is the full form of AST (Aspartate Aminotransferase)?

AST Full Form

AST stands for Aspartate Aminotransferase (also known as aspartate transaminase), a liver enzyme that catalyzes the reversible transfer of amino groups between aspartate and α-ketoglutarate to produce oxaloacetate and glutamate 1.

Biochemical Characteristics

• AST is a vitamin B6-dependent enzyme that exists in two distinct isoenzyme forms: cytoplasmic AST (c-AST or AST1) and mitochondrial AST (m-AST or AST2) 2, 3
• Both isoforms are homodimers containing a highly conserved lysine-259 residue that binds covalently with the prosthetic group pyridoxal phosphate 3
• The enzyme is located in multiple tissues including liver, heart (myocardium), skeletal muscle, kidney, and red blood cells 2, 3

Clinical Significance

• AST is less liver-specific than ALT because it can be elevated in cardiac muscle injury, skeletal muscle disorders, kidney disease, and red blood cell disorders 4
• In liver disease, AST levels are typically elevated 2-6 times the upper limit of normal in conditions like alcoholic hepatitis, though levels rarely exceed 500 IU/L unless there is concomitant acetaminophen overdose or other acute injury 1
• The AST/ALT ratio provides diagnostic information: a ratio greater than 2 is highly suggestive of alcoholic liver disease, while a ratio less than 1 is more characteristic of nonalcoholic fatty liver disease or viral hepatitis 1, 4

Metabolic Functions

• AST supplies L-aspartate as a substrate for the urea cycle, purine and pyrimidine nucleotide synthesis in the liver, L-arginine synthesis in the kidney, and the purine nucleotide cycle in brain and skeletal muscle 3
• The enzyme participates in the malate-aspartate shuttle in myocardium, gluconeogenesis in liver and kidney, glyceroneogenesis in adipose tissue, and neurotransmitter synthesis in the brain 3
• AST plays a role in glutaminolysis, which is an important metabolic pathway in tumor cells 3

Diagnostic Applications

• AST measurement is widely used as a biomarker for liver and heart damage in clinical laboratories 5
• In hepatic disease, AST isoenzyme determination helps assess liver necrosis, determine prognosis, and identify patients with active alcoholic liver disease 2
• Normal AST ranges differ by sex and are influenced by factors including body mass index and alcohol consumption 1