Aspartate transaminase

Overview
Aspartate transaminase (AST) also called serum glutamic oxaloacetic transaminase (SGOT) or aspartate aminotransferase (ASAT/AAT) is similar to alanine transaminase (ALT) in that it is another enzyme associated with liver parenchymal cells.

Function
It facilitates the conversion of aspartate and alpha-ketoglutarate to oxaloacetate and glutamate.

Isozymes
Two isoenzymes are present in humans. They have high similarity.


 * , the cytosolic isoenzyme derives mainly from red blood cells and heart.
 * , the mitochondrial isoenzyme is predominantly present in liver.

Clinical significance
It is raised in acute liver damage. It is also present in red blood cells and cardiac muscle.

AST was defined as a biochemical marker for the diagnosis of acute myocardial infarction in 1954. However the use of AST for such a diagnosis is now redundant and has been superseded by the cardiac troponins.

AST / ALT is commonly measured clinically as a part of a diagnostic liver function test, to determine liver health. This is because of hepatic deficiency of pyrodoxal-6-phosphate in alcoholics, which is a cofactor for the enzymatic activity of ALT.

Differential Diagnosis of Causes of Elevated AST

 * Acute hepatitis
 * Alcoholic hepatopathy
 * Cholangitis
 * Cholestasis
 * Chronic active hepatitis
 * Cirrhosis
 * Dermatomyositis
 * Drugs
 * Epstein-Barr Virus
 * Fatty liver
 * Hepatic tumor
 * Hypothyroid myopathy
 * Malignant hyperthermia
 * Malignancy
 * Myocardial Infarction
 * Myositis
 * Open heart surgery
 * Perimyocarditis
 * Polymyositis
 * Primary biliary cirrhosis
 * Progressive myodystrophia
 * Pulmonary Embolism
 * Renal infarction
 * Seizure
 * Severe muscle trauma
 * Spasms, muscle injuries
 * Strong physical work