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The below mentioned article provides a short note on Aminotransferases.
Aminotransferases catalyse the transfer of amino group from an amino acid to a keto acid—a new amino and keto acid are formed in this process. Clinically, the two most important aminotransferases are: Glutamic oxaloacetic transaminase (GOT), now designated aspartate aminotransferase and glutamic pyruvic transaminase (GPT), now designated alanine aminotransferase.
These enzymes are widely distributed in tissues and are normally present also in the blood serum in concentrations up to 19 U/I or, up to 40 Karmen units/dL.
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Aminotransferase activity is increased in certain diseases involving tissues like liver and myocardium owing to the liberation of abnormally large amounts of it from the damaged tissues. Serum amino transferase activity is increased in inflammatory, degenerative, and neoplastic lesions of the liver.
The extent of increase depends on the severity of the disease. The highest values have been obtained in acute hepatic necrosis. Lower values (<250U/I) are obtained in uncomplicated portal cirrhosis, biliary cirrhosis and extra hepatic biliary obstruction as well as in hepatic malignancy (primary or metastatic).
Serum GOT activity is increased in acute heart failure; the values are usually below 100 U/I, but occasionally as high as 1,500 U/I. Slight or moderate increases may occur after intra cardiac operations. In acute myocardial infarction, GOT activity is significantly increased but no increase in GPT.
The determination of GOT is diagnostically important for the following circumstances:
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1. Differentiation between acute myocardial infarction and coronary insufficiency. No increase occurs in coronary insufficiency.
2. Diagnosis of acute myocardial infarction when the ECG changes are not definitive or are difficult to interprete because of previous infarction.
3. Diagnosis of extension of the original infarction or of recurring acute infarction.
Serum GOT may increase in muscular dystrophies, myositis and gangrene. An increase may occur in patients with acute pancreatitis, leukemia and toxemia of pregnancy. No increase in serum GOT occurs in muscular diseases of nervous origin. Increases occur in patients with acute hemolytic anemia and in normal person after prolonged severe exercise. Erythromycin can cause an increase in serum GOT.
Isoenzymes:
GOT exists in two isomeric forms which can be demonstrated by electrophoresis. One is derived from cytoplasm and the other from mitochondria. If the isoenzyme from mitochondria appears in serum, cell death occurs. This indicates a severe lesion and affects the prognosis.
