biochemistry, a transaminase or an aminotransferase is an enzymethat catalyzes a type of reaction between an amino acidand an α-keto acid. Specifically, this reaction ( transamination) involves removing the amino groupfrom the amino acid, leaving behind an α-keto acid, and transferring it to the reactant α-keto acid and converting it into an amino acid. The enzymes are important in the production of various amino acids, and measuring the concentrations of various transaminases in the blood is important in the diagnosing and tracking many diseases. Transaminases require the coenzyme pyridoxal-phosphate, which is converted into pyridoxaminein the first phase of the reaction, when an amino acid is converted into a keto acid. Enzyme-bound pyridoxaminein turn reacts with pyruvate, oxaloacetate, or alpha-ketoglutarate, giving alanine, aspartic acid, or glutamic acid, respectively.
The presence of
elevated transaminasescan be an indicator of liver damage.
Transaminases in amino acid metabolism in animals
Animals must metabolize proteins to amino acids, at the expense of muscle tissue, when blood sugar is low. The preference of liver transaminases for
oxaloacetateor alpha-ketoglutarateplays a key role in funneling nitrogen from amino acid metabolism to Asp and Glu for conversion to urea for excretion of nitrogen. Similarly, in muscles the use of pyruvate for transamination gives Ala, which is carried by the bloodstream to the liver. Here other transaminases regenerate pyruvate, which provides a valuable precursor for gluconeogenesis. This alanine cycle is analogous to the Cori cycle which allows anaerobic metabolism by muscles.
*Ghany, Marc & Hoofnagle, Jay H. (2005). Approach to the Patient With Liver Disease. In Dennis L. Kasper, Anthony S. Fauci, Dan L. Longo, Eugene Braunwald, Stephen L. Hauser, & J. Larry Jameson (Eds.), "Harrison's Principles of Internal Medicine" (16th Edition), pp. 1814–1815. New York: McGraw-Hill.
*Nelson, David L. & Cox, Michael M. (2000). "Lehninger Principles of Biochemistry" (3rd ed.), pp. 628–631, 634, 828–830. New York: Worth Publishers.
Valproic acid- a GABAtransaminase inhibitor
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