- Transaminase
In
biochemistry , a transaminase or an aminotransferase is anenzyme thatcatalyze s a type of reaction between anamino acid and an α-keto acid. Specifically, this reaction (transamination ) involves removing theamino group from 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 theconcentration s of various transaminases in the blood is important in the diagnosing and tracking manydisease s. Transaminases require the coenzymepyridoxal-phosphate , which is converted intopyridoxamine in the first phase of the reaction, when an amino acid is converted into a keto acid. Enzyme-boundpyridoxamine in turn reacts withpyruvate ,oxaloacetate , oralpha-ketoglutarate , givingalanine ,aspartic acid , orglutamic acid , respectively.The presence of
elevated transaminases can 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
oxaloacetate oralpha-ketoglutarate plays 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.References
*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.ee also
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Valproic acid - aGABA transaminase inhibitorExternal links
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