InterPro domain: IPR043132

Aminotransferases share certain mechanistic features with other pyridoxal-phosphate dependent enzymes, such as the covalent binding of the pyridoxal-phosphate group to a lysine residue. On the basis of sequence similarity, these various enzymes can be grouped [ 1 ] into subfamilies.

Branched-chain aminotransferase (BCAT) catalyses the transamination of the branched-chain amino acids leucine, isoleucine and valine to their respective alpha-keto acids, alpha-ketoisocaproate, alpha-keto-beta-methylvalerate and alpha-ketoisovalerate. The enzyme requires pyridoxal 5'-phosphate (PLP) as a cofactor to catalyse the reaction. It has been found that mammals have two forms of the enzyme - mitochondrial and cytosolic forms, while bacteria contain only one form of the enzyme [ 2 ]. BCATs belong to the class 4 type aminotransferases and are widely distributed in many species [ 3 ]. Structurally, BCAT comprises two domains, the small domain consists of 7 beta-strands and 3 alpha-helices, the large domain contains 6 beta-strands and 3 alpha-helices [ 4 ].

This entry represents the C-terminal large domain of BCATs.

1. Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme. J. Bacteriol. 174, 5317-23
2. Human mitochondrial branched chain aminotransferase: structural basis for substrate specificity and role of redox active cysteines. Biochim. Biophys. Acta 1647, 61-5
3. Crystal structures of complexes of the branched-chain aminotransferase from Deinococcus radiodurans with α-ketoisocaproate and L-glutamate suggest the radiation resistance of this enzyme for catalysis. J. Bacteriol. 194, 6206-16