BCAT_beta_family: Branched-chain aminotransferase catalyses the transamination of the branched-chain amino acids leusine, 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 catalyze the reaction. It has been found that mammals have two foms of the enzyme - mitochondrial and cytosolic forms while bacteria contain only one form of the enzyme. The mitochondrial form plays a significant role in skeletal muscle glutamine and alanine synthesis and in interorgan nitrogen metabolism.Members of this subgroup are widely distributed in all three forms of life.