branched-chain α-keto acid dehydrogenase complex

a multienzyme complex composed of 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring) [EC 1.2.4.4] (more commonly called branched-chain α-keto acid dehydrogenase), dihydrolipoyllysine-residue (2-methylpropanoyl)transferase [EC 2.3.1.168], and dihydrolipoyl dehydrogenase [EC 1.8.1.4], with thiamine pyrophosphate, lipoic acid, NAD⁺, FAD, and coenzyme A as cofactors. The integrated complex catalyzes the oxidative decarboxylation of the keto acid analogues of the branched-chain amino acids leucine, isoleucine, and valine. Deficiency of any enzyme of the complex causes maple syrup urine disease.