α-ketoglutarate dehydrogenase complex

a multienzyme complex consisting of at least three distinct enzymes: oxoglutarate dehydrogenase (succinyl-transferring) [EC 1.2.4.2] (more commonly called α-ketoglutarate dehydrogenase), dihydrolipoyllysine-residue succinyltransferase [EC 2.3.1.61], and dihydrolipoyl dehydrogenase [EC 1.8.1.4]. The integrated enzyme complex catalyzes the overall reaction α-ketoglutarate + coenzyme A + NAD⁺ = succinyl coenzyme A + NADH + CO₂. Thiamine pyrophosphate, lipoic acid, and FAD are required as cofactors. The reaction is a part of the tricarboxylic acid cycle. (See illustration under cycle.)