The 2-oxoglutarate dehydrogenase complex catalyzes the overall conversion of 2-oxoglutarate to succinyl-CoA and CO(2). It contains multiple copies of three enzymatic components: 2-oxoglutarate dehydrogenase (E1), dihydrolipoamide succinyltransferase (E2) and lipoamide dehydrogenase (E3). (R)-N(6)-lipoyl-L-lysyl-[dihydrolipoyllysine-residue succinyltransferase] + 2-oxoglutarate + H(+) = (R)-N(6)-(S(8)-succinyldihydrolipoyl)-L-lysyl-[dihydrolipoyllysine-residue succinyltransferase] + CO2 Catabolite repressed. Present with 14300 molecules/cell in log phase SD medium. Belongs to the alpha-ketoglutarate dehydrogenase family.