The branched-chain alpha-keto dehydrogenase complex catalyzes the overall conversion of alpha-keto acids to acyl-CoA and CO(2). It contains multiple copies of three enzymatic components: branched-chain alpha-keto acid decarboxylase (E1), lipoamide acyltransferase (E2) and lipoamide dehydrogenase (E3) (By similarity). (R)-N(6)-lipoyl-L-lysyl-[dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] + 3-methyl-2-oxobutanoate + H(+) = (R)-N(6)-(S(8)-2-methylpropanoyldihydrolipoyl)-L-lysyl-[dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] + CO2 Heterotetramer of two alpha and two beta chains. Directly associated with ODBA in the E1 complex.