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). Within this complex, the catalytic function of this enzyme is to accept, and to transfer to coenzyme A, acyl groups that are generated by the branched-chain alpha-keto acid decarboxylase component. (R)-N(6)-dihydrolipoyl-L-lysyl-[protein] + 2-methylpropanoyl-CoA = (R)-N(6)-(S(8)-2-methylpropanoyldihydrolipoyl)-L-lysyl-[protein] + CoA Binds 1 lipoyl cofactor covalently. Forms a 24-polypeptide structural core with octahedral symmetry. Patients with primary biliary cirrhosis (PBC) show autoantibodies against the E2 component of branched-chain alpha-keto acid dehydrogenase complex. PBC is a chronic, progressive cholestatic liver disease characterized by the presence of antimitochondrial autoantibodies in patients serum. It manifests with inflammatory obliteration of intra-hepatic bile duct, leading to liver cell damage and cirrhosis. The disease is caused by variants affecting the gene represented in this entry. Belongs to the 2-oxoacid dehydrogenase family.