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 (By similarity). Required during sugar starvation and acts under the control of a sugar-sensing mechanism involving Ser/Thr kinases and phosphatases. (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. Expressed in the non-photosynthetic organs such as siliques, flowers and roots. Barely detected in non senescent green leaves, accumulated slightly at the early stage of leaf senescence and strongly expressed at the late stage of leaf senescence. By dark treatment (at the protein level). Induced by the calmodulin antagonists trifluoperazine and fluphenazine in darkness. Down-regulated by sucrose in a hexokinase dependent manner (at protein level). Up-regulated by Leucine and its derivative alpha-keto acid (KIC). Belongs to the 2-oxoacid dehydrogenase family.