Branched Chain Keto Acid Dehydrogenase E1 Alpha (BCKDHa)

The second major step in the catabolism of the branched-chain amino acids, isoleucine, leucine, and valine, is catalyzed by the branched-chain alpha-keto acid dehydrogenase complex (BCKD), an inner-mitochondrial enzyme complex that consists of 3 catalytic components: a heterotetrameric (alpha2, beta2) branched-chain alpha-keto acid decarboxylase (E1), a homo-24-meric dihydrolipoyl transacylase (E2), and a homodimeric dihydrolipoamide dehydrogenase (E3).

The reaction is irreversible and constitutes the first committed step in BCAA oxidation. The complex also contains 2 regulatory enzymes, a kinase and a phosphorylase. The BCKDHA gene encodes the alpha subunit of E1, and the BCKDHB gene encodes the beta subunit of E1.