PHYLOGENETIC COMPARISONS OF THE BRANCHED-CHAIN ALPHA-KETOACID DEHYDROGENASE COMPLEX

1. Antibodies against the E(lb) and E2b components of bovine branched-chain alpha-ketoacid (BCKA) dehydrogenase (BCKAD) complex completely inhibited BCKA oxidation in mammalian and avian mitochondria. BCKA oxidation by salmonid mitochondria was less affected and the enzyme from Pseudomonas putida was unaffected. 2. In rodents, anti-E(lb)E2b IgG inhibited oxidation of all three BCKA in a similar dose-dependent manner; oxidation of alpha-ketobutyrate and alpha-keto-gamma-methiolbutyrate was also partially inhibited. 3. Except for the salmonid BCKAD, a similar M(r) for the E2b and E1b-alpha proteins was observed in these species. 4. After digestion with V-8 protease similar immunoreactive peptides were observed for the human and rodent complex.