branched-chain 2-oxo acid dehydrogenase activity
branched-chain 2-oxo acid dehydrogenase activity
Catalysis of the reaction: N(6)-[(R)-lipoyl]-L-lysyl-[dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] + 3-methyl-2-oxobutanoate + H+ = N(6)-[(R)-S(8)-2-methylpropanoyldihydrolipoyl]-L-lysyl-[dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] + CO2. Also acts on 4-methyl-2-oxopentanoate and (S)-3-methyl-2-oxopentanoate, so that it acts on the 2-oxo acids that derive from the action of transaminases on valine, leucine and isoleucine.