IUBMB Enzyme Nomenclature


Accepted name: branched-chain α-keto acid dehydrogenase system

Reaction: 3-methyl-2-oxobutanoate + CoA + NAD+ = 2-methylpropanoyl-CoA + CO2 + NADH

Other name(s): branched-chain α-keto acid dehydrogenase complex; 2-oxoisovalerate dehydrogenase; α-ketoisovalerate dehydrogenase; 2-oxoisovalerate dehydrogenase (acylating)

Systematic name: 3-methyl-2-oxobutanoate:NAD+ 2-oxidoreductase (CoA-methylpropanoylating)

Comments: This enzyme system catalyses the oxidative decarboxylation of branched-chain α-keto acids derived from L-leucine, L-isoleucine, and L-valine to branched-chain acyl-CoAs. It belongs to the 2-oxoacid dehydrogenase system family, which also includes EC, pyruvate dehydrogenase system, EC, 2-oxoglutarate dehydrogenase system, EC, glycine cleavage system, and EC, acetoin dehydrogenase system. With the exception of the glycine cleavage system, which contains 4 components, the 2-oxoacid dehydrogenase systems share a common structure, consisting of three main components, namely a 2-oxoacid dehydrogenase (E1), a dihydrolipoamide acyltransferase (E2), and dihydrolipoamide dehydrogenase (E3). The reaction catalysed by this system is the sum of three activities: EC, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring), EC, dihydrolipoyllysine-residue (2-methylpropanoyl)transferase, and EC, dihydrolipoyl dehydrogenase. The system also acts on (S)-3-methyl-2-oxopentanoate and 4-methyl-2-oxopentanoate.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37211-61-3


1. Namba, Y., Yoshizawa, K., Ejima, A., Hayashi, T. and Kaneda, T. Coenzyme A- and nicotinamide adenine dinucleotide-dependent branched chain α-keto acid dehydrogenase. I. Purification and properties of the enzyme from Bacillus subtilis. J. Biol. Chem. 244 (1969) 4437-4447. [PMID: 4308861]

2. Pettit, F.H., Yeaman, S.J. and Reed, L.J. Purification and characterization of branched chain α-keto acid dehydrogenase complex of bovine kidney. Proc. Natl. Acad. Sci. USA 75 (1978) 4881-4885. [PMID: 283398]

3. Harris, R.A., Hawes, J.W., Popov, K.M., Zhao, Y., Shimomura, Y., Sato, J., Jaskiewicz, J. and Hurley, T.D. Studies on the regulation of the mitochondrial α-ketoacid dehydrogenase complexes and their kinases. Adv. Enzyme Regul. 37 (1997) 271-293. [PMID: 9381974]

4. Evarsson, A., Chuang, J.L., Wynn, R.M., Turley, S., Chuang, D.T. and Hol, W.G. Crystal structure of human branched-chain α-ketoacid dehydrogenase and the molecular basis of multienzyme complex deficiency in maple syrup urine disease. Structure 8 (2000) 277-291. [PMID: 10745006]

5. Reed, L.J. A trail of research from lipoic acid to α-keto acid dehydrogenase complexes. J. Biol. Chem. 276 (2001) 38329-38336. [PMID: 11477096]

[EC created 1972, modified 2019, modified 2020]

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