Reaction: 2-methylpropanoyl-CoA + enzyme N6-(dihydrolipoyl)lysine = CoA + enzyme N6-(S-[2-methylpropanoyl]dihydrolipoyl)lysine
For diagram of reaction click here.
Glossary: dihydrolipoyl group
Other name(s): dihydrolipoyl transacylase
Systematic name: 2-methylpropanoyl-CoA:enzyme-N6-(dihydrolipoyl)lysine S-(2-methylpropanoyl)transferase
Comments: A multimer (24-mer) of this enzyme forms the core of the multienzyme 3-methyl-2-oxobutanoate dehydrogenase complex, and binds tightly both EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring) and EC 1.8.1.4, dihydrolipoyl dehydrogenase. The lipoyl group of this enzyme is reductively 2-methylpropanoylated by EC 1.2.4.4, and the only observed direction catalysed by EC 2.3.1.168 is that where this 2-methylpropanoyl is passed to coenzyme A. In addition to the 2-methylpropanoyl group, formed when EC 1.2.4.4 acts on the oxoacid that corresponds with valine, this enzyme also transfers the 3-methylbutanoyl and S-2-methylbutanoyl groups, donated to it when EC 1.2.4.4 acts on the oxo acids corresponding with leucine and isoleucine.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 102784-26-9
References:
1. Massey, L.K., Sokatch, J.R. and Conrad, R.S. Branched-chain amino acid catabolism in bacteria. Bacteriol. Rev. 40 (1976) 42-54. [PMID: 773366]
2. Chuang, D.T., Hu, C.C., Ku, L.S., Niu, W.L., Myers, D.E. and Cox R.P. Catalytic and structural properties of the dihydrolipoyl transacylase component of bovine branched-chain α-keto acid dehydrogenase. J. Biol. Chem. 259 (1984) 9277-9284. [PMID: 6746648]
3. Wynn, R.M., Davie, J.R., Zhi, W., Cox, R.P. and Chuang, D.T. In vitro reconstitution of the 24-meric E2 inner core of bovine mitochondrial branched-chain α-keto acid dehydrogenase complex: requirement for chaperonins GroEL and GroES. Biochemistry 33 (1994) 8962-8968. [PMID: 7913832]
4. Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961-1004. [PMID: 10966480]