Methylcrotonyl CoA carboxylase (MCCA) catalyzes the reversible reaction of beta-methylglutaconyl-CoA, ADP, orthophosphate, and H2O to form beta-methylcrotonyl-CoA, ATP, and CO2. Active MCCA is composed of two polypeptides, MCCA1 and MCCA2 (Baumgartner et al. 2001; Holzinger et al. 2001). The enzyme has been purified from fibroblast mitochondria. By analogy to the more thoroughly studied bovine homologue, MCCA is thought to be a hexamer of six MCCA1:MCCA2 dimers, and the MCCA1 polypeptides are thought to have biotin moieties covalently bound to a lysine residue at position 681 in the polypeptide chain. Mitochondrial import of MCCA1 and 2 is associated with removal of aminoterminal mitochondrial targeting sequences but the exact lengths of these sequences have not been determined.
Holzinger, A, Röschinger, W, Roscher, AA, Koch, HG, Muntau, AC, Thuy, LP, Nyhan, WL, Lichtner, P, Kattenfeld, T, Lagler, F, Mayerhofer, PU
Baumgartner, ER, Cole, RN, Packman, S, Obie, C, Baumgartner, MR, Suormala, T, Valle, D, Almashanu, S
methylcrotonoyl-CoA carboxylase activity of 6x(Btn-MCCC1:MCCC2) [mitochondrial matrix]
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