Meta-Biol

• Pathways

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.