Biotin-dependent carboxylases
biotin-dependent carboxylases
Biotin-dependent carboxylases have two distinct enzymatic activities and catalyze their reactions in two steps. First, a biotin carboxylase (BC) component catalyzes the MgATP-dependent carboxylation of the N1′ atom of the biotin cofactor, using bicarbonate as the CO2 donor. Biotin is covalently linked through an amide bond to a lysine side chain in the biotin carboxyl carrier protein (BCCP) component. In the second step of the reaction, a carboxyltransferase (CT) component catalyzes the CO2 transfer from carboxybiotin to the acceptor of the carboxyl group. Depending on the organism and the enzyme, the components can be separate subunits or part of a multi-domain protein.