Abstract
Acetyl-CoA carboxylase (ACC) is a member of a family of biotin-containing enzymes, along with urea carboxylase, pyruvate carboxylase, methylcrotonyl-CoA carboxylase, methylmalonyl decarboxylase, oxaloacetate decarboxylase and propionyl carboxylase. This family of proteins catalyzes transcarboxylation reactions with the biotin group serving as a mediator in CO2 transfer. ACC catalyzes the formation of malonyl-CoA from HCO3- and acetyl-CoA. It is the first committed step in fatty acid synthesis. The enzyme may have various subunit compositions, ranging from four separate subunits in bacteria to a single peptide in Eukaryota. Enzymes with the same function are frequently polyphyletic. In effort to reconstruct the evolutionary history of ACC in context of other carboxylases, we conducted a phylogenetic analysis of the biotin carboxylase domain and carboxyl transferase domain of those proteins. The resulting phylogenies suggest a complex history of biotin containing enzymes, with multiple domain rearrangements, fusions and possible defusions.