Component of a biotin-dependent acyl-CoA carboxylase complex. This subunit catalyzes the ATP-dependent carboxylation of the biotin carried by the biotin carboxyl carrier (BCC) domain, resulting in the formation of carboxyl biotin (PubMed:25695631). When associated with the beta1 subunit AccD1, is involved in branched amino-acid catabolism with methylcrotonyl coenzyme A as the substrate (PubMed:25695631). ATP + hydrogencarbonate + N(6)-biotinyl-L-lysyl-[protein] = ADP + H(+) + N(6)-carboxybiotinyl-L-lysyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. Amino-acid degradation; L-leucine degradation. The biotin-dependent acyl-CoA carboxylase complex is composed of AccA1, which contains the biotin carboxylase (BC) and biotin carboxyl carrier protein (BCCP) domains, and AccD1, which contains the carboxyl transferase (CT) domain (PubMed:25695631). The AccA1/AccD1 complex forms a dodecamer (PubMed:25695631).