Acyl-carrier protein (ACP) acetate ligase of the biotin-dependent malonate decarboxylase multienzyme complex (EC 7.2.4.4). Involved in the conversion of the thiol group of the ACP-bound 2'-(5-phosphoribosyl)-3'-dephospho-CoA prosthetic group into its acetyl thioester using the energy from the hydrolysis of ATP. acetate + ATP + holo-[ACP] = acetyl-[ACP] + AMP + diphosphate