Involved in the biosynthesis of mycolic acids (By similarity). Catalyzes the activation of long-chain fatty acids as acyl-adenylates (acyl-AMP), which are then transferred to the phosphopantetheine arm of the polyketide synthase Pks13 for further chain extension (By similarity). Can use decanoate (C10), dodecanoate (C12) and tetradecanoate (C14) (PubMed:23364516, PubMed:26900152). a long-chain fatty acid + ATP + holo-[ACP] = a long-chain fatty acyl-[ACP] + AMP + diphosphate ATP + decanoate + H(+) = decanoyl-AMP + diphosphate ATP + dodecanoate + H(+) = diphosphate + dodecanoyl-AMP ATP + H(+) + tetradecanoate = diphosphate + tetradecanoyl-AMP The acyl-AMP ligase activity is inhibited by the alkylphosphate ester of AMP, adenosine 50-dodecylphosphate (AMPC12) (PubMed:23364516, PubMed:26900152). Also inhibited by eicosyl-AMP (AMPC20) (PubMed:26900152). kcat is 16.1 min(-1) with decanoate as substrate (PubMed:23364516). kcat is 11.2 min(-1) with dodecanoate as substrate (PubMed:23364516). kcat is 4.2 min(-1) with tetradecanoate as substrate (PubMed:23364516). Optimum pH is 7.5. Lipid metabolism; mycolic acid biosynthesis. Monomer. Consists of two globular domains connected by a flexible linker. ATP binds in a cleft at the interface between the N- and C-terminal domains and its binding induces significant local conformational changes. Belongs to the ATP-dependent AMP-binding enzyme family.