Catalyzes the activation of long-chain fatty acids as acyl-adenylates (acyl-AMP), which are then transferred to the multifunctional polyketide synthase PpsA for further chain extension (PubMed:15042094, PubMed:15749014, PubMed:20553505). Catalyzes the adenylation of the long-chain fatty acids eicosanoate (C20) or docosanoate (C22), and potentially the very-long-chain fatty acid lignocerate (C24) (PubMed:15749014, PubMed:20553505). Involved in the biosynthesis of phthiocerol dimycocerosate (DIM A) and phthiodiolone dimycocerosate (DIM B) (PubMed:11279114, PubMed:20553505). a long-chain fatty acid + ATP + holo-[(phenol)carboxyphthiodiolenone synthase] = a long-chain fatty acyl-[(phenol)carboxyphthiodiolenone synthase] + AMP + diphosphate ATP + eicosanoate + holo-[(phenol)carboxyphthiodiolenone synthase] = AMP + diphosphate + icosanoyl-[(phenol)carboxyphthiodiolenone synthase] ATP + docosanoate + holo-[(phenol)carboxyphthiodiolenone synthase] = AMP + diphosphate + docosanoyl-[(phenol)carboxyphthiodiolenone synthase] ATP + dodecanoate + H(+) = diphosphate + dodecanoyl-AMP ATP + H(+) + hexadecanoate = diphosphate + hexadecanoyl-AMP Lipid metabolism; fatty acid biosynthesis. Disruption of the gene abolishes the production of phthiocerol dimycocerosate (DIM) on the cell envelope (PubMed:11279114). Mutant is attenuated in BALB/c mice. Mutant induces less pneumonia and larger delayed-type hypersensitivity (DTH) reactions. It also induces lower but progressive production of IFN-gamma, IL-4 and TNF-alpha (PubMed:15958066). Vaccination with the fadD26 mutant protects against progressive tuberculosis more efficiently than does Bacille Calmette-Guerin (BCG). It suggests that inactivation of DIM synthesis can increase the immunogenicity of live vaccines, and increase their ability to protect against tuberculosis, indicating that fadD26 mutant could be a potential vaccine candidate (PubMed:15958066). A double unmarked sigE fadD26 mutant is more attenuated and more protective than BCG and is also a promising new prime TB vaccine candidate (PubMed:31591165). Belongs to the ATP-dependent AMP-binding enzyme family.