Acyl-CoA ligase; part of the gene cluster that mediates the biosynthesis of azaphilones, a class of fungal metabolites characterized by a highly oxygenated pyrano-quinone bicyclic core and exhibiting a broad range of bioactivities (PubMed:22921072). In the first step, the non-reducing polyketide synthase azaA forms the hexaketide precursor from successive condensations of five malonyl-CoA units, presumably with a simple acetyl-CoA starter unit (PubMed:22921072). The reactive polyketide chain then undergoes a PT-mediated C2-C7 cyclization to afford the aromatic ring and is eventually released as an aldehyde through the R-domain (PubMed:22921072). The putative ketoreductase azaE is proposed to catalyze the reduction of the terminal ketone resulting in the early culture product FK17-P2a (PubMed:22921072). The monooxygenase azaH was demonstrated to be the only enzyme required to convert FK17-P2a to azanigerone E (PubMed:22921072). AzaH first hydroxylates the benzaldehyde intermediate FK17-P2a at C4, which triggers the formation of the pyran-ring to afford azanigerone E (PubMed:22921072). In parallel, the 2,4-dimethylhexanoyl chain is synthesized by the HR-PKS azaB and is proposed to be transferred to the C4-hydroxyl of azanigerone E by the acyltransferase azaD directly from the ACP domain of azaB (PubMed:22921072). Alternatively, the 2,4-dimethyl-hexanoyl chain may be offloaded from the HR-PKS as a carboxylic acid and converted to an acyl-CoA by azaF (PubMed:22921072). The resulting acyl-CoA molecule could then be taken up as a substrate by AzaD to form azanigerone B (PubMed:22921072). To yield the carboxylic acid substituent in azanigerone A, the hydroxypropyl side chain of azanigerone B would need to undergo a C-C oxidative cleavage catalyzed by cytochrome P450 AzaI (PubMed:22921072). AzaI is proposed to act on a vicinal diol that leads to a C-C bond scission either through an alkoxyradical intermediate or a peroxy complex (PubMed:22921072). In the biosynthesis of azanigerone A, azanigerone B first undergoes hydroxylation at C10, possibly catalyzed by one of the two FAD-dependent monooxygenases encoded in the cluster, azaG or azaL, resulting in the vicinal diol azanigerone C (PubMed:22921072). Oxidative cleavage of azanigerone C by azaI would yield the corresponding aldehyde derivative of azanigerone A (PubMed:22921072). Finally, the dehydrogenase azaJ is proposed to convert the aldehyde functional group into the carboxylic acid, completing the conversion from azanigerone B to azanigerone A (PubMed:22921072). Alternatively, the oxidation of aldehyde to carboxylic acid may be catalyzed by the same P450 enzyme azaI via consecutive oxidation or by endogenous alcohol dehydrogenase (PubMed:22921072). Secondary metabolite biosynthesis. Expression is under the control of the azaphilone cluster-specific transcription factor azaR (PubMed:22921072). Belongs to the ATP-dependent AMP-binding enzyme family.