FAD-linked oxidoreductase; part of the cluster B that mediates the biosynthesis of azasperpyranones, members of the azaphilone family that exhibit anti-cancer activities. Azasperpyranones are synthesized by 2 clusters, A and B. Cluster A is responsible for the production of the polyhydric phenol moiety while the azaphilonoid scaffold is produced by the cluster B. The non-reducing polyketide synthase ATEG_03629 produces 5-methyl orsellinic acid, which is then reduced to 5-methyl orsellinic aldehyde by the NRPS-like protein ATEG_03630. 5-methyl orsellinic aldehyde is then first hydroxylated by the FAD-dependent monooxygenase ATEG_03635 and subsequently hydroxylated by the cytochrome P450 monooxygenase ATEG_03631 to produce the unstable polyhydric phenol precursor of azasperpyranones. On the other hand, the polyketide synthase ATEG_07659 is responsible for producing the 3,5-dimethyloctadienone moiety from acetyl-CoA, three malonyl-CoA, and two S-adenosyl methionines (SAM) (Probable). The 3,5-dimethyloctadienone moiety is then loaded onto the SAT domain of ATEG_07661 and extended with four malonyl-CoA and one SAM, which leads to the formation of 2,4-dihydroxy-6-(5,7-dimethyl-2-oxo-trans-3-trans-5-nonadienyl)-3-methylbenzaldehyde (compound 8) after reductive release and aldol condensation (Probable). The FAD-dependent monooxygenase ATEG_07662 is the next enzyme in the biosynthesis sequence and hydroxylates the side chain at the benzylic position of compound 8 (Probable). In Aspergillus nidulans, afoF, the ortholog of the FAD-dependent oxygenase ATEG_07660, is the key enzyme for the biosynthesis of asperfuranone by catalyzing the hydroxylation at C-8 of to prevent the formation of a six-membered ring hemiacetal intermediate and thus facilitatings the formation of a five-membered ring to produce asperfuranone (Probable). In Aspergillus terreus, ATEG_07660 is probably not functional, which leads to the formation of the six-membered ring hemiacetal intermediate presperpyranone instead of asperfuranone (Probable). Finally, ATEG_03636 is involved in the condensation of the polyhydric phenol moiety produced by cluster A and the perasperpyranone precursor produced by cluster B, to yield azasperpyranone A (Probable). Further modifications of azasperpyranone A result in the production of derivatives, including azasperpyranone B to F