FAD-dependent monooxygenase; part of the gene cluster that mediates the biosynthesis of oxepinamides, derivatives of anthranilyl-containing tripeptides that share an oxepin ring and a fused pyrimidinone moiety (PubMed:33004788). The nonribosomal peptide synthetase (NRPS) opaA assembles the quinazolinone core with D-Phe incorporation (PubMed:33004788). The first adenylation domain (A1) of opaA loads and activates anthranilic acid whereas the second A domain (A2) is for activating of L-Phe, which is then converted to D-form by the E domain (PubMed:33004788). The third A domain (A3) is responsible for L-Ile activation and the terminal condensation domain C3 for cyclization and releasing the NRPS product protuboxepin K (PubMed:33004788). The cytochrome P450 monooxygenase opaB then catalyzes alone the oxepin ring formation to convert protuboxepin K into protuboxepin A (PubMed:33004788). The flavoenzyme opaC installs subsequently one hydroxyl group at the oxepin ring, accompanied by double bond migration, to form 15-epi-oxepinamide E (PubMed:33004788). The epimerase opaE changes the D-Phe residue back to L-form, leading to oxepinamide E, which is further methylated at the hydroxyl group at C-12 by the O-methyltransferase OpaF to yield oxepinamide F (PubMed:33004788). Secondary metabolite biosynthesis. Abolishes the production of both oxepinamide F and oxepinamide E and leads to the accumulation of protuboxepin A. Belongs to the paxM FAD-dependent monooxygenase family.