Polyketide synthase that catalyzes the biosynthesis of the bicyclic aromatic compound 5-methyl-1-naphthoate in the biosynthesis of the antitumor antibiotic azinomycin B. acetyl-CoA + 7 H(+) + 5 malonyl-CoA + 3 NADPH = 5-methyl-1-naphthoate + 5 CO2 + 6 CoA + 4 H2O + 3 NADP(+) Antibiotic biosynthesis.