Bifunctional solanapyrone synthase; part of the gene cluster that mediates the biosynthesis of the phytotoxin solanapyrone, a causal agent of early blight disease of potato and tomato (PubMed:20486243). The prosolanapyrone synthase sol1 is a polyketide synthase that produces the octaketide desmethylprosolanapyrone I via sequential condensations of 7 malonyl-CoA units with one acetyl-CoA unit, and one methylation step (PubMed:20486243). The octaketide backbone is further methylated by the sol2 O-methyltransferase to yield prosolanapyrone I (PubMed:20486243). Prosolanapyrone I is hydroxylated to prosolanapyrone II by the cytochrome P450 monooxygenase sol6 (PubMed:20486243). The solanapyrone synthase sol5 then catalyzes the oxidation of prosolanapyrone II and the subsequent Diels Alder cycloisomerization of the product prosolanapyrone III to solanapyrones A and D (PubMed:9659400, PubMed:18256508). Solanapyrones A and D are then converted into solanapyrones B and E, respectively, by the sol3 dehydrogenase (PubMed:20486243). O2 + prosolanapyrone II = H2O2 + prosolanapyrone III prosolanapyrone III = (-)-solanapyrone A Phytotoxin biosynthesis.