Prosolanapyrone-II oxidase (, Sol5, SPS, solanapyrone synthase (bifunctional enzyme: prosolanapyrone II oxidase/prosolanapyrone III cycloisomerase), prosolanapyrone II oxidase) is an enzyme with systematic name prosolanapyrone-II:oxygen 3'-oxidoreductase. This enzyme catalyses the following chemical reaction
This enzyme participates in the biosynthesis of the phytotoxin solanapyrone by some fungi.