This multifunctional enzyme is a polyketide synthase. It catalyzes a total of 11 steps by seven different component enzymes, in the biosynthesis of the antibiotic patulin. acetyl-CoA + 3 H(+) + 3 malonyl-CoA + NADPH = 6-methylsalicylate + 3 CO2 + 4 CoA + H2O + NADP(+) Mycotoxin biosynthesis; patulin biosynthesis. Homomultimer. In the late logarithmic growth phase.