Architecture of modular polyketide synthase in the biosynthesis of bafilomycin A
. Five type Ι PKS genes encodes totally 12 modules responsible for bafilomycin biosynthesis. The first module of BafSI starts the polyketide synthesis from isobutyl group, and extends its length by incorporating 1 acetyl group and 2 propionyl groups, making 9 carbon backbone. The hemiacetal ring can be earlier formed, and further polyketide extension continues until biosynthesis is terminated by thioesterase of the last module of BafSV.