UC Berkeley

Polyketides are a class of natural products known for their chemical complexity and bioactive properties. They are biosynthesized by an assembly line-like system termed polyketide synthases (PKSs), in which each module consists of various enzymatic domains, each of which has a single catalytic function. The polyketide is extended by two carbons and selectively reduced by each module. These biosynthetic principles make PKSs attractive engineering targets, because a simple swap of one enzymatic domain could change the final polyketide structure and effect an improved or novel bioactivity. However, gaping holes in our understanding of polyketide biosynthesis still exist. In particular, the activities of polyketide-associated enzymes remain relatively under-characterized and are generally not the primary focus of engineering efforts. These enzymes, which include glycosyl transferases, cytochrome P450s, and many others, often are responsible for imparting bioactive functional groups into the polyketide backbone or after the assembly of the “naked” polyketide. Many of these non-canonical functional groups discovered within polyketides are therefore the most desirable engineering targets. In this dissertation, I describe my efforts to characterize a family of terminal alkene-forming enzymes which were originally identified in a polyketide biosynthetic cluster. I show that the enzymes are regioselective and that regioselectivity is controlled by a shift in the protein structure. Finally, I show that these enzymes are widespread in not only polyketide biosynthetic gene clusters, but also in other natural product clusters in the genomes of diverse Actinomycetes.