Combinatorial biosynthesis of unnatural polyketides using a type III polyketide synthase from Oryza sativa

Abstract

Polyketides are a class of secondary metabolites found in many bacteria and fungi that display broad range biological and pharmacological activities. Biological syntheses of these molecules by type III polyketides synthases are particularly interesting, due to their ability to catalyze the complete synthesis of the polyketide molecule within the active site of the enzyme. Studies have also shown that these enzymes are promiscuous, allowing them to accept various unnatural substrates as starter molecules to generate novel polyketides. In this study, a recombinant chalcone synthase from Oryza sativa (OsCHS) was purified and characterized. Like most other chalcone synthases, OsCHS is able to utilize ρ‐coumaroyl‐CoA as the starter molecule and catalyze the addition of three acetate units to make naringenin. We also further demonstrate that precursor‐directed combinatorial biosynthesis with unnatural substrates and rational engineering of mutant enzymes can be adopted as strategies to alter the product specificity of OsCHS. Coupling these approaches to highthroughput screening methods will allow us to generate and identify novel polyketides with interesting biological activities.