In vitro reconstruction of tetronate RK-682 biosynthesis

Abstract

The tetronate ring appears in several natural products, but the biosynthetic path to this structure has proven elusive. Reconstitution of a polyketide assembly line and in vitro assays with a chemically synthesized intermediate now point to a single enzyme as catalyzing ring formation. The protein phosphatase inhibitor RK-682 is one of a number of potentially valuable tetronate polyketide natural products. Understanding how the tetronate ring is formed has been frustrated by the inaccessibility of the putative substrates. We report the heterologous expression of rk genes in Saccharopolyspora erythraea and reconstitution of the RK-682 pathway using recombinant enzymes, and we show that RkD is the enzyme required for RK-682 formation from acyl carrier protein–bound substrates.