Characterization of a Glyphosate-Tolerant Enzyme from <i>Streptomyces svecius</i>: A Distinct Class of 5-Enolpyruvylshikimate-3-phosphate Synthases

Abstract

Natural and modified versions of the 5-enolpyruvylshikimate-3-phosphate synthase (<i>epsps</i>) gene have been used to confer tolerance to the broad-spectrum herbicide glyphosate in a variety of commercial crops. The most widely utilized trait was obtained from the <i>Agrobacterium tumefaciens</i> strain CP4 and has been commercialized in several glyphosate-tolerant crops. The EPSPS gene products are enzymes that have been divided into three classes based on sequence similarity, sensitivity to glyphosate, and steady-state catalytic parameters. Herein, we describe the informatics-guided identification and biochemical and structural characterization of a novel EPSPS from <i>Streptomyces sviceus</i> (DGT-28 EPSPS). The data suggest DGT-28 EPSPS and other closely related homologues exemplify a distinct new class (Class IV) of EPSPS enzymes that display intrinsic tolerance to high concentrations of glyphosate (<i>K_i</i> ≥ 5000 μM). We further demonstrate that <i>dgt-28 epsps</i>, when transformed into stable plants, provides robust (≥4× field rates) vegetative/reproductive herbicide tolerance and has utility in weed-control systems comparable to that of commercialized events.