Characterization of a phosphodiesterase capable of hydrolyzing EA 2192, the most toxic degradation product of the nerve agent VX.

Glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes is a nonspecific diesterase that enables Escherichia coli to utilize alkyl phosphodiesters, such as diethyl phosphate, as the sole phosphorus source. The catalytic properties of GpdQ were determined, and the best substrate found was bis(p-nitrophenyl) phosphate with a kcat/Km value of 6.7 × 103 M-1 s-1. In addition, the E. aerogenes diesterase was tested as a catalyst for the hydrolysis of a series of phosphonate monoesters which are the hydrolysis products of the highly toxic organophosphonate nerve agents sarin, soman, GF, VX, and rVX. Among the phosphonate monoesters tested, the hydrolysis product of rVX, isobutyl methyl phosphonate, was the best substrate with a kcat/Km value of 33 M-1 s-1. The ability of GpdQ to hydrolyze the phosphonate monoesters provides an alternative selection strategy in the search of enhanced variants of the bacterial phosphotriesterase (PTE) for the hydrolysis of organophosphonate nerve agents. This investigation dem...