Evolved Stereoselective Hydrolases for Broad-Spectrum G-Type Nerve Agent Detoxification

A preferred strategy for preventing nerve agents intoxication is catalytic scavenging by enzymes that hydrolyze them before they reach their targets. Using directed evolution, we simultaneously enhanced the activity of a previously described serum paraoxonase 1 (PON1) variant for hydrolysis of the toxic S-P isomers of the most threatening G-type nerve agents. The evolved variants show <= 340-fold increased rates and catalytic efficiencies of 0.2-5 x 10(7) M-1 min(-1). Our selection for prevention of acetylcholinesterase inhibition also resulted in the complete reversion of PON1's stereospecificity, from an enantiomeric ratio (E) < 6.3 x 10(-4) in favor of the R-P isomer of a cyclosarin analog in wild-type PON1, to E > 2,500 for the S-P isomer in an evolved variant. Given their ability to hydrolyze G-agents, these evolved variants may serve as broad-range G-agent prophylactics.