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

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 SP isomers of the most threatening G-type nerve agents. The evolved variants show ≤340-fold increased rates and catalytic efficiencies of 0.2-5 × 107 M−1 min−1. Our selection for prevention of acetylcholinesterase inhibition also resulted in the complete reversion of PON1ʹs stereospecificity, from an enantiomeric ratio (E) < 6.3 × 10−4 in favor of the RP isomer of a cyclosarin analog in wild-type PON1, to E > 2,500 for the SP isomer in an evolved variant. Given their ability to hydrolyze G-agents, these evolved variants may serve as broad-range G-agent prophylactics.