TY - JOUR T1 - Human Carboxylesterase 1 Stereoselectively Binds the Nerve Agent Cyclosarin and Spontaneously Hydrolyzes the Nerve Agent Sarin JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.109.062356 SP - mol.109.062356 AU - Andrew C. Hemmert AU - Tamara C. Otto AU - Monika Weirdl AU - Carol C. Edwards AU - Christopher D. Fleming AU - Mary MacDonald AU - John R. Cashman AU - Philip M. Potter AU - Douglas M. Cerasoli AU - Matthew Redinbo Y1 - 2010/01/01 UR - http://molpharm.aspetjournals.org/content/early/2010/01/05/mol.109.062356.abstract N2 - Organophosphorus (OP) nerve agents are potent toxins that inhibit cholinesterases and produce a rapid and lethal cholinergic crisis. Development of protein-based therapeutics is being pursued with the goal of preventing nerve agent toxicity and protecting against the long-term side effects of these agents. The drug-metabolizing enzyme human carboxylesterase 1 (hCE1) is a candidate protein-based therapeutic due to its similarity in structure and function to the cholinesterase targets of nerve agent poisoning. However, the ability of wild-type hCE1 to hydrolyze the G-type nerve agents soman, sarin and cyclosarin has not been determined. We report the crystal structure of hCE1 in complex with the nerve agent cyclosarin. We further employ stereoselective nerve agent analogs to establish that hCE1 exhibits a 1,700- and 2,900-fold preference for the PR enantiomers of analogs of soman and cyclosarin, respectively, and a 5-fold preference for the PS isomer of a sarin analog. Finally, we show that for enzyme inhibited by racemic mixtures of bona fide nerve agents, hCE1 spontaneously reactivates in the presence of sarin but not soman or cyclosarin. Addition of the neutral oxime DAM increases the rate of reactivation of hCE1 from sarin inhibition by more than 60-fold, but has no effect on reactivation with the other agents examined. Taken together, these data demonstrate that hCE1 is only reactivated following inhibition with the more toxic PS isomer of sarin. These results provide important insights toward the long-term goal of designing novel forms of hCE1 to act as protein-based therapeutics for nerve agent detoxification.The American Society for Pharmacology and Experimental Therapeutics ER -