MUTANT ACETYLCHOLINESTERASES AS POTENTIAL DETOXIFICATION AGENTS FOR ORGANOPHOSPHATE POISONING

It has been demonstrated that cholinesterases (ChEs) are an effective mode of pretreatment to prevent organophosphate (OF) toxicity in mice and rhesus monkeys. The efficacy of ChE as a bioscavenger of OP can be enhanced by combining enzyme pretreatment with oxime reactivation, si nce the scavenging capacity extends beyond a stoichiometric ratio of C hE to OF. Aging has proven to be a major barrier to achieving oxime re activation of acetylcholinesterase (AChE) inhibited by the more potent OPs. To further increase the stoichiometry of OP to ChE required, we have sought AChE mutants that are more easily reactivated than wild-ty pe enzyme. Substitution of glutamine for glutamate (E-199) located at the amino-terminal to the active-site serine (Stool in Torpedo AChE ge nerated an enzyme largely resistant to aging. Here we report the effec t of the corresponding mutation on the rate of inhibition, reactivatio n by -pyridinium)-1-(4-carboxyaminopyridinium)-dimethyl ether hydrochl oride (HI-6), and aging of mouse AChE inhibited by C(+)P(-), and C(-)P (-)-epimers of soman. The E-202 to Q mutation decreased the affinity o f soman for AChE, slowed the reactivation of soman-inhibited AChE by H I-6, and decreased the aging of mutant AChE. These effects were more p ronounced with C(-)P(-)-soman than with C(+)P(-)-soman. In vitro detox ification of soman and sarin by wild-type and E(202)Q AChE in the pres ence of 2 mM HI-6 showed that, E(202)Q AChE was 2-3 times more effecti ve in detoxifying soman and sarin than wild type AChE. These studies s how that these recombinant DNA-derived AChEs are a great improvement o ver wild-type AChE as bioscavengers. They can be used to develop effec tive methods for the safe disposal of stored OP nerve agents and poten tial candidates for pre-or post-exposure treatment for OP toxicity. (C ) 1997 Elsevier Science Inc.