Role of glutamate-199 in the aging of cholinesterase. (Reannouncement with new availability information)
Aging of organophosphate-conjugated acetylcholinesterase results from the loss of an alkoxy group with concomitant stabilization of the conjugate to spontaneous or nucleophile-induced deacylation. We have examined the kinetics of aging in a pinacolylmethylphosphonofluoridate (soman)-inhibited mutant enzyme in which the glutamate (E199) located at the amino-terminal to the active-site sense (S200) was converted to glutamine (Q). For wild type enzyme, the soman-acetylcholinesterase conjugate aged immediately, giving rise to a form of enzyme resistant to reactivation by oximes. In contrast, the E199Q mutant enzyme was largely resistant to aging and could be reactivated by oximes. Since the pH dependence for aging was not altered appreciably, the primary influence of the loss of charge appears to be on the intrinsic rate of aging. The negative charge on E199 likely imparts an inductive effect on the conjugated organophosphate to facilitate removal of the alkoxy group. Cholinesterases, Aging, Organophosphate.
- Research Organization:
- Walter Reed Army Inst. of Research, Washington, DC (United States)
- OSTI ID:
- 210764
- Report Number(s):
- AD-A-274429/0/XAB; TRN: 60640265
- Resource Relation:
- Other Information: PBD: 30 Nov 1993
- Country of Publication:
- United States
- Language:
- English
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