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1620787 
Technical Report 
Can allosteric effectors of acetylcholinesterase control the rate of aging of the phosphonylated enzyme? 
Crone, HD 
1974 
PESTAB/75/0351 
Pharmacol 
2 
PESTAB. The effects of some quaternary nitrogen compounds on the rate of aging of sarin-inhibited acetylcholinesterase (AChE) were studied. Aging is the process whereby the reactivation of organophosphorus-inhibited AChE by pyridinium aldoximes diminishes with time. All of the aging experiments exhibited first order kinetics over the period of observation. Increasing the ionic strength slowed the aging process in bovine erythrocyte AChE. At low ionic strength, gallamine triethiodide, tubocurarine, and alcuronium reduced the rate of aging; alcuronium was most effective. At higher ionic strength, none of these compounds altered the rate of aging. However, when the enzyme was present in the cell membrane in its normal position, it was still influenced by tubocurarine and alcuronium, but not by gallamine. 3-Chloro-4-methyl-7-hydroxycoumarin had no effect on aging nor did atropine or its quaternary derivative N-methylatropinium nitrate. Aging was inhibited by a high concentration of N-methylpyridinium iodide. Thus, curariform drugs bind to AChE at low ionic strength, causing a reduction in aging (i. e. , a reduction in the rate of loss of the isopropyl group from the phosphonylated enzyme). The disappearance of the effect at high ionic strength is presumably due to a decrease in the affinity of the compound for the enzyme.