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Acetylcholinesterase

1973; Elsevier BV; Volume: 248; Issue: 6 Linguagem: Inglês

10.1016/s0021-9258(19)44214-2

1083-351X

Basil D. Roufogalis, V. Wickson,

Enzyme function and inhibition

Abstract Activation of acetylcholinesterase by divalent cations and some quaternary ammonium compounds is believed to be mediated through allosteric anionic sites. Treatment with N-ethylmaleimide, 5,5'-dithiobis(2-nitrobenzoic acid), and 2,4,6-trinitrobenzenesulfonic acid did not affect either basal catalytic activity or Ca2+ activation of the enzyme. Alkylating agents of the haloethylamine type and the poorly water-soluble carboxyl group reagents, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline and N,N'-dicyclohexylcarbodiimide, inhibited basal catalytic activity as well as Ca2+ activation. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, a water-soluble carbodiimide, almost totally inhibited activation by Ca2+, gallamine triethiode, and tetraethylammonium iodide in about 4 hours at pH 7.4, at a concentration of 2 mm, whereas under these conditions the carbodiimide had little effect on basal catalytic activity. It is concluded that this water-soluble carbodiimide is an an affinity reagent which reacts with carboxyl groups outside the immediate vicinity of the active site. This carboxyl group modification in some way uncouples allosteric effects of ligands from catalytic activity.