Acetylcholinesterease and Acetylcholine Receptor
1987
Cohen, Saul G.
Our study of acetylcholinesterase (AcChE) is based on the view that the beta-trimethylammonio substituent of acetylcholine binds at an uncharged subsite which is better termed 'trimethyl,' rather than 'anionic,' and would be more specifically explored by uncharged reagents. AcChE was isolated from Torpedo nobiliana; polyacrylamide gel electrophoresis and autoradiography showed satisfactory purity and the major band at 70 kDa. Reversible inhibitors and substrates containing (CH3)3C, (CH3)3Si, CH3S(O2), CH3S(O), CH3S, (CH3)2S+, (CH3)2N+(O-), and C13C substituents were studied. Benzene derivatives bind at an aryl group binding site with energies linear with Hammett rho values, rho +2, and increased by (CH3)2(X) and (CH3)3(X) substituents. tert-Butyl and trimethyl-ammonio groups, binding at the trimethyl site, show strong similar synergism with meta phenolic hydroxyl. Dimethylamino-pyridines bind as strongly as N-methylpyridinium ion. Inactivation of AcChE by styrene oxide, methyl benzene-sulfonate, or 1-bromopinacolone (BrPin) prevents subsequent reaction with 3H- DFP.
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