Molecular Pharmacology, Vol 4, 121-130, Copyright © 1968 by the American Society for Pharmacology and Experimental Therapeutics

Kinetics of the Carbamylation of Cholinesterase

¹ Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14850

The kinetics of inhibition of acetylcholinesterase by three methylcarbamates was explored, and it was shown that the observations of both short-term and steady-state inhibitions were satisfactorily accounted for if one assumed that a reversible complex was formed prior to carbamylation of the enzyme. New kinetic evidence for the existence of such a complex was also provided. Both the complex formation and the carbamylation steps were inhibited by the substrates acetylthiocholine and 1-naphthyl acetate. The decarbamylation step was not affected by 2-pyridine-aldoxime methiodide. 1-Naphthyl methylcarbamate did not affect a muscle preparation containing acetylcholine receptor.

Note:
ACKNOWLEDGMENTS Grateful thanks are due to Miss Lorraine Gilmour, who performed all the experimental work, and Mr. Sam Rhine, who computerized the data. The carbamates were generously donated by Union Carbide Company (carbaryl); Chemagro Corporation (o-isopropoxyphenyl methylcarbamate), and Hooker Chemical Company (3,5-diisopropylphenyl methylcarbamate). We are greatly indebted to the U.S. Public Health Service for Research Grant GM 07804, which supported this work in part.