Published Online: 15 APR 2003
Copyright © 2003 by John Wiley & Sons, Inc. All rights reserved.
Encyclopedia of Agrochemicals
How to Cite
Jewess, P. J. 2003. Acetylcholinesterase. Encyclopedia of Agrochemicals. .
- Published Online: 15 APR 2003
Acetylcholinesterase is an enzyme present in the nervous system of all animals and is the site of actions of several important groups of insecticides. It is responsible for catalyzing the hydrolysis of the neurotransmitter acetylcholine on the post-synaptic neural membrane, thus, preventing its continued action. Failure to remove excess acetylcholine results in continued neuronal firing, convulsions, and ultimately death of the organism. Insecticides that inhibit acetylcholinesterase, the organophosphates (OPs), carbamates, carbamoyloximes, and triazamate do so by a mechanism that resembles that of acetylcholine hydrolysis, whereby an acetyl-enzyme intermediate is formed. However, the acyl intermediates formed by the insecticides are much more stable and result in enzymatic inhibition. Mutations in the enzyme that are less susceptible to inhibition by OP and carbamate insecticides have resulted in insecticide-resistant pests.
Acetylcholinesterase is a membrane-bound protein and is covalently anchored to the neuronal membrane. The structure of the enzyme from the electric ray Torpedo californica has shown that the active site, consisting of serine, histidine, and glutamic acid residues, is at the bottom of a deep cleft in the protein. Surprisingly, a tryptophan residue was found to be responsible for binding the quaternary ammonium group of acetylcholine and other cholinergic ligands. The findings have resulted in much research to model and design new compounds that may interact with this important enzyme.