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An enzyme found in blood and in various other tissues that catalyzes hydrolysis of choline esters, including acetylcholine. Abbreviated chE.



any of a group of enzymes of the hydrolase class that act as a catalyst in the hydrolysis of choline esters, according to the equation

(CH3)3N + CH2CH2OCOR + H2O → (CH3)3N+ CH2CH2OH + RCOOH

The cholinesterase of the greatest biological importance is that of the nervous system, acetylcholinesterase (ACE), which acts as a catalyst mainly for the hydrolysis of acetylcholine (R = CH3). Cholinesterases that hydrolyze predominately the esters of choline and other carboxylic acids, such as propionic and butyric acid, have retained the trivial name cholinesterase.

ACE catalyzes the hydrolysis of acetylcholine to acetic acid and choline. Acetylcholine, a highly active substance, is secreted in the synapses of the nervous system and takes part in the transmission of nerve impulses from one nerve cell to the next and from nerve cells to the appropriate organs, such as muscles and endocrine glands. It must be rapidly broken down, however, because accumulations of it block the transmission of nerve impulses and cause paralysis—that is, the loss of nerve functions. For this reason, substances that suppress ACE activity are highly toxic; such substances include organophosphate insecticides, physostigmine, and proserine.

An enzyme with properties similar to those of ACE is found in erythrocytes, but its biological function is not yet known. Less specific cholinesterases are found in blood serum and certain organs and tissues of animals. The most active ACE has been discovered in the electric organs of fish of the suborder Batoidea. Individual cholinesterases of high purity have been obtained from various organs and tissues.

All cholinesterases are proteins with molecular weights ranging from 70,000 to 1,000,000; they contain no coenzymes of low molecular weight. A very important role in the catalytic activity of cholinesterases is played by the amino acids serine, histidine, aspartic acid, and glutamic acid.


References in periodicals archive ?
The determination of cholinesterase inhibition of AChE and BChE were evaluated according to colorimetric Ellman's method (Ellman et al.
In order to understand the binding mechanisms of these compounds with cholinesterase enzymes, MD studies were performed on the most potent inhibitor; angustidine (2) and nauclefine (3).
Contrary to previous findings in a study evaluating 729 European raptors of 20 species, (45) the interspecies analysis did not show a negative correlation between body mass and cholinesterase activity.
45) Male northern cardinals (Cardinalis cardinalis) (7) and Japanese quail (Coturnix japonica) (8) have higher values of cholinesterase 1, another plasma esterase, than their female counterparts.
There are four FDA-approved cholinesterase inhibitors for the treatment of AD: tacrine, donepezil, rivastigmine, and galantamine.
Cholinesterase inhibitory effects of the extracts and compounds of Maclura pomifera (Rafin.
Cholinesterase depression and its association with pesticide exposure across the agricultural season among Latino farmworkers in North Carolina.
Once entering the body, OPs can be enzymatically converted to their oxon form and then react with available cholinesterase.
In summary, although the AMVAC study (AMVAC 1997) was a relatively small study, the analytical methods used for measuring both the dose of dichlorvos and RBC cholinesterase inhibition were state of the art.
The main neurotoxic reaction after absorption of cholinesterase inhibitors is acute cholinergic syndrome due to the inhibition of the acetylcholinesterase (ACHE) enzyme, which is reversible in case of the carbamates and irreversible in case of OPs.
The present study thus reinforces the idea that CPF elicits developmental neurotoxicity through mechanisms independent of, and at doses below the threshold for, cholinesterase inhibition.
Comparative brain cholinesterase inhibiting activity of Glycyrrhiza glabra, Myristica fragrans, ascorbic acid and metrifonate in mice.