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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 correlation between the degree of serum cholinesterase inhibition and the severity of manifestations is pertinent only in the initial stage of acute poisoning and inhibition is greater in repeated exposures, inhibition remains even after recovery from symptoms.
Correlation of succinylcholine duration of action with plasma cholinesterase activity in subjects with the genotypically normal enzyme.
When the inhibitory potential of 1-5 against acetyl cholinesterase and protease were determined, it was revealed that none of these compounds has activity against these enzymes (Table 1).
Cholinesterase inhibitory activity of the test samples was determined by Ellman's microplate assay with modification (Ellman et al.
Hence, profenofos proved to be the most potent inhibitor of cholinesterases (AChE and BuChE) as compared to cabofuran thus appearing to be more toxic for these aquatic animals.
Bradycardia is a contraindication for all cholinesterase inhibitors.
1 percent of the state's 257 tested pesticide handlers red flagged for cholinesterase depressions of at least 20 percent, according to Labor & Industries' 2010 Cholinesterase Monitoring of Pesticide Handlers in Agriculture Final Report.
Donepezil, like other cholinesterase inhibitors, is used to treat early stages of Alzheimer's disease and dementia.
Tacrine (Cognex[TM]) is a centrally acting cholinesterase inhibitor which slows the degradation of acetylcholine in the cerebral cortex.
Cholinesterase inhibitors are among the few drugs used to treat dementia, although their use does not affect the long-term progress of the disease.
The relatively modest benefit of cholinesterase inhibitors--especially given their expense--has raised questions about cost effectiveness.
There is some evidence that certain patients may benefit from higher doses of the cholinesterase inhibitor medications.