Cholinesterases, distribution specificity

Chole- Relating to the biliary system, cholestasis The failure of the normal bile flow to the intestine, causing cholestatic jaundice, cholinergic Nerve fibres that release ACETYLCHOLINE, cholinesterases Enzymes that hydrolyse choline esters, especially ACETYLCHOLINE of which there are two main forms acetylcholinesterase ( true cholinesterase ) is specific for acetylcholine, rapid in this action, and has a discrete distribution being especially located near cholinergic nerve terminals (and in erythrocytes) butyrylcholinesterase ( pseudo cholinesterase) is less selective and is able to hydrolyse some drugs (e.g. SUCCINYLCHOLINE CHLORIDE). Many drugs are known that inhibit the action of these enzymes. See anticholinesterases. chromatin A protein found in the nucleus which stains with basic dyes. It is used in the study of the behaviour of... 

Cholinesterases are widely distributed throughout the body in both neuronal and non-neuronal tissues. Based largely on substrate specificity, the cholinesterases are subdivided into the acetylcholinesterases (AChEs) (EC... 

It is well established that acetylcholine can be catabolized by both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) these are also known as "true" and "pseudo" cholinesterase, respectively. Such enzymes may be differentiated by their specificity for different choline esters and by their susceptibility to different antagonists. They also differ in their anatomical distribution, with AChE being associated with nervous tissue while BChE is largely found in non-nervous tissue. In the brain there does not seem to be a good correlation between the distribution of cholinergic terminals and the presence of AChE, choline acetyltransferase having been found to be a better marker of such terminals. An assessment of cholinesterase activity can be made by examining red blood cells, which contain only AChE, and plasma. 

Studies by Miller and co-workers show clear differences in the temporal behavior of flies poisoned by OC s and OP s (8 j 9). This occurs despite similar rates of entry and appears to be a fundamental difference in mechanism "not wholly explainable by cholinesterase inhibition" (authors quote)(9). It might be explainable, however, by cholinesterase selectivity. The housefly is known to contain at least nine AChE isozymes that respond quite differently to inhibition by standard OP s (J ). If these isozymes are assigned specifically (one on one) to different neural functions, rather than randomly distributed, then differential shutdown by OP s and OC s is understandable. All that would be required for a different symptomology would be a different sequence of inhibition of the AChE Isozymes. 

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