Cholinesterase lyses choline-based esters, several of which serve as neurotransmitters.


Two enzymes catalyze the hydrolysis of cholinergic neurotransmitters, such as breaking acetylcholine into choline and acetic acid.



These enzyme reactions are necessary to allow a cholinergic neuron to return to its resting state after activation. 



The main types of acetylcholinesterase are found mainly in chemical synapses and red blood cell membranes. 



The other type is butyrylcholinesterase is found mainly in the blood plasma.



The two types of cholinesterase are acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE). 


the former hydrolyses acetylcholine more quickly; the latter hydrolyses butyrylcholine more quickly.



Acetylcholinesterase (ACHE), is found primarily in the blood on red blood cell membranes, in neuromuscular junctions, and in other neural synapses. 



Acetylcholinesterase exists in multiple molecular forms, and the majority of AChE occurs as a tetrameric, G4 form with much smaller amounts of a monomeric G1 form.



Butyrylcholinesterase (BCHE), is produced in the liver and found primarily in blood plasma. 



BCHE half-life is approximately 10 to 14 days.



BCHE production is decreased in liver disease, but  the decrease must be greater than 75% before significant prolongation of neuromuscular blockade occurs with succinylcholine.



An absence or mutation of the BCHE enzyme leads to pseudocholinesterase deficiency. 



Pseudocholinesterase deficiency is a silent condition that manifests itself only when people that have the deficiency receive the muscle relaxants succinylcholine or mivacurium during a surgery.



Pseudocholinesterase deficiency may also affect local anaesthetic selection.



The  BCHE enzyme plays an important role in the metabolism of ester-based local anaesthetics, and its deficiency lowers the margin of safety and increases the risk of systemic effects with this type of anaesthetic. 



The plasma BCHE levels are  increased in 90.5% of cases of acute myocardial infarction.



ACHE in the amniotic fluid may be tested in early pregnancy and can confirm several common types of birth defect, including abdominal wall defects and neural tube defects.



BCHE can be used  against nerve gas and other organophosphate poisoning.



Agents that interfere with the action of cholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.



Nerve gases and many substances used in insecticides act by combining with a residue of serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. 



The enzyme acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. 



In the presence of  an acetylcholine esterase inhibitor, acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop.



Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds.



Some benzodiazepines, such as temazepam have an inhibitory effect on cholinesterase.



Cholinesterase levels can be used as an indirect marker of arsenic exposure.



Anticholinesterases are also used for reversing medication induced paralysis during anesthesia; as well as in the treatment of myasthenia gravis, glaucoma, and Alzheimer’s disease. 



Such compounds are used for killing insects.








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