Cholinesterases are enzyme proteins responsible for the breakdown of neurotransmitters, i.e. substances that transmit information between nerve cells. For this reason, they are extremely important for the functioning of the nervous system. The toxic properties of combat gases and insecticides are based on blocking the activity of cholinesterases. These enzymes are mainly produced in the liver. Their concentration in the blood may indicate the he alth and efficiency of this organ. What role do cholinesterases play in the body? What can the results of research on the level of this enzyme show?
Cholinesterasesare differentcholine esterases . The reactions carried out by them serve to deactivate, through decomposition with the use of water, choline esters. Some of the substances they break down act as neurotransmitters in the body. Neurotransmitters are chemicals that are transferred from one nerve cell to another in order to send information.
One of the important reactions catalyzed by cholinesterases is the breakdown of acetylcholine into choline and acetic acid. This substance belongs to the neurotransmitters. The reaction carried out by choline esterases serves to put the cholinergic neuron into a state of rest after an earlier activation.
An example of such a process can be muscle contraction. It is caused by a neurotransmitter, acetylcholine, released in the neuromuscular synapse. If there is a need to relax a muscle, it is necessary to deactivate acetylcholine. Cholinesterases, which hydrolyze this neurotransmitter, are responsible for the course of this reaction.
Ultimately, thanks to the action of these enzymes, the muscle relaxes. Choline is taken up from the synaptic cleft and transported back to the nerve cell. It can be converted back into acetylcholine and then released into the synapse, thereby triggering another muscle contraction.
An enzyme belonging to the group of cholinesterases with high specificity for acetylcholine is acetylcholinesterase.
Cholinesterases - breakdown
There are basically two types of cholinesterases:
- acetylcholinesterases , abbreviatedACHE
- butyrylcholinesterases , abbreviatedBCHE
These two types of cholinesterases differ in their preferences for the reactants they carry out. Acetylcholinesterases hydrolyze acetylcholine faster than other choline esters. Butyrylcholinesterases, on the other hand, show greater selectivity towards butyrylcholine.
Acetylcholinesterase is localized mainly in the blood on the surface of red blood cells and in nerve synapses, including neuromuscular ones.
Butyrylcholinesterases are produced in the liver and are mainly found in the plasma in the body. The half-life of this form of enzyme is 10-14 days. Due to the synthesis of butyrylcholinesterase in the liver, the concentration of this enzyme may be decreased in patients with advanced liver disease.
Cholineesterase inhibitors
Cholinesterase inhibitors are substances that have the ability to block this group of enzymes. Chemicals that are of this nature are neurotoxins. This is due to the fact that they disrupt the nerve transmission in the cholinergic system. Symptoms of poisoning with cholinesterase inhibitors are:
- salivation
- watery eyes
- muscle spasms
- mental disorders
- death
Acetylcholinesterase inhibitors are combat gases such as sarin, soman and tabun. Popular insecticides, classified as organophosphorus or carbamate insecticides, also have this character of action. Direct contact with these substances can be life-threatening.
Acetylcholinesterase is responsible for the relaxation of muscles and organs after contraction caused by acetylcholine released into the synapse. As a result of the action of acetylcholinesterase inhibitors, acetylcholine is not broken down and accumulates in the nerve synapse. This leads to a constant, incessant contraction of the muscles.
Some drugs have the ability to partially and reversibly inhibit cholinesterases. An example is benzodiazepines such as tamazepam. Drugs for the treatment of dementia, such as donepezil and galantamine, also have the nature of acetylcholinesterase inhibitors.
Acetylcholinesterase inhibitors are used to reverse paralysis caused by medical anesthesia. They are also used to treat myasthenia gravis, glaucoma and Alzheimer's disease.
Cholinesterases - application in diagnostics
The level of cholinesterases in the body is used in various types of diagnostic tests.
Amniotic fluid levels of acetocholinesterase during pregnancy: its presence may indicate fetal malformations. Showsneural tube injuries. The result is an indication for further research.
Testing the level of cholinesteraseas a marker of liver efficiency: decreased levels of cholinesterase are observed in severe liver damage. The test is primarily used to diagnose pesticide poisoning and diseases.
Lowering the level of cholinesterases in the blood occurs in the case of:
- cirrhosis of the liver
- hepatitis
- neoplastic disease with liver metastases
- when using hormonal contraception
- with malnutrition
- in chronic heart failure
- in acute myocardial infarction
Sara Janowska, MA in pharmacyPhD student of interdisciplinary doctoral studies in the field of pharmaceutical and biomedical sciences at the Medical University of Lublin and the Institute of Biotechnology in Białystok. A graduate of pharmaceutical studies at the Medical University of Lublin with a specialization in Plant Medicine. She obtained a master's degree defending a thesis in the field of pharmaceutical botany on the antioxidant properties of extracts obtained from twenty species of mosses. Currently, in his research work, he deals with the synthesis of new anti-cancer substances and the study of their properties on cancer cell lines. For two years she worked as a master of pharmacy in an open pharmacy.
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