Cholinesterases

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Cholinesterases
Enzyme classification
EC, category 3.1.1.8 esterases
Response type Deacylation
Substrate Acetylcholine + H 2 O
Products Choline + carboxylate
Occurrence
Parent taxon Eukaryotes , bacteria

Cholinesterases ( ChE ) are enzymes that choline - ester columns. In the metabolism of multicellular animals, they are indispensable for the breakdown of these substances, especially acetylcholine , a neurotransmitter . Cholinesterases are also found in plants, fungi and bacteria.

There are two different cholinesterases in animals. In evolutionary terms, acetylcholinesterase was initially formed in the first multicellular cells . Probably through its copy gene ( gene duplication ) then created with the first chordates the pseudocholinesterase , has a broader substrate spectrum. In humans, the enzymes are synthesized in liver cells and released into the blood plasma . There they split acetylcholine , butyrylcholine and other acylcholines or thiocholines.

Laboratory diagnostics

In laboratory diagnostics , the activity of cholinesterases from heparin plasma or serum is measured in order to monitor the progression of liver diseases.

Reference range for measurements at 37 ° C: 4.9 - 12.0 kU / l

In a patient with liver disease, a decrease in cholinesterase means that the synthesis capacity of the liver cells is impaired, i. that is, the liver produces less protein. Because of the long biological half-life of 12-14 days, the cholinesterase activity is often in the reference range in acute liver diseases. The importance lies primarily in the course of chronic hepatitis or liver cirrhosis .

Since there are different genetic variants of this enzyme, which are not all equally active, a cholinesterase deficiency is found in rare cases even in healthy people. This is medically relevant in the case of anesthesia (general anesthesia) in which muscle relaxants with the active ingredient suxamethonium are used. These are broken down more slowly by people with a cholinesterase deficiency (depending on the severity), which can lead to prolonged apnea and inability to move. This can be clarified with the help of the dibucaine number (cholinesterase activity after inhibition with dibucaine ).

See also

literature

  • Neumeister, Besenthal, Liebrich: Clinical guidelines for laboratory diagnostics , Munich / Jena, Urban & Fischer, 2003 ISBN 3-437-22231-7
  • Lothar Thomas: Labor und Diagnose , Frankfurt / Main, TH-Books, 2005 ISBN 3-980-52155-9

Individual evidence

  1. Riov J, Jaffe MJ: Cholinesterases from Plant Tissues: I. Purification and Characterization of a Cholinesterase from Mung Bean Roots . In: Plant Physiol. . 51, No. 3, March 1973, pp. 520-528. PMID 16658363 . PMC 366299 (free full text).
  2. Domenech CE, Garrido MN, Lisa TA: Pseudomonas aeruginosa cholinesterase and phosphorylcholine phosphatase: two enzymes contributing to corneal infection . In: FEMS Microbiol. Lett. . 66, No. 2, August 1991, pp. 131-5. PMID 1657699 .

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