Platelet activating factor
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| Surname | Platelet activating factor | |||||||||||||||
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| Molecular formula | C 26 H 54 NO 7 P. | |||||||||||||||
| Brief description |
colorless solid |
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| Molar mass | 523.68 g mol −1 | |||||||||||||||
| Physical state |
firmly |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Platelet activating factor ( English platelet activating factor ), abbreviated to PAF , is the common name for the phospholipid with the chemical name 1-O-alkyl-2-acetyl- sn -glycero-3-phosphocholine . This substance received the trivial name because it has the ability to trigger platelet aggregation . It was discovered by the French immunologist Jacques Benveniste in 1970 and is the first phospholipid described in the literature with mediating properties. It plays a major role in interaction with blood components and in the vascular system. Platelet activating factor is inactivated by PAF acetyl hydrolase .
synthesis
This phospholipid analog is produced by different cells ( endothelial cells , fibroblasts , leukocytes , macrophages , platelets ). Basically, two enzymatic synthesis routes are known:
- PAF de novo synthesis : In this synthesis, the enzyme phosphocholine transferase transfers a phosphocholine group to the third position of an alkyl acetyl glycerol of membrane lipids .
- PAF remodeling synthesis : This is where the intermediate product lyso-PAF ( 2-lysophospholipids ) leads to PAF synthesis. An activated phospholipase of group A 2 initially causes phospholipids to be hydrolyzed from the cell membrane . The resulting intermediate product ( lyso-PAF ) is then a substrate for an acetyltransferase , which transfers an acetyl group to the free second position of the glycerol . The intermediate product lyso-PAF can also be formed from PAF by the PAF acetyl hydrolase.
Medical importance
In patients with anaphylaxis , the platelet-activating factor is increased and correlates with the severity of the reaction, whereas PAF acetylhydrolase is decreased, especially in fatal peanut allergies . These findings are interpreted to the effect that a reduced inactivation of platelet-activating factor by PAF acetyl hydrolase contributes to the severity of an anaphylactic reaction.
Individual evidence
- ↑ a b c d data sheet β-Acetyl-γ-O-hexadecyl-L-α-phosphatidylcholine hydrate, ≥98% from Sigma-Aldrich , accessed on April 22, 2017 ( PDF ).
- ↑ a b c d e Karen books: Detection of the platelet activating factor (PAF) in the bovine placenta based on the expression of the PAF receptor and the associated PAF acetyl hydrolases . Justus Liebig University, Giessen 2005, p. 13 ff ., urn : nbn: de: hebis: 26-opus-24919 (dissertation).
- ↑ a b Thomas Hunger: The effect of platelet activating factor (PAF) on intracellular calcium concentration and contractility of isolated adult rat cardiomyocytes . Humboldt University, Berlin 2001, p. 4th ff ., urn : nbn: de: kobv: 11-10013765 (dissertation).
- ↑ Peter Vadas, et al .: Platelet-Activating Factor, PAF Acetylhydrolase, and Severe Anaphylaxis . In: N Engl J Med . No. 358 , 2008, p. 28-35 (English, abstract ).