Platelet-activating factor
Identifiers
CAS number	74389-68-7
PubChem	108156
MeSH	Platelet+Activating+Factor
Properties
Molecular formula	C26H54NO7P
Molar mass	523.68 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Platelet-activating factor, also known as a PAF, PAF-acether or AGEPC (acetyl-glyceryl-ether-phosphorylcholine) is a potent phospholipid activator and mediator of many leukocyte functions, including platelet aggregation, inflammation, and anaphylaxis.

It is produced in response to specific stimuli by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells.

Contents 1 Chemistry 2 Function 3 History 4 Biosynthesis and degradation 5 Antagonists 6 See also 7 References 8 External links

[edit] Chemistry

Several molecular species of platelet-activating factor have been identified which vary in the length of the O-alkyl side chain.

• Its alkyl group is connected by an ether linkage at the C1 carbon to a sixteen carbon chain.
• The acyl group at the C2 carbon is an acetate unit (as opposed to a fatty acid) whose short length increases the solubility of PAF, allowing it to function as a soluble signal messenger.
• The C3 has a phosphocholine head group, just like standard phosphatidylcholine.

[edit] Function

It is an important mediator of bronchoconstriction.

It causes platelets to aggregate and blood vessels to dilate. Thus it is important to the process of hemostasis. At a concentration of 10^-12 M, PAF causes life threatening inflammation of the airways to induce asthma like symptoms.

Toxins such as fragments of destroyed bacteria induce the synthesis of PAF, which causes a drop in blood pressure and reduced volume of blood pumped by the heart, which leads to shock and maybe death.

[edit] History

It was discovered by French immunologist Jacques Benveniste in the early 1970s.^[1][2] Its structure was elucidated by Constantinos A. Demopoulos in 1979.^[3]

[edit] Biosynthesis and degradation

PAF is biosynthesized from lysophosphatidylcholine (LPC) and acetyl CoA by the enzyme LPC acetyltransferase (LPCAT).

It is degraded (thereby terminating its capacity to act as a signaling molecule) by a group of enzymes called PAF acetylhydrolases (PAFAHs) which are related to phospholipase A2.

[edit] Antagonists

• SM-12502 is a PAF antagonist, which is metabolized in the liver by the enzyme CYP2A6. ^[4]
• Rupatadine is an antihistamine and PAF antagonist used to treat allergies.

[edit] See also

• Platelet-activating factor receptor
• Platelet-derived growth factor

[edit] References

[edit] External links

• Pharmacorama - PAF (Platelet Activating Factor)
• MeSH Platelet+Activating+Factor

v • d • e Lipids: phospholipids Glycerol backbone (Glycerophospholipids/ Phosphoglycerides) Phosphatidyl-: -ethanolamine/cephalin - -choline/lechithin (dipalmitoyl-) - -serine - -glycerol - -inositol (glyco-) Phosphoinositides: PIP (PI(3)P, PI(4)P, PI(5)P) - PIP2 (PI(3,4)P2, PI(3,5)P2, PI(4,5)P2) - PIP3 Cardiolipin Ether lipids: Plasmalogen (Platelet-activating factor) Sphingosine backbone Sphingomyelin

v • d • e Autacoids Kinins Kininogen (MHWK, LHWK) • Bradykinin • Kallidin • Tachykinins • Urotensin-II Others Angiotensin • Eicosanoid • Histamine • Platelet-activating factor • Serotonin

This cell biology article is a stub. You can help Wikipedia by expanding it. v • d • e