Platelet-activating factor structure

Platelet-activating factor (structure) is a glycerol ether with potent physiological properties. At concentrations as low as 1 picomolar, it stimulates of blood platelet aggregation, reduction of blood pressure, activation of several white blood cell classes, decreased cardiac output, glycogenolysis, uterine contraction. 

It is possible that nematode-secreted AChEs act on alternative substrates to ACh. We had previously suggested, on the basis of structural similarity, that platelet-activating factor (PAF), a potent phospholipid mediator of inflammation, might represent such an alternative substrate (Blackburn and Selkirk, 1992b) but subsequent studies demonstrated that purified AChEs did not cleave PAF, and the enzyme responsible for this activity in secreted products of N. brasiliensis, PAF acetylhydrolase, was purified and defined as a distinct heterodimeric protein (Grigg et al., 1996). Although an open mind on the subject sould be kept, the strict substrate specificity of the nematode-secreted AChEs suggests that they most likely act on ACh alone. 

R. Saunders, R. Anderson, D. Handley, W. Houlihan, M. Lee, J. Tomesch and C. Winslow, Second International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Gatlinburg, TN, October 26-29 (1986) Abstr. p. 33. 

Platelet activating factor (PAF) is the term used to describe a family of structurally-related lipids that are all acetylated phosphoglycerides (Fig. 

Figure 3.3. Structure of platelet activating factor (PAF). The structure shown is 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine.

Platelet activating factor can be defined as a phosphoglyceride with potent inflammatory properties as well as many other physiological and pathological attributes. The most prevalent chemical form of this factor can be represented by the structural formula shown in Figure 6-1, where n = 15 0, 17 0, 17 1 (in highest amounts). Its chemical name is 1 -0-alkyl-2-acetyl-in-glycero-3-phosphocholine. 

FIGURE 6-1. Chemical structure of platelet activating factor. 

Corey, E. J. Rao, K. S. Enantioselective total synthesis of ginkgolide derivatives lacking the tert-butyl group, an essential structural subunit for antagonism of platelet activating factor. Tetrahedron l tt., 1991, 32 4623-4626. 

Figure 3 The chemical structure of a well-known ether lipid, platelet activating factor, showing stereochemistry. Chemical formula and molecular weight (g/mol) are included.

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