Ether lipids plasmalogens

FIGURE 10-9 Ether lipids. Plasmalogens have an ether-linked alkenyl chain where most glycerophospholipids have an ester-linked fatty acid (compare Fig. 10-8). Platelet-activating factor has a long ether-linked alkyl chain at C-l of glycerol, blit C-2 is ester-linked to acetic acid,... 

Oral bioavailability of the ether lipid plasmalogen precursor, PPl-1011, in the rabbit A new therapeutic strategy for Alzheimer s disease. Lipids Health Dis. 10, 227. 

Figure 24-4. Biosynthesis of ether lipids, including plasmalogens, and platelet-activating factor (PAF). In the de novo pathway for PAF synthesis, acetyl-CoA is incorporated at stage, avoiding the last two steps in the pathway shown here.

Increased plasmalogen levels have not been observed. Erroneously low red cell levels can be encountered when the transmethylation process has not been completed. Breaking the ether lipid bond of the plasmalogens requires more energy than hydrolysis of the fatty acid esters. Evaluation of the plasmalogen levels should not be done after a blood transfusion. Donor erythrocytes will be present for up to 120 days following a transfusion. 

Some animal tissues and some unicellular organisms are rich in ether lipids, in which one of the two acyl chains is attached to glycerol in ether, rather than ester, linkage. The ether-linked chain may be saturated, as in the alkyl ether lipids, or may contain a double bond between C-l and C-2, as in plasmalogens (Fig. 10-9). Vertebrate heart tissue is uniquely enriched in ether lipids about half of the heart phospholipids are plasmalogens. The membranes of halophilic bacteria, ciliated protists, and certain invertebrates also contain high proportions of... 

The biosynthetic pathway to ether lipids, including plasmalogens and the platelet-activating factor... 

Ether phospholipids, analogous to the ether lipids described in Section 2, are also widely distributed. Tire alkenyl ether analogs of phosphatidylcholine (Fig. 8-2) are called plasmalogens.17 In neutrophils the 1-O-alkyl ethers contain the major share of the cell s arachidonic acid, which is esterified in the 2 position.1819... 

Inclusion of other molecules of irregular shape within membranes also lowers Tm. However, a molecule of cholesterol can pack into a bilayer with a cross-sectional area of 0.39 nm2, just equal to that of two hydrocarbon chains.49 It tends to harden membranes above Tm but increases mobility of hydrocarbon chains below Tm.97 -100 A complex of cholesterol and phosphatidylcholine may form a separate phase within the membrane.101102 The ether-linked plasmalogens may account for over 30% of the phosphoglycerides of the white matter of the brain and of heart and ether linked phospholipids are the major lipids of many anaerobic bacteria.103 Their Tm values are a few degrees higher than those of the corresponding acyl phospholipids.104... 

Farooqui A. A. and Horrocks L. A. (2004). Plasmalogens, platelet activating factor, and other ether lipids. In Nicolaou A. and Kokotos G. (eds.), Bioactive Lipids. Oily Press, Bridgwater, England, pp. 107-134. 

Das, A.K., Holmes, R.D., Wilson, G.N., Hajra, A.K. 1992. Dietary ether lipid incorporation into tissue plasmalogens of humans and rodents. Lipids. 27, 401 405. 

Gorgas, K., Teigler, A., Komljenovic, D., Just, W.W. 2006. The ether lipid-deficient mouse tracking down plasmalogen functions. Biochim. Biophys. Acta 1763 1511-1526. 

Plasmalogens see ether lipids (alkoxylipids). Plastoquinones (abbreviation PQ). o... 

Tkn interesting feature of brain tissue is its considerable content of alkyl- and alkenyl-ether linked PLs indeed, to the present authors knowledge, only spermatozoa possess a comparable significant content of ether lipids [11]. These PLs are detectable with sensitivities comparable to those for diacyl PLs, but with characteristic mass differences (—16 amu compared to the corresponding diacyl-PC). The extreme sensitivity of plasmalogens to even traces of acids is the reason why lyso-Upids are always detectable when TLC separation of brain lipids is performed the acidic groups on the TLC plate (normally unmodified silica gel) are sufficient to induce an unwanted hydrolysis of plasmalogens [134, 135]. 

Although considerable attention has been paid to the metabolism and role of PAF in mammalian tissues (Honda et al, 2002), information on the receptor-mediated metabolism and role of plasmalogens is just beginning to emerge (Farooqui and Horrocks, 2001). Ether lipids play important roles in signal transduction processes. In addition, changes in their metabolism and levels are closely associated with many diseases. 

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