Phosphatide plasmalogens

Phospholipids and similar substances are fractionated into compound classes more according to partition than adsorption effects, in contrast to the separation of non-polar lipids. Alkenyl ether-esters ( plasma-logens ) are usually not entirely separated from the corresponding ether-ester and diester-phosphatides. Phosphatide plasmalogens concentrate in thin-layer chromatograms on the forward edge of the phosphatide spots. 

Plasmalogens are ether glycerophospholipids in which the alkyl moiety is d5-a,/3-unsaturated (Figure 8.10). Common plasmalogen head groups include choline, ethanolamine, and serine. These lipids are referred to as phosphati-dal choline, phosphatidal ethanolamine, and phosphatidal serine. 

Gottfried, E. L. and Rapport, M. M. (1962) The biochemistry of plasmalogens I Isolation and characterization of phosphatidal choline, a pure native plasmalogen, J. Biol. Chem. 237, 329-333. 

Plasmalogens are phospholipids containing an a,P-unsaturated ether at C-1. Phosphatidal choline, the plasmalogen corresponding to phosphatidyl choline, is formed by desaturation of a 1-alkyl precursor. 

Examples include lecithin, cephalin, sphingomyelin, phosphatidic acid, and plasmalogen. Two types of phospholipids exist glycerophospholipid and sphingosyl phosphatide. A synthetic phospholipid, alkylphosphocholine, has been used in biological and therapeutic areas. 

The fatty acid composition of muscle lipids may show quantitative alterations in diseased muscle. Thus lecithin isolated from human dystrophic muscle had an increased amount of oleic but diminished linoleic acid (Tl). Changes have been recorded also in the fatty acid composition of lecithin from denervated muscle (PI). Recently it has been reported (K16) that the fatty acid pattern of muscle phosphatides from patients with the autosomal dominant form of myotonia congenita differed markedly from that of the autosomal recessive form and from the normal. Tani and his co-workers (F7) have made a detailed study of the phospholipids of normal and dystrophic mouse tissues. In normal mice phosphatidylcholine and phosphatidylethanolamine from skeletal and heart muscles had a very high content of 20-22-carbon polyunsaturated acids, in comparison with those for other tissues the most abundant was docosahexaenoic acid. In dystrophic mice there was a sharp decrease in the proportion of docosahexaenoic acid in the phosphoglycerides from skeletal and heart muscles, suggesting the likelihood of important alterations in muscle membranes. Somewhat similar studies have been reported by Owens (05), who also observed a fall in the proportion of docosahexaenoic acid, mainly in the phosphatidylcholine -j- choline plasmalogen fraction. 

The synthesis of ether phosphatidylethanolamines is analogous to that for the formation of the corresponding phosphatidylcholines (Rosenthal, 1975). The iV-methyl-and AW-dimethyl derivatives have been synthesized from their corresponding phosphatidic acids (Aneja et aL, 1970). The formation of AT-acylphosphatidylethanolamines and other analogues is detailed by Slotboom and Bonsen (1970) and that of ethanolamine plasmalogens in Section 7.5.8. 

The most important phosphatides are the lecithins, cephalins, phosphatidylser-ines, and plasmalogens (a phosphatidyl derivative). Their general structures are shown in Table 23.5. 

Under suitable conditions all of the ester (and ether) linkages of a phosphatide can be hydrolyzed. What organic compounds would you expect to obtain from the complete hydrolysis of (see Table 23.5) (a) a lecithin, (b) a cephalin, and (c) a choline-based plasmalogen [Note Pay particular attention to the fate of the o ,/3-unsaturated ether in part (c).]... 

It is now generally agreed that choline plasmalogen (VII) may be represented by the unsaturated ether structure of Rapport and co-workers (Rapport et al. 1957, Rapport and Franzl 1957a), who suggest that the compound be referred to as phosphatidal choline. 

The principal plasmalogen of brain contains ethanolamine rather than choline. The work of Rapport and associates (Rapport et al. 1957, Rapport and Franzl 1957 b) indicates that the structure of this compound is analogous to that previously described for choline plasmalogen, i.e. phosphatidal ethanolamine (X). 

Metabolism of phosphatides in developing rat brain. — II. Labelling of plasmalogens and other alkali-stable lipids from radioactive cytosine nucleotides. J. Neurochem. 11,315— 26 (1964b). 

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