Plasmalogen

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. 

Information concerning the biosynthesis of choline plasmalogen is somewhat limited. Most of the work on the biological formation of plasmalogens has been done on ethanolamine plasmalogen (see below) rather than choline plasmalogen. An exception is the report of Keenan, Brown and Marks (1961), who showed that C -labelled fatty acids are incorporated in both the acyl ester group and the 

An important step was the finding of Kiyasu and Kennedy (1960) that rat liver contains an enzyme that is able to catalyse the formation of choline plasmalogen from CDP-choline and plasmalogenic diglyceride  

The plasmalogenic diglyceride, prepared enzymically by the action of phospholipase C on the choline-containing phospholipid of beef heart, is defined as a D-a,/5-diglyceride in which the ester at the cx -position is replaced by an imsaturated ether. The reaction is catalysed by a choline-phosphotransferase enzyme similar to the phosphorylcholine-glyceride transferase shown to participate in the biosynthesis of lecithin (Reaction 12). A similar reaction occurs in brain (McMurray 1964b). 

It is also known from the work of Sribney and Kennedy (1958) that many tissues contain an enzyme (CDP-choline ceramide cholinephosphotransferase EC 2.7.8.a) capable of transfering phosphorylcholine from CDP-choline to ceramide with the formation of sphingomyelin  

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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. 

The etlranolamine plasmalogens have ethanolamine in place of choline. 

What products would you obtain from hydrolysis of a plasmalogen (Problem 27.16) with aqueous NaOH With H36+ ... 

These compounds constimte as much as 10% of the phospholipids of brain and muscle. StmcmraUy, the plasmalogens resemble phosphatidylethanolamine but possess an ether link on the sn- carbon instead of the ester link found in acylglycerols. Typically, the alkyl radical is an unsamrated alcohol (Figure 14-10). In some instances, choline, serine, or inositol may be sub-stimted for ethanolamine. 

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.

In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels. 

Plasmalogens and platelet-activating factor (PAF) are ether phospholipids formed from dihydroxyacetone phosphate. 

Ethanol and choline glycerolipids were isolated from calf brain and beef heart lipids by PTLC using silica gel H plates. Pure ethanol amine and choline plasmalogens were obtained with a yield of 80% [74]. Four phosphohpid components in the purple membrane (Bacteriorhodopsin) of Halobacterium halobium were isolated and identified by PTLC. Separated phosphohpids were add-hydrolyzed and further analyzed by GC. Silica gel G pates were used to fractionate alkylglycerol according to the number of carbon atoms in the aliphatic moiety [24]. Sterol esters, wax esters, free sterols, and polar lipids in dogskin hpids were separated by PTLC. The fatty acid composition of each group was determined by GC. 

PLANCK EUNCTION GIBBS FREE ENERGY MASSIEU FUNCTION PLANCK S CONSTANT PLASMALOGEN SYNTHASE PLASMANYLETHANOLAMINE A -DESA-TURASE PLASMIN... 

The analysis of essential fatty acids involves hydrolysis of the ester bonds and subsequent formation of the fatty acid methyl esters, which can be separated by gas chromatography (GC) [10]. By accident, the plasmalogens are hydrolysed in the same reaction and the methylation reaction transforms them into dimethylacetals, which appear in the GC run of the fatty acid methyl esters [4]. 

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