Serine and phosphatidyl ethanolamine

In nature, the more common amphiphiles are phospholipids. These are derivatives of glycerol (1,2,3-trihydroxypropane), in which two alcohols form esters with long chain carboxylic acids. The third alcohol forms a phosphate ester, and the phosphate then makes another ester with a simpler alcohol. This creates structures such as phosphatidyl choline, phosphatidyl serine, and phosphatidyl ethanolamine (see next page). The polar group can... 

The technique just described for standards along with specific phospholipid spray tests have been used by Fried and Shapiro (1979) to analyze phospholipids in a parasitic flatworm. Sample preparation employed the Folch et al. (1957) extraction procedure (Experiment 4), and aliquots of sample were spotted essentially as described for standards. The results of that study showed that phosphatidyl choline, phosphatidyl serine, and phosphatidyl ethanolamine were the major phospholipids in the flatworm. Some variation should be expected in phospholipid analysis of animal tissues, although phosphatidyl choline, phosphatidyl serine, and phosphatidyl ethanolamine are usually major phospholipids in animal tissues. The TLC procedure described here following Folch et al. (1957) extraction of tissue should serve as a guide for the TLC analysis of phospholipids in biological materials. 

The phospholipid spray tests should be done along with Experiment 3. The phosphate test will produce very distinct blue spots with the following phospholipids lysophosphatidyl choline, phosphatidyl serine, phosphatidyl choline, and phosphatidyl ethanolamine. The ninhydrin test will produce purple spots only with phosphatidyl serine and phosphatidyl ethanolamine. 

A mixture of phosphatidyl serine and phosphatidyl ethanolamine was once referred to as cephalin. 

La ", by virtue of an ionic radius similar to and a valence higher than Ca., was predicted by Lettvin et al. (1964) to bind at superficially located Ca " adsorption sites in a less reversible manner than does Ca " itself. This work was closely followed by a report on the displacement of Ca " from membranes in the presence of La " (Doggenweiler and Frenk 1965). A differential binding of La by the constituents making up the outer strata of the unit membrane - the lipid polar groups and the nonpolar components - was demonstrated. Lanthanum ions were found to displace Ca from a monolayer of phosphatidyl serine and phosphatidyl ethanolamine but not from phosphatidyl choline. 

Studies by Johnston and Roots (1964), Roots (1968) and Kreps (1981) have revealed an increased ratio between the plasmalogenic and diacyl forms of phosphatidyl ethanolamine in oceanic fish from low-temperature waters. During cold adaptation, the ratios between the main phospholipid fractions alter the relative proportion of phosphatidyl choline decrease and phosphatidyl ethanolamine, phosphatidyl serine and sphingomyelin, all of which contain large amounts of polyenoic acids, increase (Caldwell and Vemberg, 1970 Miller etal, 1976 Wodke, 1978 Hazel, 1979 Brichon et al., 1980 van den Thillart and de Bruin, 1981 Zabelinsky and Shukolyukova, 1989). 

The chemistry of ROS has been studied by several laboratories, and recently reviewed by Daemen (1973). Over 90% of the protein is rhodopsin, a photosensitive glycoprotein of molecular weight around 35,000, which is imbedded in a lipid bilayer. Phospholipids make up about 96% of the lipids of cattle ROS and cholesterol is the major component of the neutral lipid fraction. Phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) are the major phospholipids in all species examined, with phosphatidyl serine (PS), phosphatidyl inositol (PI), and sphingomyelin (SPh) present in lesser amounts (Anderson and Maude, 1972). Detailed analysis of the photoreceptor membranes of vertebrate species ranging from frogs to humans have revealed a fairly constant phospholipid class and protein composition (Basinger and Anderson, unpublished). 

Phosphatidyl Ethanolamines (Cephalins) These glycerophospholipids have previously been named cephalins. However, it is now known that, in addition to phosphatidyl ethanolamine, phosphatidyl serine and phosphatidyl inositol also... 

The work of Hubscher (1962) and Borkenhagen, Kennedy and Fielding (1961) indicates that in mammalian tissues phosphatidyl serine (IX) is not formed by the transfer of (9-phosphoserine from CDP-serine to D-cx,j8-diglyceride by a reaction analogous to those already described for the formation of lecithin and phosphatidyl ethanolamine (Reactions 12 and 19). Apparently free serine and not 0-phosphoserine is the immediate precursor of phosphatidyl serine. Serine displaces ethanolamine from phosphatidyl ethanolamine in an enzymic reaction activated by Ca and not requiring ATP ... 

It is highly hkely that phosphatidyl serine is broken down in animal tissues by a series of reactions similar to those already described for lecithin and phosphatidyl ethanolamine. Both phosphalipase A (Long and Penny 1957) and phospholipase B (Fairbairn 1948) remove fatty acids from serine glycerophosphatides. Also phospholipase C is reported to be inactive (MacFarlane 1948, Zamecnik et al. 1947), whereas phospholipase D degrades phosphatidyl serine into free serine and phosphatidic acid (Kates 1956). 

Ninhydrin 2 g 1 1 in acetone Containing free amino groups Purple spots appear with phosphatidyl ethanolamine and phosphatidyl serine, for instance, after heating at 100°C... 

Phospholipids containing phosphatidyl, inositol, lecithin, serine, and ethanolamine (Stevenson 1986) are the second most abundant identifiable form of organic P in the upper layer of the subsurface. These groups contain glycerol, fatty acids, and phosphate (Sims and Pierzjinski 2005). The P in the structure is a diester, which is more susceptible to degradation in soils than monoesters. 

Figure 3.2 The molecular arrangement of the cell membrane (A) integral proteins (B) glycoprotein (C) pore formed from integral protein (D) various phospholipids with saturated fatty acid chains (E) phospholipids with unsaturated fatty acid chains (F) network proteins (G) cholesterol (H) glycolipid (I) peripheral protein. There are four different phospholipids phosphatidyl serine phosphatidyl choline phosphatidyl ethanolamine and sphingomyelin represented as , o. The stippled area of the protein represents the hydrophobic portion. Source From Ref. 1.

Kreps (1981) and his associates (Akulin et al., 1969 Chebotareva, 1983), in their studies on Far East sockeye salmon, found that the fatty acid composition of lipids in the food influences not only that of the triacyl-glycerols of the fish but also the phospholipid fraction. This comprises, firstly, the phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl serine and, secondly, the sphingomyelin and cardiolipin. All tissues except nervous tissue were found by these workers to be strongly influenced by the composition of the food. However, the fatty acids of the brain have also been found to change according to the diet in European bass (Pagliarani et al., 1986), the proportions of phospholipid to non-phospholipid being unaffected. 

Folch, J. (1942) Brain cephalin, a mixture of phosphatides. Separation from it of phosphatidyl serine, phosphatidyl ethanolamine and a fraction containing an inositol phosphatide, J. Biol. Chem. 146, 35-44. 

The complex lipids in milk fat are comprised of the phosphoglycerides, phosphatidyl choline, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidylinositol and plasmalogens. Also, the non-glyceride phospholipid, sphingomyelin, occurs in important amounts (Jensen, 2002). Bitman and Wood (1990) described the distribution of phospholipid classes in bovine milk and their fatty acid composition. The phospholipids comprise about 1% and cholesterol 0.4—0.5% of the total milk fat. These occur almost completely in the milk fat globule membrane. 

The structural formulas of phosphatidyl choline and the other principal phosphoglycerides—namely, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, and diphosphatidyl glycerol—are given in Figure 12.5. 

Membrane proteins have a unique orientation because they are synthesized and inserted into the membrane in an asymmetric manner. This absolute asymmetry is preserved because membrane proteins do not rotate from one side of the membrane to the other and because membranes are always synthesized by the growth of preexisting membranes. Lipids, too, are asymmetrically distributed as a consequence of their mode of biosynthesis, but this asymmetry is usually not absolute, except for glycolipids. In the red-blood-cell membrane, sphingomyelin and phosphatidyl choline are preferentially located in the outer leaflet of the bilayer, whereas phosphatidyl ethanolamine and phosphatidyl serine are located mainly in the inner leaflet. Large amounts of cholesterol are present in both leaflets. 

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