Phosphatidyl choline fatty acid composition

Fatty acid composition of phosphatidyl choline (%) Palmitic acid Stearic acid Eicosapentaenoic acid... 

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. 

Kostetsky, E.Ya., Sanina, N.M. and Naumenko, N.V. (1992). Influence of fatty acid composition on the structure of the thermogram of phosphatidyl choline phase conversion of the sea cucumber, Cucumaria frandatrix (In Russian). Zhumal Evolutsiormoy Biokhimii i Physiologii 28,426-433. 

Sidorov, V.S., Bolgova, O.M., Yarzhombek, A.A. and Lizenko, E.I. (1985). Fatty acid composition of phosphatidyl choline in weak and strong year-old carp at the end of wintering (In Russian). In Biochemistry of Fry of Freshwater fishes , pp. 5-14, Petrozavodsk. 

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. 

However the activation of the A6 desaturation is shown later on. At 15 days it is very important. The apparent Km and Vm of the enz)mie are modified. This activation recovers the double bond index saturated acid ratio to 2.2 and is correlative to an increase of the triacylglycerol phosphatidyl choline ratio of the microsomes. Undoubtedly it is not correlative to the modification of the fatty acid composition of the membrane. Besides Ayala and Brenner have shown that the effect is not due to substrate deprivation (linoleate or a-linolenate) since rats fed on diets containing fish oil during 4 or 6 weeks have even lower A6 desaturation activity in liver microsomes than animals fed on sunflower seed oil compared to rats fed on EFA free diets (Table 2), Therefore the increase of the A6 desaturase activity in EFA deficiency is a physiological response of the cell to maintain the unsaturated/saturated acid ratio and fluidity of the membrane. 

Table 6. Fatty Acid Composition of Phosphatidyl Choline From Photoreceptor Membranes of Rats Raised on Various Diets...

Let us consider first lipid-lipid interaction. Urry et al, showed the existence of a positive CD band at 218 m/x and a negative CD band at about 192 m/z in phosphatidyl choline and phosphatidyl ethanolamine dissolved in trifluoroethanol (86). The 192-m/z band was not characterized in detail, but the 218-m/z band is of such position and shape that the addition of lipid and protein CD bands could produce a composite CD band, and hence an ORD Cotton effect, which is red shifted. As noted by Urry, the 218-m/z CD extremum of lecithin must arise from n — 7T transitions in the fatty acid ester groups. Although the optical activities of solutions of deproteinized membrane phospholipids determined at the same concentration as in the intact membrane are negligibly small, in membranes an ordered array of lipids could greatly enhance rotation. Such an effect could yield information on the nature of lipid-lipid association. This can be tested experimentally. Halobacterium cutirubrum offers a unique system since Kates has shown that the lipids in this extreme halophile contain ether bonds rather than ester bonds (43, 44), Hence, the n — tt transition essential to the CD band at 218 m/z in phospholipids does not exist. Nevertheless, we found that the ORD... 

Glycerophospholipids (PL) are abundant lipid components found in Nature [1]. Most vegetable oils, fish oil and egg yolk are particularly rich in mixtures of phospholipids. They are characterized by the presence of a polar head and two fatty acid chains in the apolar part of the molecule. The two acyl chains mainly consist of saturated fatty acid residues in the snl position and mainly (poly)unsaturated fatty acid chains in the sn2 position. Mixtures of phospholipids at low cost are obtained from the degumming process of vegetable oils. Lecithin, the main component of the mixture, has the polar head characterized by the choline residue. It is usually defined as phosphatidyl choline (PC) and it is understood that the composition of the apolar part is composed of mixtures of fatty acid residues dependent to a large extent on the source of the raw material (fatty acid chains composition of PC from soy beans palmitic 11.6%, stearic 3.4%, oleic 4.6%, linoleic 66.4%, linolenic 8.7%). Scheme 1 shows a PC with two defined acyl chains at the glycerol backbone l-palmitoyl-2-linoleoyl-5n-glycero-3-phosphocholine (PLPC). 

Fig. 2. Changes in the composition of the fatty acids in the a and B positions of liver phosphatidyl choline, induced by different dietary levels of linoleate.

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