Glycerophospholipids choline

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. 

Glycerophospholipids are used for membrane synthesis and for producing a hydrophilic surface layer on lipoproteins such as VLDL. In cell membranes, they also serve as a reservoir of second messengers such as diacylglycerol, inositol 1,4,5-triphosphate, and arachidonic acid. Their structure is similar to triglycerides, except that the last fatty acid is replaced by phosphate and a water-soluble group such as choline (phosphatidylcholine, lecithin) or inositol (phosphatidyl-inositol). 

The simplest of the glycerophospholipids is phosphatidic acid, in which phosphate is linked to the third hydroxyl function, forming a phosphate ester. More complex glycerophospholipids are derivatives of phosphatidic acid in which one of several groups is attached commonly choline, ethanolamine, serine, or myo-inositol. Structures are collected in table 19.1. 

Figure 5.1 The structure of a glycerophospholipid. A simple diagram showing the charges on the head group. In this struction, palmitic and oleic acids, provide the hydrophobic component of the phospholipids and choline (and four bases) and the phosphate group provide the hydrophilic head. The unsaturated fatty acid, oleic acid, provides a kink in the structure and therefore some flexibility in the membrane structure which allows for fluidity. The more unsaturated the fatty acid, the larger is the kink and hence more fluidity in the membrane. Cholesterol molecules can fill the gaps left by the kink and hence reduce flexibility. Hydroxyl groups on the bases marked are those that form phosphoester links. Choline and inositol may sometimes be deficient in the diet so that they are, possibly, essential micronutrients (Chapter 15).

Definition and example of a glycerophospho-lipid Phospholipids that contain glycerol are called glycerophospholipids or phosphoglyc-erides. All contain phosphatidic acid, the simplest glycerophospholipid. When an alcohol, such as choline, is esterified to phosphatidic acid, the product is phosphatidylcholine. 

Cephalins are glycerophospholipids present in foods. They differ from lecithins by having ethanolamine or serine instead of choline in their structure. Could you differentiate between lecithins and cephalins on the basis of the three tests to be performed in this experiment ... 

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). 

Careaga-Houck M, Sprecher H. Effect of a fish oil diet on the composition of rat neutrophils lipids and the molecular species of choline and ethanolamine glycerophospholipids. J Lipid Res 1989 30 237-247. 

Yeo YK. Philbrick DJ, Holub BJ. Altered acyl chain compositions of alkylacyl, alkenylacyl, and diacyl subclasses of choline and ethanolamine glycerophospholipids in rat heart by dietary fish oil. Biochem Biophys Acta 1989 1001 25-30. 

Myocardial ischemia is accompanied by the release of arachidonic acid and the accumulation of lysophosphatidylcholine and lysophosphatidylethanolamine (cf, Corr et al., 1984). Arachidonic acid is predominantly stored in choline- and ethanolamine-glycerophospholipids in myocardium. Thus, these findings demonstrate that phospholipase A2 is activated during myocardial ischemia. Since lyso-phospholipids are potent amphiphilic compounds which have profound effects on the physical propwties of myocardial sarcolemma, the accumulation of these moieties has also been implicated in arrhythmogenesis. 

Choline kinase phosphorylates choline to give a phosphocholine and participates in glycine, serine and threonine metabolism and glycerophospholipid metabolism. Hemicholinium-7 is the prototypical tool compound used to inhibit CHK. Based on inhibitor studies, it has been proposed that CHK is important for the regulation of cell proliferation. Inhibition of choline kinase is also used to target plasmodium and develop novel antimalarials. A series of papers on pyridinium based inhibitors have been published, but no disclosures of more drug-like molecules have been made. 

Figure 1. The structures of two phospholipids. Structure A represents a classic glycerophospholipid, POPC, and it is composed of choline, phosphate, glycerol, and two fatty acids. Structure B is an example of a sphingomyelin, and if is composed of choline, phosphate, sphingosine, and only one fatty acid.

Neural membrane glycerophospholipids are synthesized from three dietary components polyunsaturated fatty acids, uridine monophosphate (UMP), and choline (Farooqui and Horrocks, 2007). Administration of above nutrients increases the level of glycerophospholipids, specific pre- or postsynaptic proteins, and the number of dendritic spines - a requirement for new synapse formation (Wurtman et al., 2009 Kamphnis and Wurtman, 2009). These effects are markedly enhanced when animals receive all three compounds together. This multi-nutrient approach in animals has also been shown to decrease A plaque burden, improve learning and memory through increased cholinergic neurotransmission, and have a neuroprotective effect in several mouse models of AD (Wurtman et al., 2009 ... 

S. Hubbard and S. Brody, Glycerophospholipid Variation in Choline and Inositol Autotrophs of Neurospora Crassa, J. Biol. Chem. 250, 7173-7179 (1975). 

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