Phosphatidylcholine, fatty-acid

Jumpsen J, Lien EL, Goh YK, Clandinin MT. 1997. Small changes of dietary (n-6) and (n-3)/fatty acid content ration alter phosphatidylethanolamine and phosphatidylcholine fatty acid composition during development of neuronal and glial cells in rats. J Nutr 127 724-731. 

Another example of ACE analyses of solute-bilayer interactions was described by Roberts et al. (50), who observed retardation of riboflavin by liposomes. Analyses technically similar to liposomal ACE have been performed with mixed bile salt/phosphatidylcholine/fatty acid micelles (95). The partitioning of basic and acidic drugs depended on the acid-base properties of the drug and on the shape and charge of the mixed micelles. 

Fig. 12. r,p-phase diagrams of several phosphatidylcholine/fatty acid(l 2) mixtures dispersed in excess water. 

We also examined the fatty acid composition of several lipid classes in potato leaf tissue. Phosphatidylcholine fatty acid profiles from leaf tissue grown either at 21° C or 6° C from plants in soilless mix are shown n Figure 2. ... 

The seed meal contains simple cynaophoric glucosides (simmondsins) and inositol galactosides (pinitols). Other constituents of the seed meal include phosphatidylcholine fatty acid esters, proteins rich in albumin and globulin (4 1), and polysaccharides that yield xylogalactan oligosaccharides on enzymatic hydrolysis. " ... 

An essential component of cell membranes are the lipids, lecithins, or phosphatidylcholines (PC). The typical ir-a behavior shown in Fig. XV-6 is similar to that for the simple fatty-acid monolayers (see Fig. IV-16) and has been modeled theoretically [36]. Branched hydrocarbons tails tend to expand the mono-layer [38], but generally the phase behavior is described by a fluid-gel transition at the plateau [39] and a semicrystalline phase at low a. As illustrated in Fig. XV-7, the areas of the dense phase may initially be highly branched, but they anneal to a circular shape on recompression [40]. The theoretical evaluation of these shape transitions is discussed in Section IV-4F. 

Fig. 1. Chemical stmcture of phosphatidylcholine (PC) (1) and other related phosphohpids. R C O represents fatty acid residues. The choline fragment may be replaced by other moieties such as ethanolamine (2) to give phosphatidylethanolamine (PE), inositol (3) to give phosphatidylinositol (PI), serine (4), or glycerol (5). IfH replaces choline, the compound is phosphatidic acid (6). The corresponding lUPAC-lUB names ate (1), l,2-diacyl-t -glyceto(3)phosphocholine (2), l,2-diacyl-t -glyceto(3)phosphoethanolamine (3), 1,2-diacyl-t -glyceto(3)phosphoinositol (4), 1,2-diacyl-t -glyceto(3)phospho-L-serine and (5), l,2-diacyl-t -glyceto(3)phospho(3)-t -glycetol.

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined chiefly by its oil, free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

Food. Lecithin is a widely used nutritional supplement rich ia polyunsaturated fatty acids, phosphatidylcholine, phosphatidylethanolamine, phosphatidjhnositol, and organically combiaed phosphoms, with emulsifying and antioxidant properties (38). 

Phospholipids are important constituents of cell membranes and are of two kinds. Glycerophospholipids, such as phosphatidylcholine and phos-phatidylethanolamine, are closely related to fats in that they have a glycerol backbone esterified to two fatty acids (one saturated and one unsaturaled) and to one phosphate ester. Sphingomyelins have the amino alcohol sphingo-sine for their backbone. 

Diacylglycerol is glycerol esterified to two fatty acids at the sn-1 and sn-2 positions. It is a membrane-embedded product of phospholipase C action and an activator of protein kinase C. It is also an intermediate in the biosynthesis of triacylglycerol, phosphatidyletha-nolamine and phosphatidylcholine. 

The presence of impurities like free fatty acids in egg or soybean phosphatidylcholine, or in the (semi)synthetic phosphatidylcholines (e.g., DMPC, DPPC, DSPC) can be detected by monitoring the electrophoretic behavior of liposome dispersions of these phospholipids in aqueous media with low ionic strength a negative charge will be found on these liposomes when free fatty acids are present in the bilayers. 

The regulation of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine biosynthesis is driven by the availability of free fatty acids. Those that escape oxidation are preferentiaUy converted to phos-phohpids, and when this requirement is satisfied they are used for triacylglycerol synthesis. 

Phosphatidylcholine, commonly known as lecithin, is the most commonly occurring in natnre and consists of two fatty add moieties in each molecule. Phosphati-dylethanolamine, also known as cephahn, consists of an amine gronp that can be methylated to form other compounds. This is also one of the abundant phospholipids of animal, plant, and microbial origin. Phosphatidylserine, which has weakly acidic properties and is found in the brain tissues of mammals, is found in small amounts in microorganisms. Recent health claims indicate that phosphatidylserine can be used as a brain food for early Alzheimer s disease patients and for patients with cognitive dysfunctions. Lysophospholipids consist of only one fatty acid moiety attached either to sn-1 or sn-2 position in each molecule, and some of them are quite soluble in water. Lysophosphatidylchohne, lysophosphatidylserine, and lysophos-phatidylethanolamine are found in animal tissues in trace amounts, and they are mainly hydrolytic products of phospholipids. 

FIGURE 12.4 (A) Diagrammatic representation of the separation of major simple lipid classes on silica gel TLC — solvent system hexane diethylether formic acid (80 20 2) (CE = cholesteryl esters, WE = wax esters, HC = hydrocarbon, EEA = free fatty acids, TG = triacylglycerol, CHO = cholesterol, DG = diacylglycerol, PL = phospholipids and other complex lipids). (B) Diagrammatic representation of the separation of major phospholipids on silica gel TLC — solvent sytem chloroform methanol water (70 30 3) (PA = phosphatidic acid, PE = phosphatidylethanolamine, PS = phosphatidylserine, PC = phosphatidylcholine, SPM = sphingomyelin, LPC = Lysophosphatidylcholine). 

FIG. 11 Order parameter variation along acyl chains in red cell ghosts ( ), small unilamellar vesicles of egg phosphatidylcholine (V), and paraffin oil (+), as determined by the fluorescence anisotropy decay of the w-anthroyloxy fatty acid probes. (Reprinted by permission from Ref. 12.)... 

PC = phosphatidylcholine, PE = phosphatidylethanolamine, PS = phosphatidylserine, PI = phosphati-dylinositol, Sph = sphingomyelin, FA = fatty acid, PA = phosphatidic acid, LPI = lyso-PI, CL = car-diolipin, LPC = Iyso-PC, CHO = cholesterol, CE = cholesterol ester, TG = triglycerides. 

The few examples of deliberate investigation of dynamic processes as reflected by compression/expansion hysteresis have involved monolayers of fatty acids (Munden and Swarbrick, 1973 Munden et al., 1969), lecithins (Bienkowski and Skolnick, 1974 Cook and Webb, 1966), polymer films (Townsend and Buck, 1988) and monolayers of fatty acids and their sodium sulfate salts on aqueous subphases of alkanolamines (Rosano et al., 1971). A few of these studies determined the amount of hysteresis as a function of the rate of compression and expansion. However, no quantitative analysis of the results was attempted. Historically, dynamic surface tension has been used to study the dynamic response of lung phosphatidylcholine surfactant monolayers to a sinusoidal compression/expansion rate in order to mimic the mechanical contraction and expansion of the lungs. 

LOX-catalyzed oxidation of LDL has been studied in subsequent studies [26,27]. Belkner et al. [27] showed that LOX-catalyzed LDL oxidation was not restricted to the oxidation of lipids but also resulted in the cooxidative modification of apoproteins. It is known that LOX-catalyzed LDL oxidation is regio- and enantio-specific as opposed to free radical-mediated lipid peroxidation. In accord with this proposal Yamashita et al. [28] showed that LDL oxidation by 15-LOX from rabbit reticulocytes formed hydroperoxides of phosphatidylcholine and cholesteryl esters regio-, stereo-, and enantio-specifically. Sigari et al. [29] demonstrated that fibroblasts with overexpressed 15-LOX produced bioactive minimally modified LDL, which is probably responsible for LDL atherogenic effect in vivo. Ezaki et al. [30] found that the incubation of LDL with 15-LOX-overexpressed fibroblasts resulted in a sharp increase in the cholesteryl ester hydroperoxide level and a lesser increase in free fatty acid hydroperoxides. 

The rate of production of DAG in the cell does not occur linearly with time, but rather it is biphasic. The first peak is rapid and transient and coincides with the formation of IP3 and the release of Ca2+ this DAG is therefore derived from the PI-PLC catalyzed hydrolysis of phosphatidylinositols [1]. There is then an extended period of enhanced DAG production that is now known to be derived from the more abundant phospholipid phosphatidylcholine (PC), which has a different composition of fatty acid side chains [9]. Although DAG may be generated directly from PC through the action of PC-PLC, it can also be formed indirectly from PC. In this pathway, PC is first hydrolyzed by PLD to give choline and phosphatidic acid, which is then converted to DAG by the action of a phos-phatidic acid phosphatase [10,11 ]. 

Kaya K, Nohara K. 1987. Effect of di-n-octyl phthalate on fatty acid composition of phosphatidylcholine in tetrahymena. Chem Biol Interactions 64 93-101. 

---