Phosphatidylcholine acylation

Redgrave, T. G., Rakic, V., Mortimer, B.-C., and Mamo, J. C. L. (1992), Effects of sphingomyelin and phosphatidylcholine acyl chains on the clearance of triacylglycerol-rich lipoproteins from plasma. Studies with lipid emulsions in rats, Biochim. Biophys. Acta, 1126, 65-72. 

Smaby JM, Momsen MM, Brockman HL, Brown RE. Phosphatidylcholine acyl unsaturation modulates the decrease in interfacial elasticity induced by cholesterol. Biophys J 1997 73 1492-1505. 

Smaby JM, Momsen MM, Brockman HL, Brown RE. Phosphatidylcholine acyl chain unsaturation modulates the decrease in interfacial elasticity induced by cholesterol. Biophys J 1997 73 1492-1505. Souvignet C, Pelosin JM, Daniel S, Chambaz EM, Ransac S, Verger R. Activation of protein kinase C in lipid... 

Phase transitions have been characterized in a number of different pure and mixed lipid systems. Table 9.1 shows a comparison of the transition temperatures observed for several different phosphatidylcholines with different fatty acyl chain compositions. General characteristics of bilayer phase transitions include the following ... 

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.)... 

Therefore, it is currently believed that anandamide is formed from membrane phospholipids (Fig. 4) through a pathway that involves (1) a trans-acylation of the amino group of phosphatidylethanolamine with arachidonate from the sn-1 position of phosphatidylcholine and (2) a D-type phosphodiesterase activity on the resulting A-arachidonylphosphati-dylethanolamide (NAPE). Synthesis of anandamide is presumably regulated at the levels of both enzymes, the A-acyltranferase and the phospholipase D, by stimuli that raise intracellular calcium or by receptors linked with cAMP and PKA. It has been shown that anandamide is formed when neurons are depolarized and, therefore, the intracellular calcium ion levels are elevated (Cadas, 1996). 

Cholesterol esters are produced by transferring an acyl moiety from acyl-CoA or from phosphatidylcholine onto the cholesterol hydroxyl group. The latter process is catalyzed by phosphatidylcholine cholesterol acyltransferase ... 

The length of the acyl side chains of a phosphatidylcholine derivative have significant effects upon the rate with which PLC i( catalyzes the hydrolysis of... 

Table 3. The effect of acyl chain length on PLCBc activity toward soluble phosphatidylcholine derivatives. The differences in the experimental data are likely due to the use of different assay conditions... 

The role of protein kinase C in many neutrophil functions is undisputed and has been recognised for some time. For many years it was believed that the source of DAG, the activator of protein kinase C, was derived from the activity of PLC on membrane phosphatidylinositol lipids. Whilst this enzyme undoubtedly does generate some DAG (which may then activate protein kinase C), there are many reasons to indicate that this enzyme activity is insufficient to account for all the DAG generated by activated neutrophils. More recently, experimental evidence has been provided to show that a third phospholipase (PLD) is involved in neutrophil activation, and that this enzyme is probably responsible for the majority of DAG that is formed during cell stimulation. The most important substrate for PLD is phosphatidylcholine, the major phospholipid found in neutrophil plasma membranes, which accounts for over 40% of the phospholipid pool. The sn-1 position of phosphatidylcholine is either acyl linked or alkyl linked, whereas the sn-2 position is invariably acyl linked. In neutrophils, alkyl-phosphatidylcholine (1-0-alky 1-PC) represents about 40% of the phosphatidylcholine pool (and is also the substrate utilised for PAF formation), whereas the remainder is diacyl-phosphatidylcholine. Both of these types of phosphatidylcholine are substrates for PLD and PLA2. 

For comparison, 2-parinaroyl-phosphatidylcholine (PPC) was also incorporated into the membrane preparations. For the Torpedo membranes, the acyl chain order measured by PPI was found to be lower than that by PPC, whereas the opposite was true for the vesicles. This inversion strongly suggests that PI has different interactions with certain membrane components compared to PC. In contrast, the correlation times of PPI and PPC were only slightly different in Torpedo membranes, and the values showed little difference with those measured in vesicles. 

M. Straume and B. J. Litman, Equilibrium and dynamic structure of large, unilamellar, unsaturated acyl chain phosphatidylcholine vesicles. Higher order analysis of 1,6-diphenyl-... 

M. Caffrey and G. W. Feigenson, Fluorescence quenching in model membranes. 3. Relationship between calcium adenosinetriphosphatase enzyme activity and the affinity of the protein for phosphatidylcholines with different acyl chain characteristics, Biochemistry 20, 1949-1961 (1981). 

It is interesting that modifying solution conditions by adding different concentrations of ethanol can produce a biphasic effect on melting transition temperatures of lipid-like systems (e.g., acyl chains of hydrocarbons). For example, low concentrations of ethanol reduce the Tm of phosphatidylcholine bilayers, whereas higher concentrations increase the Tm of the same system.122 This effect has been shown to depend upon acyl chain length and can be explained by the... 

Fig. 1.9 Structures of charge neutral (phosphatidylcholine) and acidic (phosphatidylserine) phospholipids together with the moderately lipophilic and basic drug chlorphentermine. The groupings R1 and R2 refer to the acyl chains of the lipid portions.

The other phospholipids can be derived from phosphatidates (residue = phosphatidyl). Their phosphate residues are esterified with the hydroxyl group of an amino alcohol choline, ethanolamine, or serine) or with the cyclohexane derivative myo-inositol. Phosphatidylcholine is shown here as an example of this type of compound. When two phosphatidyl residues are linked with one glycerol, the result is cardiolipin (not shown), a phospholipid that is characteristic of the inner mitochondrial membrane. Lysophospholipids arise from phospholipids by enzymatic cleavage of an acyl residue. The hemolytic effect of bee and snake venoms is due in part to this reaction. 

This enzyme [EC 2.3.1.43] catalyzes the reaction of a phosphatidylcholine with a sterol to produce a sterol ester and a 1-acylglycerophosphocholine. The acyl moiety transferred can be a palmitoyl, oleoyl, or linoleoyl group. A number of sterols, including cholesterol, can act as the acyl acceptor. 

PHOSPHOLIPASE A2 Phosphatidylcholine 2-acyl hydrolase, PHOSPHOLIPASE A2 Phosphatidylcholine, hydrolysis of, PHOSPHOLIPASE A2 PHOSPHOLIPASE D... 

FIGURE 21-31 Biosynthesis of sphingolipids. Condensation of palmitoyl-CoA and serine followed by reduction with NADPH yields sphinganine, which is then acylated to N-acylsphinganine (a ceramide). In animals, a double bond (shaded pink) is created by a mixed-function oxidase, before the final addition of a head group phosphatidylcholine, to form sphingomyelin glucose, to form a cerebroside. 

The fourth major lipoprotein type, high-density lipoprotein (HDL), originates in the liver and small intestine as small, protein-rich particles that contain relatively little cholesterol and no cholesteryl esters (Fig. 21-40). HDLs contain apoA-I, apoC-I, apoC-II, and other apolipoproteins (Table 21-3), as well as the enzyme lecithin-cholesterol acyl transferase (LCAT), which catalyzes the formation of cholesteryl esters from lecithin (phosphatidylcholine) and cholesterol (Fig. 21-41). LCAT on the surface of nascent (newly forming) HDL particles converts the cholesterol and phosphatidylcholine of chylomicron and VLDL remnants to cholesteryl esters, which begin to form a core, transforming the disk-shaped nascent HDL to a mature, spherical HDL particle. This cholesterol-rich lipoprotein then returns to the liver, where the cholesterol is unloaded some of this cholesterol is converted to bile salts. 

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