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1,674 records · Page 93Linked to original sources
PubMed1983

The interaction of dialkyl ether lecithins with phospholipase A2 (Naja naja naja).

Dialkyl lecithins are nonhydrolyzable substrate analogues for phospholipase A2 (Naja naja naja). Short chain dialkyl lecithins (which form monomers and micelles), and long chain ether-linked lecithins (which form bilayers or can be solubilized in detergent micelles) have been used to study phospholipase A2/phospholipid interactions. The results of gel filtration, 1H and 31P NMR spectroscopy, kinetic assays and UV difference spectroscopy show that binding of the ether-linked lecithins is independent of metal ion in pure lecithin systems (monomer, micelle, or bilayer), but requires Ca2+ for tight binding when Triton X-100 is used to solubilize the lecithin in mixed micelles. The apparent KD for dihexadecyl phosphatidylcholine is 2 mM in sonicated vesicles, but is increased to 6 mM in Triton-mixed micelles in the presence of Ca2+. When phospholipase A2 binds monomeric and micellar dialkyl lecithin, the lecithin phosphate resonance is broadened considerably, indicating that head group motion is restricted. Ca2+ enhances this interaction with the head group in these pure lipid systems. In similar 31P NMR experiments with dihexadecyl phosphatidylcholine solubilized in Triton X-100 mixed micelles, phospholipase A2 does not cause comparable broadening of the phosphate resonance, even in the presence of Ca2+ where gel filtration shows binding occurs. The kinetic effect of the ether-linked lipid inhibitors on phospholipase activity toward ester-linked lecithins is also modulated by the presence of Triton X-100. Ether-linked lecithins are much more potent inhibitors in two-component (dialkyl- diacyl-) lecithin micelles and bilayers than in complex mixed micelles with Triton X-100. Detergent-induced changes in the characteristics of the micellar interface are implicated in this inhibition phenomenon. The interaction of phospholipase A2 with sonicated vesicles of dihexadecyl phosphatidylcholine has also been examined by 1H and 31P NMR spectroscopy. When phospholipase A2 binds to vesicles, it promotes loss of encapsulated lanthanide ions, and appears to accelerate transbilayer phospholipid "flip-flop" rates. These results are discussed in terms of membrane asymmetry studies using phospholipase A2.

Calcium↗
PubMed1982

Changes in the composition of fatty chains of diacyl, alkylacyl and alkenylacyl ethanolamine and choline phosphoglycerides during the development of chick heart ventricular cells. High accumulation of 22-carbon fatty acid in ether phospholipids.

The phospholipids of embryonic chick ventricular cells were analysed at various developmental stages with respect to the composition of alkylacyl, alkenylacyl and diacyl ethanolamine and choline phosphoglycerides and for the fatty chain composition of these lipid classes. The percentage of alkylacyl and alkenylacyl choline phosphoglycerides increased in the course of the development. The fatty chain composition of ether-linked phosphoglycerides was significantly different from that of the diacyl compound. In general, both ether choline and ethanolamine phosphoglycerides consisted of a significantly higher percentage of 22-carbon fatty chains, such as 22:4, 22:5 and 22:6, compared to that of the diacyl compounds, throughout the earlier stage of development. During development, there was a dramatic increase of 20:4 and a decrease of 22:6, mainly in total ethanolamine phosphoglycerides but also in choline phosphoglycerides. A particularly significant decrease of 22:6 was found with diacyl ethanolamine phosphoglycerides. When 14C-labeled 22:4 and 3H-labeled 20:4 were incorporated into the ethanolamine and choline phosphoglycerides of ventricles in vitro, it was observed that 22:4 was mainly associated with ether phospholipids, especially the ethanolamine alkyl ether phospholipids, suggesting that there is a high selectivity of 22-carbon fatty acid to ether phospholipids during the synthesis of these compounds.

Aging↗
PubMed1980

A comparative study of the lipid composition of white, intermediate, red and heart muscle in rats.

The detailed lipid composition of white (rectus femoris), intermediate (soleus), red (diaphragm) and heart muscle isolated from fed and 48-h-fasted male rats was determined. 1. Contents of phospholipid and total cholesterol were high, with increasing levels of aerobic oxidation in muscles. Triacylglycerol content was highest in red muscle, moderate in heart and intermediate muscle and lowest in white muscle. 2. The molar percentages of phosphatidylethanolamine and cardiolipin were high and those of phosphatidylcholine, phosphatidylinositol and phosphatidylserine were low, with increasing levels of aerobic oxidation in muscles. 3. The molar percentage of alkenyl-acyl type was higher in phosphatidylethanolamine than in phosphatidylcholine which consisted predominantly of diacyl type. Heart and intermediate muscle had lower content of alkenyl-acyl type and higher contents of diacyl type in phosphatidylethanolamine as compared with white muscle, whereas the class composition in phosphatidylcholine were nearly the same among the muscles examined. 4. The contents of 18 : 0 in phosphatidylcholine and 18 : 0, 18 : 2 and 20 : 4 in phosphatidylethanolamine were high and those of 16 : 0 in phosphatidylcholine and 22 : 6 in phosphatidylethanolamine were low, accompanying approximately the increase in the levels of aerobic oxidation in muscles. The fatty acid composition of triacylglycerol was similar in all the muscles examined. 5. The fasting had little effect on the lipid patterns of the various types of muscles except for those of phospholipids in heart muscle. These results were discussed in relation to the cell structure and function for energy metabolism in various muscles.

Animals↗
PubMed1994

Plasmenylethanolamine in human intestinal mucosa detected by an improved method for analysis of phospholipid.

Analysis of phospholipid and their fatty acid composition of human intestinal mucosa was performed by an method elaborated to analyze the limited amount of sample with 2-dimensional TLC followed by lipid-phosphorus determination. Using this method, plasmenylethanolamine was detected in human intestinal mucosa and accounted for about 7% of phospholipid in small and large intestinal mucosa. The amounts of polyunsaturated fatty acids of phosphatidylethanolamine were higher than those of other phosphoglycerides in intestinal mucosa, hence, inflammation-related eicosanoids may originate from ethanolamine containing phospholipid.

Arachidonic Acid↗
PubMed1993

Long-term fatty acid modification of endothelial cells: implications for arachidonic acid distribution in phospholipid classes.

Human umbilical vein endothelial cells were cultured in various fatty acid-modified media until equilibrium conditions were reached (7-8 days). The effects on the fatty acid composition of phospholipid classes and on the metabolism of arachidonic acid (20:4(n-6)) were studied. The results showed that in every phospholipid class large changes in fatty acid composition, including 20:4(n-6) content, were induced by long-term modification with unsaturated as well as saturated fatty acids. However, the mean levels of saturated and unsaturated fatty acids per phospholipid class remained relatively constant, except for cells modified with oleic acid, which showed an increase in monounsaturated fatty acids at the expense of both saturated and polyunsaturated fatty acids. The rate of incorporation of radiolabeled 20:4(n-6) in endothelial lipids was not influenced by long-term fatty acid modification. Cells modified with 20:4(n-6) (having a high 20:4(n-6) content) tended to "store" excess 20:4(n-6) as the elongated product 22:4(n-6) mainly in phosphatidylserine and ethanolamine phospholipids. On the other hand, endothelial cells modified with 20:5(n-3) (having a low 20:4(n-6) content) differed typically from other fatty acid-modified cells by a relatively high level and high incorporation rate of 20:4(n-6) in phosphatidylinositol, with a low extent of elongation. These results indicate extensive homeostatic control of membrane unsaturation in each phospholipid class and economical control of 20:4(n-6) content in all modified endothelial cells, irrespective of a considerable variation of 20:4(n-6) levels in cellular lipids. Moreover, the observed maintenance of a critical level of 20:4(n-6) in phosphatidylinositol, when 20:4(n-6) supply was strongly decreased, may be important for maintaining proper signal transduction upon endothelial cell stimulation.

Arachidonic Acid↗
PubMedDate not supplied

[Lysophospholipids and their diacyl derivatives in rat testicular mitochondria during hypoxia].

Content of lysophospholipids and their diacyl derivatives was astimated in intact and destructed mitochondria of rat spermatic glands in acute hypoxic hypoxia by means of thin-layer chromatography on silica gel. A ratio of phospholipid lysoforms was found to increase with simultaneous decrease in cardiolipin and rhosphatidyl ethanolamine fractions. The minimal alteration in phospholipid spectrum occurred in mitochondrial membranes.

Animals↗
PubMed1997

Biosynthesis of plasmenylethanolamine (1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine) in the guinea pig heart.

In this study, the isolated guinea pig heart was pulse-labeled with a precursor of ethanolamine glycerophospholipid, and then chased with the non-radioactive compound for 0-8 h. Labeling with hexadecanol revealed that plasmanylethanolamine was the immediate precursor of plasmenylethanolamine, but a substantial portion of the label was also found in phosphatidylethanolamine. When ethanolamine was used as the precursor, the labeling of plasmenylethanolamine was between 50-65% of the labeling of phosphatidylethanolamine, and this ratio was maintained throughout the perfusion. The ratio of labeling is similar to the ratio of pool sizes of these ethanolamine glycerophospholipid in the heart, which implies that the CDP-ethanolamine pathway is also important for plasmenylethanolamine biosynthesis. The role of diradylglycerol in the synthesis of each ethanolamine glycerophospholipid was also investigated. The ratio of 1-alkenyl-2-acyl glycerol to total diradylglycerol content was 7% in the homogenate and 32% in the microsomes. However, ethanolamine phosphotransferase displayed a distinct selectivity towards 1-alkenyl-2-acyl glycerol. Kinetic studies revealed that the synthesis of phosphatidylethanolamine was inhibited by 1-alkenyl-2-acyl glycerol, but the formation of plasmenylethanolamine was not affected by 1,2-diacylglycerol. In addition, the inhibition of ethanolamine phosphotransferase by 1-alkyl-2-acyl glycerol appears to be an important mechanism for the coordination of plasmenylethanolamine biosynthesis via the desaturase reaction and the CDP-ethanolamine pathway.

Animals↗
PubMed1998

Characterizations of Pneumocystis carinii and rat lung lipids: glyceryl ethers and fatty alcohols.

Pneumocystis carinii carinii and rat lung phospholipids contained 3-6% 1-alkyl-2-acyl glycerols composed of the glyceryl ether species, 1-O-octadecyl glycerol (batyl alcohol), 1-O-octadec-9-enyl glycerol (selachyl alcohol), 1-O-hexadecyl glycerol (chimyl alcohol), and 1-O-hexadec-9-enyl glycerol. Of the major phospholipid classes, phosphatidylinositol (PI) and phosphatidylserine contained the highest percentage of alkyl acyl glycerols. Methylprednisolone treatment caused an increase in alkyl acyl PI of rat lung lipids from 12% to 45%. As the PI concentration in lung phospholipids increases in rats treated with methylprednisolone, the increase in alkyl acyl PI was substantial; the proportions of alkyl acyl phosphatidylethanolamine and alkyl acyl lyso phosphatidylcholine (PC) also increased. Pneumocystis phospholipids contained higher proportions of alkyl acyl PC than the phospholipids of the lungs from normal and immunosuppressed uninfected rats. The glyceryl ether compositions of P. carinii carinii PC and lyso PC were similar, which suggests that lyso PC in the organism is derived by phospholipase A2 action on PC. This was not the case for PC and lyso PC of the lung controls. Analysis of the free fatty alcohols, precursors of glyceryl ethers identified only saturated species in P. carinii carinii and rat lung controls. Thus, the introduction of a double bond in the alcohol moiety of glyceryl ethers occurs after formation of the ether linkage between fatty alcohol and the glyceryl backbone.

Animals↗