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At least 19 recordsLinked to original sources
PubMed1976

A method for the modulation of membrane fluidity: homogeneous catalytic hydrogenation of phospholipids and phospholipids and phospholipid-water model biomembranes.

The fatty acids associated with phospholipids of cell membranes, and particularly their degree of unsaturation, contribute to the fluidity of their structure and hance determine many of their biological properties. We describe a technique for modulating membrane fluidity which consists of hydrogenating the unsaturated double bonds of membrane phospholipids. This has been accomplished using a homogeneous catalyst. The process has been applied to phospholipids in organic solvents, to phospholipids dispersed as multibilayers in aqueous systems, and also to sonicated preparations of phospholipids arranged as single bilayer vesicles. Preliminary experiments have also been performed with biological membranes. These results indicate that the process of homogeneous catalysis for the modulation of lipid fluidity of biological cell membranes may have considerable future biological and biochemical application.

Catalysis↗
PubMed1976

Role of phospholipids in the calcium-dependent ATPase of the sarcoplasmic reticulum. Enzymatic and ESR studies with phospholipid-replaced membranes.

Three types of partially purified ATPase enzymes having different phospholipid contents and compositions have been prepared: (a) an enzyme whose phospholipid moiety has been replaced predominantly by dioleoyl lecithin (DOL-enzyme), with about the same phospholipid content as the original sarcoplasmic reticulum, (b) dipalmitoyl lecithin-replaced enzyme whose phospholipid content is 30% of that of DOL-enzyme (DPL-enzyme), and (c) a partially delipidated enzyme with about the same phospholipid content as DPL-enzyme but with the original sarcoplasmic reticulum phospholipid composition (del-enzyme). The temperature dependence of Ca2+-activated ATPase activity of these preparations showed clearcut differences; with DOL-enzyme there was no appreciable break in the Arrhenius plot in the 3-40 degrees range; DPL-enzyme showed a break at 29 degrees, and del-enzyme and sarcoplasmic reticulum one at 18 degrees. Transition temperatures obtained from ESR studies with the use of spin-labeled stearic acid incorporated into the membranes agreed with those derived from ATPase assays. Thermo-dynamic analysis of the ATP hydrolysis rates shows that DPL-enzyme has considerably larger values of activation enthalpy and activation entropy below the transition temperature (29 degrees) than those of the other preparations, while all enzyme preparations show similar free energies of activation. The ESR data show that below their transition temperatures DPL-enzyme, and to a lesser degree del-enzyme, have a strongly restricted motion of their phospholipid molecules as compared with either DOL-enzyme or sarcoplasmic reticulum. Studies on the formation and decomposition of phosphoenzyme have been carried out with the three types of ATPase preparations. At 0 degrees, the rate of inorganic phosphate liberation is 8 times lower in DPL-enzyme than in del-enzyme with little difference in the steady state level of phosphoenzyme. In DOL-enzyme, the level of phosphoenzyme and the rate of inorganic phosphate liberation are 1.8 and 3.5 times higher than the corresponding values obtained with del-enzyme. Addition of ADP to the phosphorylated intermediate of DPL-enzyme induces a fast reversal of the phosphorylation reaction. These results indicate that the physical state of the phospholipid molecules associated with the enzyme affects the decomposition of phosphoenzyme, with little effect on the phosphorylation reaction and its reversal.

Adenosine Triphosphatases↗
PubMed1992

Caldesmon-phospholipid interaction. Effect of protein kinase C phosphorylation and sequence similarity with other phospholipid-binding proteins.

Recently published data [Vorotnikov & Gusev (1990) FEBS Lett. 277, 134-136] indicate that smooth muscle caldesmon interacts with a mixture of soybean phospholipids (azolectin). Continuing this investigation, we found that duck gizzard caldesmon interacts more tightly with acidic (phosphatidylserine) than with neutral (phosphatidylcholine) phospholipids. A high concentration of Ca2+ (50 microM) decreased the interaction of caldesmon with phosphatidylserine. Among chymotryptic peptides of caldesmon, only those having molecular masses of 45, 40, 23, 22 and 20 kDa were able to specifically interact with phospholipids. These peptides, derived from the C-terminal part of caldesmon, contained the sites phosphorylated by Ca2+/phospholipid-dependent protein kinase, and phosphorylation catalysed by this enzyme decreased the affinity of these peptides for phospholipids. In the presence of Ca2+, calmodulin competed with phospholipids for the interaction with the caldesmon peptides. The C-terminal part of caldesmon contains three peptides with a primary structure similar to that of the calmodulin- and phospholipid-binding site of neuromodulin. These sites may be involved in the interaction of caldesmon with calmodulin and phospholipids.

Amino Acid Sequence↗
PubMed1992

The effect of dietary safflower phospholipid and soybean phospholipid on plasma and liver lipids in rats fed a hypercholesterolemic diet.

The effect of dietary safflower phospholipid (Saf-PL) and soybean phospholipid (Soy-PL) on plasma, liver, and fecal lipids in rats fed a hypercholesterolemic diet was compared with that of triglyceride mixture (controls). Triglyceride mixture (SP-Oil) of safflower oil and palm oil (8:2) contained almost comparable amounts of linoleic acid to safflower phospholipid or soybean phospholipid. Concentration of total cholesterol in plasma of rats fed the Saf-PL and Soy-PL diets were significantly decreased in comparison with that of the SP-Oil diet. Similarly, both Saf-PL and Soy-PL induced a reduction in the concentration of liver cholesterol compared with SP-Oil; Saf-PL indicated the lowest value. Saf-PL only significantly increased the level of high density lipoprotein (HDL) cholesterol. The level of chylomicron plus very low density lipoprotein (VLDL) cholesterol was lower in rats fed the Saf-PL and Soy-PL diets than that of the SP-Oil diet. The activity of plasma lecithin-cholesterol acyltransferase (LCAT) was increased in rats fed Saf-PL and Soy-PL. Saf-PL and Soy-PL caused an enhanced excretion of fecal neutral steroids, but not acidic steroids compared with SP-Oil. These results suggest that, in addition to soybean phospholipid, safflower phospholipid suppresses the elevation of plasma and liver cholesterol and that this effect may be brought about by inhibiting the absorption of cholesterol in the small intestine.

Animals↗
PubMed1977

The interaction of lanthanide and calcium salts with phospholipid bilayer vesicles: the validity of the nuclear magnetic resonance method for determination of vesicle bilayer phospholipid surface ratios.

Contrary to a recent report (B. Sears et al., Biochemistry 15 (1976) 1635), it has been determined that the ratio of the number of phospholipids on the inner and outer surfaces of phospholipid bilayer vesicles can be accurately determined by NMR paramagnetic ion shift reagent studies of vesicles. It is concluded that the metal interacts with all of the phospholipid on the exposed bilayer surface. A ratio of outer phospholipid to inner surface phospholipid of 2.1 +/- 0.1 is obtained regardless of the nucleus studied, position of the nucleus relative to the metal ion binding site, molar ratio of metal to phospholipid over three orders of magnitude, or location of the metal ion of the inside or outside of the vesicle. Additionally, P-31 NMR studies using LaC13 and CaC12 indicate that Ca2+ weakly interacts with egg PC vesicles and that the lanthanides are adequate substitutes for Ca2+ since neither metal is found to perturb measurably the average polar head group conformation.

Calcium↗
PubMed1992

Enrichment of saturated fatty acid containing phospholipids in sheep brain serotonin receptor preparations: use of microwave irradiation for rapid transesterification of phospholipids.

During enrichment of the 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)-binding serotonin 5-HT1A receptors from sheep brain gray matter (membrane isolation, detergent solubilization and reconstitution into vesicles) a consistent and striking increase in the composition of saturated fatty acids was observed in phospholipids which were coisolated with the receptors. A rapid procedure has been developed for the methylation of free and phospholipid linked fatty acids which were thus analyzed by gas chromatography-mass spectrometry (GC/MS). Esterification of free fatty acids and transesterification of phospholipid linked fatty acids were achieved with 14% boron trifluoride in methanol (BF3-CH3OH) in 20 s and 50 s, respectively, under low power microwave irradiation (60 W) with a post-reaction cooling of less than 5 min. This is in contrast to the conventional method of heating in a boiling water bath for 10-15 min with BF3-CH3OH which is inevitably preceded by time-consuming and inconvenient clamping of vials and followed by cooling for 10 min before the vials can be safely opened. Analysis of fatty acid profiles in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) from egg yolk, phosphatidylinositol (PI) from bovine liver and phosphatidylserine (PS) from bovine brain by both techniques showed comparable results. During detergent solubilization of sheep brain gray matter, the overall proportion of saturated fatty acids in PE (major lipid), PI, PC (major lipid) and PS increased from 50-60% in sheep brain phospholipids to 70-75% in 1.5% CHAPS solubilized, reconstituted and biologically active serotonin 5-HT1A preparations. In sharp contrast, the proportions of saturated fatty acids in 1.5% Triton X-100 solubilized PE (48.1%) (major lipid), PI (63.6%), PC (60.6%) (major lipid) and PS (62.2%) were not significantly different from those in the original sheep brain membranes. Strikingly, this was coupled with the occurrence of very low levels of 5-HT1A receptor activity in the Triton X-100 solubilized preparations. The abundance of 5-HT1A sites in the enriched vesicles obtained only from the CHAPS-solubilized preparations was further confirmed by specific radiolabeling of a 58-kDa polypeptide by the 5-HT1A specific ligand p-aminophenylethyl-m-trifluoromethylphenylpiparazine (PAPP) which was coupled to a 125I-labeled, photoreactive, heterobifunctional cross-linker, sulfosuccinimidyl-2-(p-azidosalicylamido)ethyl-1,3'-dithiopropiona te (SASD). Thus CHAPS-solubilized 5-HT1A receptor preparations are depleted in the more rigid lipids such as sphingolipids and cholesterol, (Banerjee et al. (1990) Biochim. Biophys. Acta 1044, 305-314), but are enriched in vesicle-stabilizing, phospholipid-linked saturated fatty acids which in turn probably stabilize the heptahelical, membrane bound 5-HT1A receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1979

Rotational relaxation times of 1,6-diphenyl-1,3,5-hexatriene in phospholipids isolated from LM cell membranes. Effects of phospholipid polar head-group and fatty acid composition.

Phospholipids were isolated from mitochondrial, microsomal, and plasma membranes of LM cells and fractionated into individual phospholipid classes on silicic acid columns. The fatty acid composition and the rotational relaxation time of 1,6-diphenyl-1,3,5-hexatriene (DPH) were determined for each phospholipid class. Sphingomyelin was the only phospholipid isolated from LM cell membranes that showed a phase transition within the temperature range investigated, 5-40 degrees C. The rotational relaxation times for DPH were lowest in phosphatidylcholine in all the membrane fractions. Phosphatidylcholine isolated from the three membrane fractions of choline-supplemented cells had similar rotational relaxation times and phosphatidylcholine isolated from microsomal membranes of linoleate-supplemented cells had lower rotational relaxation times. The results indicate that the differences in the rotational relaxation times of DPH between mitochondrial, microsomal, and plasma membrane phospholipids could be explained primarily by differences in the polar head-group composition, while differences in the fatty acid composition had only a minor effect. This provides a basis for understanding how the different lipid components in these cells contribute to membrane fluidity.

Animals↗
PubMed1975

Mutants of Escherichia coli defective in membrane phospholipid synthesis. Effect of cessation of net phospholipid synthesis on cytoplasmic and outer membranes.

The effect of cessation of net phospholipid synthesis on the cytoplasmic and outer membranes of Escherichia coli was investigated in a mutant strain defective in the first enzyme of phospholipid synthesis, the sn-glycerol-3-phosphate (glycerol-P) acyltransferase. The glycerol-P (glycerol) auxotropic phenotype of this strain resulted from an altered membranous glycerol-P acyltransferase activity with an apparent Km for glycerol-P 10 times higher than that of the parental activity. When net phospholipid synthesis was halted during glycerol deprivation, both soluble and cell envelope protein synthesis continued. Fractionation of the membranes derived from glycerol-supplemented and glycerol-deprived cultures by isopycnic banding in sucrose gradients revealed that both the cytoplasmic and outer membranes of the deprived culture banded at higher buoyant densities. The protein/phospholipid ratio of both the cytoplasmic and outer membranes increased approximately 60% during the period of glycerol deprivation. The distribution of two cytoplasmic membrane activities, NADH oxidase and 1-acylglycerol-P acyltransferase, and an outer membrane activity, phospholipase A1, showed that the total membranes derived from glycerol-deprived cultures were separated cleanly into cytoplasmic and outer membrane fractions. Both cytoplasmic and outer membrane proteins were synthesized and integrated into their respective membranous structures when net phospholipid synthesis was halted. Hence, the biosynthesis of membrane phospholipid and membrane protein are not tightly coupled. Further, these data suggest that cellular control mechanisms exist which maintain the protein content of both membranous structures below the point where they are saturated with protein.

Bacterial Proteins↗
PubMed1975

Studies on the synthesis of liver phospholipids and the turnover of plasma phospholipids in non pregnant female rats using radioactive palmitate.

Using the tracer method and a compartmental model we found that 0.9 mumoles plasma free fatty acids per min are esterified to liver phospholipids. The turnover rate of plasma phospholipid fatty acids was determined to be 0.5 mumoles phospholipid fatty acids per min. The turnover time of the plasma phospholipid fatty acids was calculated to be 0.9 hours. The results indicate that only 69 per cent of plasma free fatty acids esterified to liver phospholipids are secreted by the liver into the plasma.

Animals↗
PubMed1977

[Phospholipid composition and fatty acid patterns of isolated phospholipids from rabbit reticulocyte mitochondria].

The phospholipid composition and fatty acid patterns of individual phospholipid classes were determined in mitochondria from rabbit reticulocytes. Compared to mitochondria from rat liver reticulocyte, mitochondria exhibit about twice the amount of phospholipids. The phospholipid pattern of reticulocyte mitochondria (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and cardiolipin) is comparable with other mitochondrial species. Mitochondrial fractions from reticulocytes are characterized, however, by an additional content of sphingomyelin. This sphingomyelin differs in its fatty acid composition from the sphingomyelin of the plasma membrane. The fatty acid patterns of all other phospholipids essentially correspond to those of mitochondria from other sources and to those of plasma membranes as well.

Animals↗
PubMed1976

Composition of phospholipids and phospholipid fatty acids in rat mast cells.

The composition of phospholipids and phospholipid fatty acids in isolated rat serous fluid mast cells was analyzed by thin layer chromatography, gas-liquid chromatography and mass spectrometry. The phospholipids constituted about 50% of the mast cell lipids and phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidylcholine were identified. The phosphatidylethanolamine fraction contained aldehydes and the highest proportion of unsaturated fatty acids. Sphingomyelin contained predominantly saturated fatty acids whereas the ratio unsaturated fatty acids: saturated fatty acids for the other phospholipids was more close to 1.

Animals↗
PubMed1977

Partition of inorganic ions and phospholipids in isolated cell, membrane and matrix vesicle fractions: evidence for Ca-Pi-acidic phospholipid complexes.

Electrolytes and phospholipids of cartilage fractions were partitioned by extraction with organic and aqueous solvents into six solubility groups: Electrolytes I, II and III, and Lipids I, II and III. Of the total Ca, only 4% was water soluble (Electrolytes I); 4-12% was complexed with lipids (Electrolytes II); while the majority (84-92%) was insoluble (Electrolytes III). In contrast, nearly half of the Mg and Pi were water soluble. Of the neutral phospholipid, 95% was not complexed with mineral ions (Lipids I), but 30-45% of the acidic phospholipid was (Lipids II). Ca/Pi ratios were extremely low in the water-soluble phase, but were in the range of amorphous calcium phosphate (ACP) in the insoluble. Molar ratios of the lipid-mineral complex were: Ca:Mg:Pi:acidic phospholipid, 4:3:2:2. Mg/Ca ratios in the soluble fraction were high (5.5-8.9), sufficient to stabilize ACP. Kinetic studies revealed rapid turnover of soluble Ca, insoluble turning over much more slowly. Labeling of lipid-complexed Ca was rapid in cells, but occurred later in matrix vesicles, suggesting transfer. While lipid-Ca-Pi complexes can nucleate apatite in vitro, those present in vivo inside matrix vesicles apparently do not because of the excess Mg. We conclude therefore, that in vesicle-mediated calcification, lysis of the membrane may be essential to allow release of internal Mg.

Animals↗
PubMed1977

The phospholipid-dependence of uridine diphosphate glucuronyltransferase. Phospholipid depletion and re-activation of guinea-pig liver microsomal enzyme.

More than 80% of the phospholipid component of guinea-pig liver microsomal membranes (prepared with 154mM-KCl) was removed by treatment with phospholipase A followed by extraction of the lysophosphatides and fatty acids produced with albumin. Delipidation strongly inactivated the highly active UDP-glucuronyltransferase of these preparations and activity was restored by mixtures of phosphatidylcholine and lysophosphatidylchlone. However, small quantities of lysophosphatides were still associated with the delipidated fractions after extraction with albumin and might have influenced the inactivation and re-activation observed. To eliminate these uncertainties, microsomal proteins and phospholipids were separated by gel filtration on Sephadex G-150 in the presence of cholate. This technique also strongly inactivated the enzyme but did not generate membrane-active phospholipid degradation products. High transferase activity was again restored to the delipidated protein by choline glycerophosphatides. These results confirm the view that the fully active form of microsomal UDP-glucuronyltransferase is phospholipid-dependent.

Animals↗
PubMed1975

Determinants of the formation and activity of factor V-phospholipid complexes. I. Influence of phospholipid structure.

Previous studies showed that factor V consists of multiple oligomeric forms including a minor component (form L) which contained lipid and was eluted in the excluded volume of a Sepharose 4B column. In the present and following study the hypothesis that factor V is a lipid requiring protein rather than a lipoprotein has been tested. Modification of a previous purification procedure resulted in the separation of factor V from lipoprotein. The lipid extracted from this lipoprotein was qualitatively similar to that previously isolated from form L. Removal of this lipoprotein by sucrose density gradient ultracentrifugation resulted in the isolation of factor V of high specific activity which contained no detectable phospholipid and less than 0.2% cholesterol. No component was excluded from Sepharose 4B after gel filtration of this purified preparation. It is concluded that factor V is not a lipoprotein, but rather a protein which requires lipid for its coagulant properties. To define this requirement further the ability of factor V-phospholipid complexes to accelerate the conversion of prothrombin to thrombin by factor Xa in the presence of calcium was tested. The rate of thrombin formation was highly dependent on the phospholipid employed with each active phospholipid exhibiting a characteristic optimal concentration. At 250 muM, the order of activity was phosphatidyl ethanolamine greater than phosphatidyl inositol greater than cardiolipin greater than phosphatidyl choline. Phosphatidyl serine was inert at all concentrations employed. No single fatty acid was consistently present in active lipid preparations, nor was a specific fatty acid absent from those which had no clotting activity. In comparing different lipid classes, a direct relationship between the overall degree of unsaturation and activity was not observed. However, bovine phosphatidyl inositol, which is highly unsaturated, is active, while plant phosphatidyl inositol, which contains only trace amounts of unsaturated fatty acids, were inert. At lipid concentrations below 300 muM, saturated phosphatidyl ethanolamine produced by hydrogenation of bovine phosphatidyl ethanolamine was less active than an equal concentration of the native lipid. In mixtures containing both lipids, artificially saturated phosphatidyl ethanolamine potentiated the activity of the native compound.

Animals↗
PubMedDate not supplied

Axon-myelin transfer of phospholipids and phospholipid precursors. Labeling of myelin phosphoinositides through axonal transport.

Previous studies have provided evidence for axon-to-myelin transfer of intact lipids and lipid precursors for reutilization by myelin enzymes. Several of the lipid constituents of myelin showed significant contralateral/ipsilateral ratios of incorporated radioactivity, indicative of axonal origin, whereas proteins and certain other lipids did not participate in this transfer-reutilization process. The present study will examine the labeling of myelin phosphoinositides by this pathway. Both 32PO4 and [3H]inositol were injected monocularly into 7-9-wk-old rabbits and myelin was isolated 7 or 21 days later from pooled optic tracts and superior colliculi. In total lipids 32P counts of the isolated myelin samples showed significant contralateral/ipsilateral ratios as well as increasing magnitude of contralateral-ipsilateral differences during the time interval. Thin-layer chromatographic isolation of the myelin phosphoinositides revealed significant 32P-labeling of these species, with PIP and PIP2 showing time-related increases. This resembled the labeling pattern of the major phospholipids from rabbit optic system myelin in a previous study and suggested incorporation of axon-derived phosphate by myelin-associated enzymes. The 32P label in PI, on the other hand, remained constant between 7 and 21 days, suggesting transfer of intact lipid. This was supported by the labeling pattern with [3H]inositol, which also showed no increase over time for PI. These results suggest axon-myelin transfer of intact PI followed by myelin-localized incorporation of axon-derived phosphate groups into PIP and PIP2. The general topic of axon-myelin transfer of phospholipids and phospholipid precursors is reviewed.

Animals↗
PubMed1979

Investigation of phospholipid changes in actively metabolizing by high-performance liquid chromatography of 32P-labelled phospholipids.

A high-performance liquid chromatographic system was employed to study turnover rates of phospholipids in various types of cells, such as leukocytes, erythrocytes and yeast cells. In the extracts obtained from 32P-labelled cells ten to twelve different phospholipids could be identified. Phosphatidyl glycerol and other minor phospholipids show a high specific activity, so that the lipids may be readily detected. The reproducibility and sensitivity of the method permits the determination of lipid changes during nutrient uptake, phagocytosis, or other cellular activities.

Animals↗