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PubMed1977

Chemical proof of lipid-protein interactions by crosslinking photosensitive lipids to apoproteins. Intermolecular cross-linkage between high-density apolipoprotein A-I and lecithins and sphingomyelins.

The molecular interactions and spatial arrangements of phospholipids and apoproteins of human high-density lipoprotein were studied by a chemical approach. Phosphatidylcholines and sphingomyelins substituted with fatty acyl residues of high specific radioactivity and labelled with the photosensitive azido group in specific positions were prepared by chemical synthesis. They were recombined with apolipoprotein A-I of human serum high density lipoprotein. The lipoprotein complexes containing either azido lecithins or azidosphingo-myelins were purified by agarose chromatography from excess lipids. The irradiation was performed under conditions which prohibit the interference with the apoprotein structure as proven by circular dichroism, fluorescence spectroscopy, immunodiffusion test and disc electrophoresis. Non-covalently bound lipid molecules were removed by Sephadex LH 20 chromatography. Mild alkaline treatment liberated radioactive fatty acids which were not directly linked to the polypeptide chain, but rather via neighbouring phospholipid molecules. The lipoprotein appeared as a single radioactive band in dodecylsulfate polyacrylamide gel electrophoresis as seen by radioscanning, which further proved the covalent linkage of the fatty acyl residues to the polypeptide chain. In the immunodiffusion test, there is no difference between covalently crosslinked phospholipid-apoLp A-I complex and the non-photolyticall treated complex. This is the first chemical proof of the spatial relationship of the hydrophobic side chains of the lipid and polypeptide chains in a lipoprotein complex.

Apolipoproteins↗
PubMed1975

Z protein in hepatic uptake and esterification of long-chain fatty acids.

Fatty acids radioactivity was bound to Z protein in liver after administration of['3H]oleate to rats or to a perfused rat liver preparation. Pretreatment withflavaspidic acid (340 mumol/kg), a potent inhibitor of fatty acid binding to hepatic Zprotein in vitri, effectively reduced oleate radioactivity bound to Z by 90.2 plusor minus 4.3% and 85.0 plus or minus 6.2% in the intact rat and perfused liver, respectively. In spite of this effect, pretreatment of rats with flavaspidic acid did notalter plasma clearance, hepatic uptake, and esterification of ['3H]oleate. In contrast, in the perfused liver preparation, infusion of flavaspidic acid (340 mumol/kg)or bromosulphalein (360 mumol/kg) increased uptake of ['3H]oleate at least twofold,and oleate esterification was decreased by 15-30%. These results suggest that the binding of long-chain fatty acids to Z protein is not an obligatory step in their uptakeby the liver and that Z protein may be involved in fatty acid esterification.

Animals↗
PubMed1976

[Changes in the erythrocyte membrane during blood preservation. Influence of progesterone].

Modifications of the erythrocyte membrane during blood conservation are studied. The functional condition of the membrane was observed by means of the biosynthesis of lecithines; modifications occurring at the level of the composition of the membrane proteins were then looked for. The study has been carried out on fresh blood and on blood stroed for 8 days, 15 days, 29 days and 43 days. Another series of assays has been done on stored blood in the presence of progesterone after the same conservation periods. The metabolic activity of the membrane, in the lecithine biosynthesis is studied by measuring the incorporation of fatty acid in the lysolecithines when the membrane is incubated in the presence of linoleic acid or [14] palmitic acid and coenzyme A, or in the presence of [14C] palmitoyl coenzyme A. Variations have been observed during blood conservation: the incorporation or radioactive fatty acid increases during the first 15 days of conservation, then it decreases to a value nearing the original value after 43 days. When the blood is stored in the presence of progesterone (1,6 mumole/1) a more stable incorporation of the fatty acid is observed; variations during conservation are weaker than without progesterone. Membrane proteins have been studied by electrophoresis on polyacrylamide gel after solubilisation by sodium dodecyl sulfate. The intensity of protein zones after coloring, decreases during conservation especially in proteins with a high molecular weight. A quantitative study has been made by chromatography on Sephadex G200 of dansylated proteins with a fluorimetric dosage. In the presence of progesterone, the decrease of the rate of proteins with a high molecular weight is weaker. Therefore, progesterone is proved to allow a better conservation of erythrocyte membrane proteins. As a conclurion, the results of these works show a positive action of progesterone on the erythrocyte membrane during blood conservation.

Blood Preservation↗
PubMed1998

Mycoplasma penetrans infection of Molt-3 lymphocytes induces changes in the lipid composition of host cells.

The AIDS-associated Mycoplasma penetrans is capable of inducing its own uptake by non-phagocytic cells. The ability of M. penetrans to both adhere to and invade Molt-3 lymphocytes was markedly increased in the presence of polyethylene glycol 8000 (PEG). The effect of PEG was more pronounced in the more alkaline pH range, where the binding kinetics were much faster and almost unaffected by temperature (4-37 degrees C). Incubation of [14C]oleic-acid-labelled Molt-3 cells with viable M. penetrans resulted in a substantial release of radioactive fatty acids, whereas treating the host cells with heat-inactivated mycoplasmas, isolated M. penetrans membrane preparations, or M. penetrans growth medium, had no effect. Total lipid analysis of Molt-3 lymphocytes infected by M. penetrans revealed an augmented level of the neutral lipid fraction that was associated with a decrease in the relative amounts of polar lipids, mainly a decrease in the amount of phosphatidylserine and diphosphatidylglycerol. Analysis of the neutral lipid fraction in the infected Molt-3 cells revealed a fivefold increase in the relative amount of diacylglycerol and a marked increase in the free fatty acid (FFA) fraction. The profile of the FFAs released was dominated by a relatively high concentration of the polyunsaturated fatty acid docosahexaenoic acid. The release of lipid intermediates suggests that the degradation of Molt-3 cell phospholipids induced by M. penetrans may initiate a signal transmission cascade in the host cell.

Fatty Acids, Nonesterified↗
PubMedDate not supplied

Uptake and metabolic conversion of saturated and unsaturated fatty acids in Hep2 human larynx tumor cells.

Research on fatty acid metabolism in cultured human larynx tumor cells Hep2 was carried out. The cells were incubated with either a saturated (palmitic) or a polyunsaturated (linoleic, alpha-linolenic and eicosatrienoic (n-6)) radioactive fatty acid (0.66 pM, 24 h). The best incorporation capacity was observed in the linoleic acid followed by alpha-linolenic, palmitic and eicosatrienoic acids. All fatty acids tested were anabolized to higher derivatives within their own family. Palmitic acid was primarily monodesaturated rather than elongated, proving to have a very active A9 desaturase activity. With respect to polyunsaturated acid metabolism, the conversion of alpha-linolenic acid to higher homologs, although better than linoleic acid, occurred far less efficiently than that observed in other non-highly undifferentiated human tumor cells. This impairment in higher polyunsaturated fatty acid biosynthesis, reflected in the low levels of arachidonic acid in the fatty acid composition, would not reside in the A5 desaturation step since Hep2 cells can readily convert eicosatrienoic acid into arachidonic acid. Considering the potential regulatory role of specific polyunsaturated fatty acids in the cell proliferative control, the knowledge of the metabolism of fatty acids in this human tumor cell would be important for designing future experiments in order to clarify the mechanism involved in balance, proliferation and cell death.

Carcinoma, Hepatocellular↗
PubMed1974

Lipid biosynthesis in green leaves of developing maize.

Successive leaf sections from the base to the tip of rapidly developing leaves of 7-day-old maize (Zea mays var. Kelvedon Glory), grown in the light, utilized acetate for fatty acid biosynthesis in a very divergent manner. Basal regions of the leaf containing proplastids synthesized insignificant proportions of unsaturated fatty acids and appreciable proportions of fatty acids with 20 or more carbon atoms. An increase in the light intensity during incubations with acetate-1-(14)C resulted in very little enhancement of either total or polyunsaturated fatty acid biosynthesis in this tissue.When the distal leaf sections, containing mesophyll chloroplasts with well developed grana and bundle sheath chloroplasts without grana, were incubated with acetate at 150 ft-c and 30 C, approximately 30% of the newly synthesized fatty acids were unsaturated (mainly 18: 1 and 18: 2). At 2800 ft-c and 20 C, 60% of the fatty acids were unsaturated and the total synthesis of fatty acids increased 4-fold. No detectable amount of fatty acids with 20 or more carbon atoms were synthesized in this morphologically mature tissue, and the proportions of newly synthesized fatty acids more closely resembled the endogenous fatty acids in the immature tissue.Only 4% of the newly synthesized fatty acids were 18: 3 but most of this was incorporated into monogalactolipid. In the distal sections, 20 to 25% of the newly synthesized fatty acids in monogalactolipid were 18: 3 compared with the endogenous proportions of 85%. The differences in the composition of the newly synthesized fatty acids and the endogenous fatty acids appear to be related very largely to the low rate of 18: 3 biosynthesis from 18: 1 and 18: 2. Phosphatidyl choline and phosphatidyl ethanolamine, with lower proportions of 18: 3, contained radioactive fatty acids which resembled the endogenous composition more closely.Phosphatidyl choline was quantitatively the most important acyl lipid synthesized under both light conditions. In addition, there was considerable stimulation of acetate incorporation into phosphatidyl glycerol and monogalactolipid, especially in the morphologically most mature regions of the tissue at the higher light intensity.

Journal Article↗
PubMed1980

Effect of gluconeogenic substrates on ketogenesis in isolated rat hepatocytes. I. Effect of glycerol.

The effect of glycerol on the rate of free fatty acids in isolated hepatocytes from starved rats has been studied. 5 mM glycerol inhibited the ketone bodies production from endogenous substrates, acetate, octanoate or oleate. The incorporation of radioactivity into ketone bodies from acetate, octanoate or oleate was also inhibited by glycerol. The oxidation of radioactive fatty acids to CO2 was not significantly changed by glycerol. However, the incorporation of acetate, octanoate or oleate carbons into liver lipids were increased by glycerol.

Acetates↗
PubMed1981

Antiketogenic effect of gluconeogenic substrates. II. Effect of pyruvate.

The effect of pyruvate on the fate of free fatty acids in isolated hepatocytes from starved rats has been studied. 5 mM pyruvate inhibited ketone bodies production variously from endogenous substrates, acetate, octanoate and oleate. However, the incorporation of radioactivity into ketone bodies from acetate, octanoate or oleate was not affected by the presence of pyruvate. The oxidation of radioactive fatty acids to CO2 was increased by the presence of pyruvate. These results suggest that pyruvate inhibited ketogenesis by increasing the rate of the tricarboxylic acid cycle.

Animals↗
PubMedDate not supplied

Conversion of acetate to CO2, lipids, proteins, and lipoproteins during hemodialysis in humans.

Acetate-1-14C or acetate-2-14C was infused into the venous dialysis line in 17 chronic stable patients over a 4-hr period of standard hemodialysis. Radioactive CO2 in expired air was measured continuously during dialysis and for 20 hr postdialysis. Significantly more acetate-1-14C (56 +/- 2%) was recovered as 14CO2 in the expired air than was acetate-2-14C (49 +/- 3%). A total of 81% and 71% of the radioactivity was recovered from the expired air and expended dialysate from acetate-1-14C and acetate-2-14C, respectively. Of the remainder, a significant portion was incorporated into plasma lipids and proteins. Incorporation of radioactivity into phospholipids, cholesterol esters, and triglycerides increased during dialysis and continued to increase during the postdialysis period. Free fatty acid radioactivity increased during dialysis but declined afterwards. In the lipoprotein fractions radioactivities remained elevated at 24 hr in the LDL and HDL fractions, but declined in the VLDLs after this time interval.

Acetates↗
PubMed1969

Localization of the oxidative defect in phytanic acid degradation in patients with Refsum's disease.

The rate of oxidation of phytanic acid-U-(14)C to (14)CO(2) in three patients with Refsum's disease was less than 5% of that found in normal volunteers. In contrast, the rate of oxidation of alpha-hydroxyphytanic acid-U-(14)C and of pristanic acid-U-(14)C to (14)CO(2), studied in two patients, while somewhat less than that in normal controls, was not grossly impaired. These studies support the conclusion that the defect in phytanic acid oxidation in Refsum's disease is located in the first step of phytanic acid degradation, that is, in the alpha oxidation step leading to formation of alpha-hydroxyphytanic acid. The initial rate of disappearance of plasma free fatty acid radioactivity after intravenous injection of phytanic acid-U-(14)C (t(1/2) = 5.9 min) was slower than that seen with pristanic acid-U-(14)C (t(1/2) = 2.7 min) or palmitic acid-1-(14)C (t(1/2) = 2.5 min). There were no differences between patients and normal controls in these initial rates of free fatty acid disappearance for any of the three substrates tested. There was no detectable lipid radioactivity found in the plasma 7 days after the injection of palmitic acid-1-(14)C or pristanic acid-U-(14)C in either patients or controls. After injection of phytanic acid-U-(14)C, however, the two patients showed only a very slow decline in plasma lipid radioactivity (estimated t(1/2) = 35 days), in contrast to the normals who had no detectable radioactivity after 2 days. Incorporation of radioactivity from phytanic acid-U-(14)C into the major lipid ester classes of plasma was studied in one of the patients; triglycerides accounted for by far the largest fraction of the total present between 1 and 4 hr.

Carbon Dioxide↗
PubMed1991

Hydrolysis of chylomicron polyenoic fatty acid esters with lipoprotein lipase and hepatic lipase.

The lipolysis of rat chylomicron polyenoic fatty acid esters with bovine milk lipoprotein lipase and human hepatic lipase was examined in vitro. Chylomicrons obtained after feeding fish oil or soy bean oil emulsions were used as substrates. The lipolysis was followed by gas chromatography or by using chylomicrons containing radioactive fatty acids. Lipoprotein lipase hydrolyzed eicosapentaenoic (20:5) and arachidonic acid (20:4) esters at a slower rate than the C14-C18 acid esters. More 20:5 and 20:4 thus accumulated in remaining tri- and diacylglycerols. Eicosatrienoic, docosatrienoic and docosahexanoic acids exhibited an intermediate lipolysis pattern. When added together with lipoprotein lipase, hepatic lipase increased the rate of lipolysis of 20:5 and 20:4 esters of both tri- and diacylglycerols. Addition of NaCl (final concentration 1 M) during the course of lipolysis inhibited lipoprotein lipase as well as the enhancing effect of hepatic lipase on triacylglycerol lipolysis. Hepatic lipase however, hydrolyzed diacylglycerol that had already been formed. Chylomicron 20:4 and 20:5 esters thus exhibit a relative resistance to lipoprotein lipase. It is suggested that the tri- and diacylglycerol species containing these fatty acids may accumulate at the surface of the remnant particles and act as substrate for hepatic lipase during a concerted action of this enzyme and lipoprotein lipase.

Animals↗
PubMed1985

The physiological role of oxygen-sensitive pyruvate dehydrogenase in mitochondrial fatty acid synthesis in Euglena gracilis.

In Euglena gracilis a malonyl-CoA-independent fatty acid-synthetic system, in which fatty acids are synthesized directly from acetyl-CoA as both primer and C2 donor, occurs in mitochondria, and the system contributes to the wax ester fermentation. The activity of fatty acid synthesis in the mitochondrial system was enhanced about six times when an artificial acetyl-CoA-regenerating system was present, indicating that the fatty acid-synthetic activity is controlled by the ratio of acetyl-CoA against CoA. When fatty acids were synthesized using pyruvate instead of acetyl-CoA as substrate, a high activity, about 30 times higher than that from acetyl-CoA, was found under anaerobic conditions (below 10(-5) M oxygen), while in aerobiosis fatty acids were not synthesized at all. CoA, NADH, and NADP+ were required as cofactors for fatty acid synthesis from pyruvate. It was indicated that high activity of fatty acid synthesis from pyruvate due to the high ratio of acetyl-CoA against CoA was maintained by the action of the oxygen-sensitive pyruvate dehydrogenase found in Euglena mitochondria. When [2-14C]pyruvate was fed into intact mitochondria under anaerobic conditions, radioactive fatty acids were formed in the presence of malate, which provided reducing power for the matrix.

Acetyl Coenzyme A↗
PubMed1982

Diffusion of intracerebrally injected [1-14C]arachidonic acid and [2-3H]glycerol in the mouse brain. Effects of ischemia and electroconvulsive shock.

[2-3H]Glycerol and [1-14C]arachidonic acid were injected into the region of the frontal horn of the left ventricle of mice and were distributed rapidly throughout the brain. After 10 sec, most of the radioactive fatty acid was found in the hemisphere near the injection site; after 10 min, it was recovered in similar proportions in the cerebellum and brain stem. [2-3H]Glycerol showed a heterogeneous distribution, with most of the label remaining in the left hemisphere even after 10 min. On a fresh weight basis, cerebrum, cerebellum, and brain stem were found to contain similar amounts of labeled glycerol. However, the amount of [1-14C]arachidonate in cerebrum was only 50% of that recovered from cerebellum or brain stem. Brain ischemia or a single electroconvulsive shock reduced the spread of the label, producing an accumulation of radioactivity in the injected hemisphere, except for an increase in [2-3H]glycerol in the brain stem during ischemia. Despite the significant decrease in available precursor in the cerebellum and brain stem after electroshock, the amount of label incorporated into lipids was not altered in these areas and only slightly diminished in the cerebrum.

Animals↗
PubMed1995

Immunoprecipitation of a phospholipase D activity with antiphosphotyrosine antibodies.

When granulocyte-macrophage colony-stimulating factor (GM-CSF)-treated human neutrophils were challenged with the chemotactic factor fMet-Leu-Phe, it was possible to detect a time-dependent increase in the hydrolytic (as measured by the production of phosphatidic acid, PA) and the transphosphatidylation (as measured by the production of phosphatidylethanol, PEt) activities of phospholipase D in intact cells prelabeled with a radioactive fatty acid. Both activities were inhibited by preincubation of cells with genistein. Appropriate conditions were developed to test the PLD transphosphatidylation activity against exogenous phosphatidylcholine (PCho) in an in vitro system. As in intact cells, increased PLD activity could be detected in cell lysates obtained from fMet-Leu-Phe-treated cells compared with controls. When lysates were immunoprecipitated with antiphosphotyrosine antibodies, a PLD activity was found only in immune complexes that were prepared from fMet-Leu-Phe-treated cells. Conversely, no activity was found in lysates immunoprecipitated with an irrelevant antibody (GTPase-activating protein, GAP) that nevertheless was able to recognize a tyrosylphosphorylated form of GAP, as demonstrated by western blotting. These data suggest that a PCho-PLD, or a tightly bound protein, is tyrosine phosphorylated during cell activation.

Antibodies, Monoclonal↗
PubMed2000

Triacylglycerols of the red microalga Porphyridium cruentum can contribute to the biosynthesis of eukaryotic galactolipids.

A mutant of the red microalga Porphyridium cruentum was selected on the basis of impaired growth at suboptimal temperatures (15 vs. 25 degrees C). Fatty acid and lipid analyses revealed diminished proportions of eicosapentaenoic acid (from 41 to 30%) and of the eukaryotic molecular species (from 38 to 28% of monogalactosyldiacylglycerol (MGDG) and elevated proportion (10 vs. 2%) of triacylglycerols (TAG) in the mutant, as compared with the wild type. Pulse labeling of the wild type cells with radioactive fatty acid precursors indicated an initial incorporation of the fatty acids into phosphatidylcholine (PC) and TAG. Following the pulse, the label of PC and TAG decreased with time (from 25 to 5% of the total dpm in TAG) while that of chloroplastic polar lipids, mainly MGDG, continued to increase. In the mutant, however, the labeling of TAG after the pulse was higher (30% of the total dpm) than that of the wild type and decreased only slightly to 20%. This may indicate that in P. cruentum, TAG can contribute to the biosynthesis of eukaryotic species of MGDG.

Chlorophyll↗
PubMed1993

Biosynthesis of vernoleate (cis-12-epoxyoctadeca-cis-9-enoate) in microsomal preparations from developing endosperm of Euphorbia lagascae.

Epoxidated fatty acids are the major constituents of the triacylglycerols in a few plant species. We have investigated the biosynthesis of vernolic acid (cis-12-epoxyoctadeca-cis-9-enoic acid) in the seed oil of Euphorbia lagascae. Microsomes were isolated from developing endosperm. The membrane lipids were labeled in situ with [14C]oleate or [14C]linoleate, which mainly were recovered in phosphatidylcholine (PC), and the metabolization of the radioactive fatty acids was followed in incubations with or without NADPH. In the presence of NADPH, [14C]vernoleate was formed. After short incubations, most of the vernolic acid was found in PC, but with increasing incubation times, the free acid dominated. The synthesis of vernoleate was inhibited by carbon monoxide, but not by cyanide. The presence of anticytochrome b5 antibodies inhibited both the desaturation of [14C]oleate to [14C]linoleate and the epoxidation of [14C]linoleate to [14C]vernoleate. Free linoleic acid did not serve as substrate for epoxidation. The results indicate that, in the endosperm of E. lagascae, vernoleate is synthesized on PC from linoleate, and that the epoxidation is catalyzed by a cytochrome P450 and involves cytochrome b5.

Epoxy Compounds↗