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PubMed1985

Phospholipid methyltransferase activity in pancreatic islets: activation by calcium.

Pancreatic islet homogenates contain a Mg2+-requiring phospholipid methyltransferase activity, the activity of which was doubled by calcium (K0.5 less than 5 microM). Other divalent metal ions stimulated the activity from 11 to 35%, but zinc and strontium were inhibitory. Cyclic AMP had no effect on the enzyme activity and cyclic GMP inhibited it slightly. Calcium increased the Vmax of the enzyme without affecting its Km with respect to S-adenosylmethionine (6 microM). Chlorpromazine, trifluoperazine, and dibucaine inhibited the calcium-stimulatable activity without affecting the activity in the absence of calcium. Phosphatidylserine stimulated, and arachidonic acid and palmitic acid inhibited, the basal enzyme activity. The methylated products were found to be primarily mono- and dimethylphosphatidylethanolamine (30%) and phosphatidylcholine (43%) and an, as yet unidentified, nonpolar lipid fraction (27%), as judged by thin-layer chromatography. In the presence of calcium, incorporation of methyl groups into phosphatidylcholine, mono- and dimethylphosphatidylethanolamine, and nonpolar lipids was increased by 131, 60, and 46%, respectively. Based on the localization of the enzyme activity in the insulin secretory granule fraction, it is proposed that phospholipid methylation plays a role in coupling the stimulus to the initial events in insulin secretion, leading to the exocytosis of insulin.

Animals↗
PubMed1978

Effect of membrane cholesterol on potassium transport in Mycoplasma mycoides var. Capri (PG3).

Relationships between membrane lipid composition and physiological properties, particularly intracellular potassium levels, have been studied at 37 degrees C in Mycoplasma mycoides var. Capri (PG3). Native organisms grown on medium supplemented with either oleic acid plus palmitic acid or elaidic acid have identical growth characteristics, acidification properties and intracellular K content. On the other hand, when the cholesterol normally present in the membrane (20--25% of total lipids) is reduced to less than 2%, we observe: (1) the intracellular K content decreases (20 microgram K/mg cell protein instead of 40) and is independent of the phase of growth; (2) K passive permeability is drastically increased but K distribution remains in equilibrium with the transmembrane potential (delta psi); (3) organisms stop growing at pH 6.5 (instead of 5.2) and acidification is reduced by 40%, suggesting a large increase in H+ permeability, and (4) intracellular Na contents rise from 3 to 9 microgram Na/mg cell protein. Replenishing cholesterol in membranes of depleted cells results in a recovery of the high intracellular K level (35--40 microgram K/mg cell protein) and acidification properties. It is suggested that cholesterol affects the cation content via the increase in proton permeability which in turn controls the value of the delta psi responsible for the value of intracellular K equilibrium. Changes in K passive permeability, although related to the amount of cholesterol present in the plasma membrane, are probably not involved in the control of the intracellular K level.

Biological Transport↗
PubMed1978

Distribution of radioactivity in myelin lipids following subcutaneous injection of [14C]stearate.

Blood fatty acids are an important parameter for the synthesis of brain myelin as exogenous stearic acid is needed: after subcutaneous injection to 18-day-old mice this labelled stearic acid is transported into brain myelin and incorporated into its lipids. However the acid is partly metabolized in the brain by elongation (thus providing very long chain fatty acids, mainly lignoceric acid) or by degradation to acetate units (utilized for synthesis of medium chain fatty acids as palmitic acid, and cholesterol). These metabolites are further incorporated into myelin lipids. The myelin lipid radioactivity increases up to 3 days; most of the activity is found in phospholipids; their fatty acids are labelled in saturated as well as in polyunsaturated homologues but sphingolipids, especially cerebrosides, contain also large amounts of radioactivity (which is mainly found in very long chain fatty acids, almost all in lignoceric acid). The occurrence of unesterified fatty acids must be pointed out, these molecules unlike other lipids, are found in constant amount (expressed in radioactivity per mg myelin lipid).

Animals↗
PubMed1980

The effect of mouse serum on lipid metabolism in embryonic chick limb-bud cells.

Dissociated embryonic chick limb cells will undergo terminal differentiation in culture. The addition of whole or delipidated mouse serum to the cultures will, however, inhibit the chondrogenic potential of the cells. The inhibitory serum readily stimulates increased incorporation of arachidonic acid and palmitic acid into triacylglycerol in the treated cells, while the incorporation of arachidonate into various phospholipids is significantly lowered. In contrast mouse serum has no effect on the incorporation of inorganic [32P]phosphate into phospholipid. We interpret the patterns of incorporation of these lipid substrates as indicating that mouse serum modulates the deacylation-reacylation cycle of phospholipids (Lands' cycle), which is primarily responsible for the incorporation of arachidonic acid. This finding suggests that there may be a decrease in membrane fluidity which might play a key role in cellular regulation and differentiation.

Animals↗
PubMed1992

Studies on the chemical structure of neutral glycosphingolipids in eggs of the sea hare, Aplysia juliana.

Six neutral glycosphingolipids (GL-1-GL-6) were obtained from eggs of the sea hare (Aplysia juliana) and were characterized by FABMS, 1H-NMR, partial acid hydrolysis, methylation studies and GC analysis of the component sugars, fatty acids and long-chain bases. The following structures were determined to be Glc beta 1-1Cer (89%) and Gal beta 1-1Cer (11%) for GL-1, Glc beta 1-1Cer (47%) and Gal beta 1-1Cer (53%) for GL-2 having hydroxy fatty acids in the ceramide moiety, Gal beta 1-4Glc beta 1-1Cer for GL-3, Fuc alpha 1-2Gal beta 1-4Glc beta 1-1Cer for GL-4, Gal alpha 1-2Gal beta 1-4Glc beta 1-1Cer for GL-5 and GalNAc alpha 1-3(Gal alpha 1-2)Gal beta 1-4Glc beta 1-1Cer for GL-6. The fatty acid composition of each glycosphingolipid, except for GL-2, which contained 2-hydroxypalmitic acid, consisted of mostly saturated C16-C20 acids, especially palmitic acid and stearic acid. The long-chain bases of all glycosphingolipids consisted mainly of branched nonadeca-4-sphingenine and octadeca-4-sphingenine. GL-6, which was one of the major glycosphingolipids, may be a precursor of a series of phosphonoglycosphingolipids which have been isolated from the skin of A. kurodai.

Animals↗
PubMed1993

Biosynthesis of a novel 3-oxo-2-tetradecyloctadecanoate-containing phospholipid by a cell-free extract of Corynebacterium diphtheriae.

We have isolated, purified, and identified by chemical analyses and mass spectrometry, a novel 3-oxo-2-tetradecyloctadecanoate (dehydrocorynomycolate)-containing phospholipid (PL-1) from the chloroform-methanol extract of Corynebacterium diphtheriae. This phospholipid was separated from all of the other known dehydrocorynomycolate and 3-hydroxy-2-tetradecyloctadecanoate (corynomycolate)-containing lipids and found to be unstable even at -20 degrees C. It was present in trace amounts as a homologous series (molecular weights of 1400 and 1404 as the methyl esters) and composed of a dehydrocorynomycolate, a phosphate group, a diacylglycerol, and an unidentified amine-containing component. Because of the complexity of these phospholipids, their complete structural determination is yet to be completed. A cell-free extract of C. diphtheriae catalyzed the incorporation of radiolabel from [14C]palmitic acid into PL-1. This incorporation was ATP-dependent, and the rate was linear with respect to both time and protein concentration. The radiolabel was incorporated primarily into the dehydrocorynomycoloyl moiety of PL-1. While avidin did not show any significant effect, cerulenin showed a marked inhibition of this reaction. Based on these results, we suggest that this dehydrocorynomycolate-containing PL-1 may be the long-sought acyl carrier-containing product of a Claisen-type condensation.

Avidin↗
PubMed1995

Substrate specificity of rat liver mitochondrial carnitine palmitoyl transferase I: evidence against alpha-oxidation of phytanic acid in rat liver mitochondria.

The two branched chain fatty acids pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) and phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) were converted to co-enzyme A thioesters by rat liver mitochondrial outer membranes. However, these branched chain fatty acids could not be converted to pristanoyl and phytanoyl carnitines, respectively, by mitochondrial outer membranes. As expected, the unbranched long chain fatty acids, stearic acid and palmitic acid, were rapidly converted to stearoyl and palmitoyl carnitines, respectively, by mitochondrial outer membranes. These observations indicate that the branched chain fatty acids could not be transported into mitochondria. The data presented strongly suggest that in rat liver, alpha-oxidation of phytanic acid occurs in organelles other than mitochondria.

Animals↗
PubMed1984

Serum-free medium for generation and propagation of functional human cytotoxic and helper T cell clones.

A serum-free lymphocyte culture medium is described in which serum is replaced by bovine serum albumin, transferrin, insulin, ethanolamine and a mixture of saturated and unsaturated fatty acids (linoleic acid, oleic acid and palmitic acid). In this serum-free medium proliferative and cytotoxic responses induced in mixed lymphocyte culture were comparable with those obtained in medium containing serum. Antigen-specific cytotoxic and helper T cells were isolated and could be propagated in serum-free medium without loss of function.

Blood Physiological Phenomena↗
PubMed1985

Glycerolipid formation and PGE2 and PGF2 alpha production of rat renal papillae in vitro, the effects of urea.

The glycerolipid production by rat renal papillary slices varied inversely with the urea concentration (0-1660 mM) whether the production was measured as labelling of the glycerol backbone from glucose or as incorporation of labelled arachidonic acid and palmitic acid. The rate of phospholipid formation was most dependent on medium urea concentrations in the range between 0 and 1100 mM. The production of prostaglandins PGE2 and PGF2 alpha, measured radioimmunologically or by an isotope derivative method was in the same range inversely related to the production of glycerolipids and chain elongations. The effect of urea on prostaglandin formation is probably indirectly caused by the inhibition of the phospholipid formation and chain elongation, since the effect was abolished by 1% defatted albumin in the medium. The data suggest that the level of free arachidonic acid within the cells is controlled to an important extent by glycerolipid formation and chain elongation.

Adult↗
PubMed1995

Enhancement of rotavirus infectivity by saturated fatty acids.

The effect of different saturated fatty acids from 10 to 16 carbon atom chains and some derivatives on the infectivity of SA-11 rotavirus was examined. Both fatty acids and derivatives induced an increase of rotavirus infected LLC-MK2 cells when present during viral absorption to host cells. Capric acid and palmitic acid were the most effective with a dose-dependent relationship. These last lipids, in the same experimental conditions, failed to restore the susceptibility to infection of LLC-MK2 cells made resistant by neuraminidase treatment or to allow cell infection by non-infectious single-shelled viral particles. Results obtained suggest that the enhancing effect on viral infectivity by saturated fatty acids requires previous binding of rotaviral outer capsid proteins to sialic acid containing cell receptors.

Animals↗
PubMed1989

Evidence of Ca2+ mobilizing action of arachidonic acid in human platelets.

The addition of arachidonic acid induced a rapid release of 45Ca2+ from human platelet membrane vesicles which accumulated 45Ca2+ in the presence of ATP. Docosahexaenoic acid, eicosapentaenoic acid, linolenic acid and linoleic acid were less active than arachidonic acid. In contrast, oleic acid, myristic acid and palmitic acid were without effect. The thromboxane A2 analogue induced no 45Ca2+ release. The cyclooxygenase/lipoxygenase inhibitor failed to suppress arachidonic acid-induced 45Ca2+ release at the concentration which inhibited the production of lipid peroxides. These data indicate that the activity of arachidonic acid may be due to fatty acid itself and not to its metabolites. The combination of arachidonic acid and inositol 1,4,5-trisphosphate (IP3) resulted in a greater 45Ca2+ release from platelet membrane vesicles than either compound alone. When the intracellular free Ca2+ concentration ([Ca2+]i) was measured using fura-2, the thrombin-induced [Ca2+]i increase was reduced in platelets which had been treated with a phospholipase A2 inhibitor, ONO-RS-082 (2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid). These results provide evidence that arachidonic acid alone may cause Ca2+ increase and also may induce an additional Ca2+ mobilization to IP3-induced Ca2+ release in human platelets.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1993

Fatty acid modulation of cytokine release from human monocytic cells.

The effect of individual fatty acids on the release of interleukin-1-like (IL-1-like) cytokine activity was investigated on human monocytic cells, primarily the cell line U937 and also peripheral blood monocytes. IL-1-like bioactivity was estimated by assessing the effect of supernatants from monocytic cells on the proliferation of thymocytes as measured by [3H]thymidine incorporation into the acid insoluble fraction of the thymocytes. A pronounced concentration-dependent increase (in the range 1-100 microM) in the release of IL-1-like activity was observed with arachidonic acid, dihomo-gamma-linolenic acid (DGLA) and eicosapentaenoic acid (EPA) in absence and presence of bacterial endotoxin (LPS). A much less pronounced concentration-dependent increase in the release of IL-1-like activity was observed with oleic acid and linoleic acid had only a small effect at 100 microM. The potencies of each fatty for this effect using the EC50 concentrations were arachidonic acid > EPA > or = DGLA > linoleic acid > oleic acid with palmitic acid having no effect. The IL-1-like activity was confirmed by the attenuation of the monocytic-cell-supernatant-induced increase in thymocyte proliferation by anti-IL-1 beta antiserum. An increase in the release of anti-IL-1 beta-antiserum-precipitable radioactivity from U937 cells prelabelled with [35S]methionine then incubated with fatty acids in the presence of LPS further confirmed that IL-1 release was increased. Arachidonic acid and EPA also increased the release of IL-1-like activity from peripheral blood monocytes demonstrating that normal monocytes can respond in a similar manner and that this effect of the fatty acids is not restricted to the U937 cell line.

Arachidonic Acid↗
PubMed1984

Studies on the metabolic fate of sucrose esters in rats.

The metabolism in rats of sucrose esters of stearic acid and palmitic acid was studied in vivo and in vitro using esters labelled with 14C at the sucrose of fatty-acid moiety. In excretion studies, the ratio of expired radioactivity to absorbed radioactivity after oral administration of the sucrose esters labelled at the sucrose moiety was similar to that after the administration of [14C]sucrose. A similar correlation between the ester labelled at the fatty-acid moiety and the free [14C]fatty acid was also observed. No intact sucrose ester was detected in the urine. Studies in vitro using everted intestinal sacs showed that there was virtually no transport of 14C-labelled sucrose esters from the mucosal to the serosal solution through the intestinal tissues, and that the enzymes in the intestinal mucosa played a more important role in the hydrolysis of sucrose esters than did those in the digestive fluid. In studies of intestinal absorption through the mesenteric lymphatic system, during the 24 hr after ingestion 1.8% of the administered radioactivity was recovered in the lymph after dosing with [U-14C]sucrose monostearate whereas 20% was recovered in the lymph after dosing with sucrose [1-14C]monostearate. This difference in levels of recovery of administered radioactivity indicated that sucrose monostearate was absorbed only after hydrolysis. No intact ester was detected in the lymph or in the portal or femoral blood. The results of all of these experiments show that the sucrose esters are hydrolysed to sucrose and fatty acids prior to intestinal absorption.

Absorption↗
PubMed1981

Comparison of the oxidation of glutamine, glucose, ketone bodies and fatty acids by human diploid fibroblasts.

The contribution of glutamine, glucose, ketone bodies and fatty acids to the oxidative energy metabolism of human diploid fibroblasts ws studied. The rate of glutamine oxidation by fibroblasts was 98 nmol/h per mg cell protein compared to 2 nmol/h per mg cell protein or less for glucose, acetoacetate, D-3-hydroxybutyrate, octanoic acid and palmitic acid. Glucose inhibited glutamine oxidation by 85%, while the other substrates had no effect. Therefore, these cells meet their energy requirement almost solely by anaerobic glycolysis and glutamine oxidation.

Cell Line↗
PubMed1995

Bile formation and hepatic plasma membrane composition in guinea-pigs and rats.

We compared bile formation, and biliary and liver plasma membrane composition in guinea-pigs and rats in an attempt to explain the observation that the bile flow rate and the bile acid independent fraction of bile flow (BAIF) in guinea-pigs is about five to seven times higher than in rats. Analysis of electrolytes in bile showed that bicarbonate was significantly [acid] higher in guinea-pigs while Cl-, phosphate and Ca2+ were markedly lower than in rats. High bile independent secretion in guinea-pigs was associated with a significantly lower concentration of total bile acid, phospholipid and cholesterol than in rats. Bile acid distribution studies showed that glycine conjugated chenodeoxycholate and ketolithocholate were the main bile acids in guinea-pigs, while taurine conjugated cholate and muricholate were the predominant bile acids in rats. Total fatty acid analysis of bile indicated that in rats the major fatty acids were palmitic acid (C16:0) and linoleic acid (C18:2, n-6). In guinea-pigs, the contribution of these fatty acids was lower than in rats and compensated with a significantly higher percentage of oleic acid (C18:1, n-9). Concentrations of anionic polypeptide fraction (APF), an acidic calcium binding apoprotein closely associated with biliary phospholipid and cholesterol secretion was also significantly lower in guinea-pigs. Canalicular plasma membrane analysis showed that as compared with rats, specific activities of Na+,K+ ATPase, and cholesterol and phospholipid content were markedly lower in guinea-pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1993

2-(4-Hydrazinocarbonylphenyl)-4,5-diphenylimidazole as a versatile fluorescent derivatization reagent for the high-performance liquid chromatographic analysis of free fatty acids.

A new fluorescent derivatization reagent with a lophine skeleton, 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI), has been synthesized and applied to the assay of saturated free fatty acids. The HCPI derivatives with five representative saturated fatty acids [caproic acid (C6), lauric acid (C12), palmitic acid (C16), stearic acid (C18) and arachidic acid (C20)] were synthesized to examine their fluorescence properties. The fluorescence spectra (lambda ex ca. 335 nm, lambda em ca. 455 nm) of the derivatives were almost identical in methanol, n-heptane and acetonitrile. For the high-performance liquid chromatographic assay, fatty acids were derivatized with HCPI using a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and pyridine at room temperature. The HCPI derivatives were separated on a C18 column with a gradient elution of methanol-water, and the eluates were monitored at 455 nm using an excitation wavelength of 335 nm. By this method, seven kinds of free fatty acid (C6, C10, C12, C14, C16, C18 and C20) could be determined using margaric acid (C17) as an internal standard. Calibration curves were linear over the range 0.2-400 pmol per 20-microliters injection (r = 0.994-1.000). Relative standard deviations of the peak-height ratio for five replicate measurements of fatty acids (100 pmol per injection) were 0.7-2.6%. Detection limits were 7-57 fmol at a signal-to-noise ratio of 3. The method could be successfully applied to the determination of four saturated fatty acids (C12, C14, C16 and C18) in normal human serum.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Effect of age on the fatty acid composition of phospholipids in human lymphocytes.

We have examined the fatty acid composition of phospholipids of unstimulated and PHA-stimulated T cells from young and old donors. Our results demonstrate that aging is accompanied by decreases in the saturated fatty acids, myristic acid, and palmitic acid, and a concomitant increase in the unsaturated arachidonic acid. Following activation with PHA for 24 h, age-associated differences in fatty acids could no longer be detected. In contrast to the lymphocyte, aging did not affect the fatty acid composition of either serum or neutrophil phospholipids. Exposure of lymphocytes from old donors to myristic acid complexed medium increased the levels of myristate in the phospholipids to levels similar to that seen in lymphocytes from young donors. We conclude from these studies that aging is accompanied by an alteration in the fatty acid profiles of phospholipids, and that incubation in myristic acid complexed medium modulates these profiles. These alterations are unique to lymphocytes and may contribute to the age-related declines in lymphocyte function.

Adult↗
PubMed2005

Characterization of a cDNA encoding Arabidopsis secretory phospholipase A2-alpha, an enzyme that generates bioactive lysophospholipids and free fatty acids.

Phospholipase A2s (PLA2s) are enzymes that liberate lysophospholipids and free fatty acids (FFAs) from membrane phospholipids in response to hormones and other external stimuli. This report describes the cloning and functional characterization of a PLA2 cDNA from Arabidopsis thaliana, AtsPLA2-alpha, which represents one of four secretory PLA2 (sPLA2) genes in Arabidopsis. The encoded protein is 148-amino acid polypeptide and is predicted to contain a 20-amino acid signal peptide at its amino terminus. The predicted mature form (Mr=14,169) of AtsPLA2-alpha exhibited approximately 5 times the specific activity of its pre-processed form. Different from animal sPLA2s, AtsPLA2-alpha showed a significant preference for the acyl group linoleic acid over palmitic acid in phospholipid hydrolysis. Like some animal sPLA2s, however, it has a slight preference for phosphatidylethanolamine over phosphatidylcholine as the substrate. The specific activity of AtsPLA2-alpha continuously increased as the Ca2+ concentration was increased to 10 mM, and the optimal pH range was very broad and biphasic between 6 and 11. AtsPLA2-alpha transcript was detected at low levels in roots, stems, leaves, and flowers but not in siliques.

Amino Acid Sequence↗