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1.
Phospholipase A2, which is linked to a protein kinase C pathway, hydrolyzes phosphatidylcholine into cis-unsaturated free fatty acids and lysophosphatidylcholine (lysoPC). The present study investigated the effect of the free fatty acids, such as arachidonic, oleic, linoleic, and linolenic acid, and lysoPC on neurotransmission by monitoring population spikes (PSs) from the granular cell layer of rat hippocampal slices. All the free fatty acids and lysoPC examined here gradually increased PS amplitude to a different extent, the effect being evident 60 min after treatment. No significant synergistic enhancement in the PS amplitude was not induced by arachidonic acid following oleic acid, linoleic acid or lysoPC. The results of the present study, thus, demonstrate that phospholipase A2-linked free fatty acids and lysoPC are employed in the sustained facilitation of hippocampal neurotransmission, suggesting a significant role of a phospholipase A2 signaling pathway in the neuroplasticity. 相似文献
2.
Phaseolus vulgaris mitochondria incubated in sucrose swell rapidly upon the addition of phospholipase A. Bovine serum albumin inhibits the swelling. The release of free fatty acids as a result of phospholipase A action on the mitochondria is detected only in the presence of bovine serum albumin, which promotes the hydrolysis of both mitochondrial phospholipids and purified lecithin. Either free fatty acid or lysolecithin is able to initiate an extensive mitochondrial swelling in sucrose. It is suggested that phospholipase A-induced swelling results from the release of lysophosphatides plus free fatty acids and their subsequent detergent action on the membranes rather than phospholipid loss per se. 相似文献
3.
Endogenous suppression of neutral-active and calcium-dependent phospholipase A2 in human polymorphonuclear leukocytes 总被引:6,自引:0,他引:6
Phospholipase A2 activity was measured in homogenized and acid-extracted human polymorphonuclear leukocytes using [1-14C]oleate-labelled autoclaved Escherichia coli as substrate. In whole homogenate and in the supernatant and particular fractions separated by centrifugation at 150,000 X g, phospholipase activity was barely detectable (1-4 pmol/h per 10(6) cell equivalents). By contrast, acid extracts of these fractions contained over 10-times as much phospholipase activity in the dialyzed supernatants (20-300 pmol/h per 10(6) cell equivalents), whereas phospholipase inhibitor(s) were found in the sediment. The acid-solubilized phospholipase A2 activity was absolutely Ca2+-dependent and optimal at pH 7.0-7.5 with 1.0 mM added Ca2+. Addition of the resuspended sediment of the acid extract dose-dependently suppressed phospholipase activity in the supernatant; less than equivalent amounts were sufficient to inhibit 95%. Suppressor activity was lipid-extractable. After thin layer chromatography of lipid extracts, the bulk of inhibitory activity was recovered from the free fatty acid region. Analysis of the fatty acids by gas liquid chromatography showed that 63% were unsaturated. All unsaturated fatty acids tested were potent inhibitors of phospholipase A2 activity (IC50 3-10 microM). Oleoyl-CoA, hydroxyeicosatetraenoic acids and leukotriene D4 were also inhibitory, while methyl oleate, saturated fatty acids and the prostaglandins E2 and F2 alpha had no effect. These in vitro data indicate that neutral-active and calcium-dependent phospholipase A2 in human polymorphonuclear leukocytes is largely suppressed by endogenous inhibitors and suggest that unsaturated fatty acids and some of their metabolites may partly account for this suppressor activity. 相似文献
4.
The effect of calmodulin antagonists on the amounts of free fatty acids produced by rabbit alveolar macrophages was determined by fluorometric high-performance liquid chromatography. Opsonized zymosan-induced arachidonic acid production was dramatically suppressed in the presence of W-7 and trifluoperazine without an effect on the production of other fatty acids. Calmodulin antagonists inhibited phospholipase A and abolished the release of arachidonic acid from phospholipids. The present results suggest that a zymosan-sensitive pool of 20:4, which is different from that of other fatty acids, is present in macrophages and that calmodulin antagonists selectively inhibit phospholipase A, which preferentially degrades phospholipids with 20:4. 相似文献
5.
The lysosomal subcellular fraction of rat liver contains acid hydrolases which can carry out the degradation of cardiolipin to yield water-soluble products and free fatty acids. The time course of appearance of the products indicates that the major catabolic route involves the sequential removal of three of the fatty acids, followed by hydrolysis to acylglycerophosphoryl glycerol (from which the fatty acid is subsequently removed) and d-glycerophosphate (which is hydrolysed to give free phosphate and glycerol). The phospholipase A activity responsible for removal of the first fatty acid is located in the lysosomal fraction. 相似文献
6.
Evidence for and subcellular localization of a ca-stimulated phospholipase d from maize roots 总被引:1,自引:1,他引:0
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Autolytic lipid changes in corn (Zea mays L.) root crude homogenates and isolated membranes were examined by the use of high performance thin-layer chromatography. In the absence of added CaCl2, losses in phosphatidylcholine and other phospholipids corresponds to increase in fatty acids without the accumulation of either phosphatidic acid or lyso-phosphatidylcholine. However, in the presence of 1 millimolar CaCl2, phosphatidylcholine concentrations declined more rapidly with an immediate increase in phoshatidic acid, and slower rate of fatty acid accumulation. Autolytic phospholipid degradation yielded primarily free fatty acids in the absence of Ca and phosphatidic acid in the presence of 1 millimolar CaCl2, suggesting the presence of an acyl hydrolase and phospholipase D activities. Differential centrifugation studies indicate that 50 to 80% of the crude homogenate's phospholipase D activity is membrane-bound. Density centrifugation experiments suggest that the membrane-bound phospholipase D activity is localized primarily on mitochondrial membranes. 相似文献
7.
Michael M. Shipley Jack W. Dillwith John R. Sauer Richard C. Essenberg Ralph W. Howard 《Archives of insect biochemistry and physiology》1993,23(1):37-52
Analysis of lipids in salivary glands of the lone star tick, Amblyomma americanum, demonstrated that arachidonic acid (20:4, n-6) comprises 8% of all fatty acids identified by gas chromatography. The occurrence of arachidonic acid and other C20 polyunsaturated fatty acids in tick salivary glands was confirmed by gas chromatography-mass spectrometry. Arachidonate is located entirely in the phospholipid fraction and is associated exclusively with phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Salivary glands stored and frozen for several months had a similar lipid composition as freshly dissected salivary glands, with the exception of a small amount of free arachidonic acid and an increase in lysophosphatidylcholine. Incubation of salivary gland homogenates with snake venom phospholipase A2 showed that most saturated fatty acids are esterified in the sn-1 position of PC and PE, with the unsaturated fatty acids in the sn-2 position. Approximately 75% of arachidonic acid is in the sn-2 position of PC and PE, adding support to the hypothesis that arachidonic acid is released into the cytoplasm after activation of a phospholipase A2 for subsequent metabolism to prostaglandins and/or other eicosanoids. © 1993 Wiley-Liss, Inc. 相似文献
8.
W.Thomas Shier 《Biochemical and biophysical research communications》1977,78(4):1168-1174
Exogenous lysolecithin inhibits prostaglandin E2 synthesis from arachidonic acid in bovine seminal vesicle microsomes at plausible physiological levels (lysolecithin-to-protein ratios ? 0.03 [w/w]) by inhibiting fatty acid cyclo-oxygenase activity. Structurally defined lysolecithins with varying fatty acid chain length exhibit varying effectiveness as inhibitors. Addition of equimolar quantities of free fatty acid lowers the lysolecithin concetration required for inhibition. Exogenous lysolecithin inhibits unstimulated and thrombin-stimulated prostaglandin E2 synthesis from endogenous substrate in SVBalb/3T3 cells. Serum treatment of SVBalb/3T3 cells, which generates endogenous lysolecithin and free fatty acids, decreases the efficiency of conversion of free arachidonic acid to prostaglandins. These results suggest a possible role for the products of phospholipase A2 action in the regulation of prostaglandin synthesis. 相似文献
9.
This study was undertaken to explore putative regulatory mechanisms involved in the inhibition of nuclear T3 binding (INB) by fatty acids. Ether extracts of intact rat liver nuclei contained INB-activity. Removement of the nuclear membrane resulted in the loss of INB-activity of the nuclei. Incubation of intact nuclei with phospholipase A2 increased nuclear INB-activity in a time- and dose-dependent manner; this was correlated with a rise of free fatty acid concentration in the ether extract. We conclude that fatty acids present in the nuclear membrane can be released by phospholipase A2, and are capable of inhibiting nuclear T3 binding. 相似文献
10.
Phospholipase A2 hydrolysis of membrane phospholipids causes structural alteration of the nicotinic acetylcholine receptor 总被引:1,自引:0,他引:1
M T Villar A Artigues J A Ferragut J M Gonzalez-Ros 《Biochimica et biophysica acta》1988,938(1):35-43
Thermal perturbation techniques have been used to probe structural alteration of the nicotinic acetylcholine receptor as a function of perturbations of its native membrane environment. Differential scanning calorimetry and a technique involving heat inactivation of the alpha-bungarotoxin-binding sites on the receptor protein reveal that there is a profound destabilization of the acetylcholine receptor structure when receptor-containing membranes are exposed to phospholipase A2. The characteristic calorimetric transition assigned to irreversible denaturation of the receptor protein and the heat inactivation profile of alpha-bungarotoxin-binding sites are shifted to lower temperatures by approx. 7 and 5 C degrees, respectively, upon exposure to phospholipase A2 at a phospholipase/neurotoxin binding site molar ratio of about 1:100. The effects of phospholipase A2 on receptor structure can be (i) reversed by using bovine serum albumin as a scavenger of phospholipase hydrolysis products of membrane phospholipids, and (ii) stimulated by incorporation into the membranes of free, polyunsaturated fatty acids. In particular, linolenic acid (18:3(n-3] causes detectable destabilization of the alpha-bungarotoxin binding sites on the receptor at free fatty acid/receptor molar ratios as low as 10:1. Furthermore, alteration of receptor structure by added phospholipase occurs very rapidly, which is consistent with the observation of rapid in situ phospholipase A2 hydrolysis of membrane phospholipids, particularly highly unsaturated phosphatidylethanolamine and phosphatidylserine. Based on previously published data on the inhibition of acetylcholine receptor cation-gating activity caused by the presence of either phospholipase A2 or free fatty acids (Andreasen T.J. and McNamee M.G. (1980) Biochemistry 19, 4719), we interpret our data as indicative of a correlation between structural and functional alterations of the membrane-bound acetylcholine receptor induced by phospholipase A2 hydrolysis products. 相似文献
11.
A procedure for the assay of free fatty acids which has been adapted for the assay of phospholipase A2 is described. This consists of the conversion of long chain fatty acids to fatty acyl-CoA using the Mg2(+)-dependent fatty acyl-CoA synthetase, [alpha-32P]ATP and coenzyme A. In order to ensure the complete conversion of the acid to its CoA ester pyrophosphatase is also added to the incubation mixture. AM32P formed in stoichiometric amounts is separated from the remaining AT32P by polyethyleneimine-cellulose thin-layer chromatography and the fatty acid content is calculated from the specific radioactivity of AT32P. As little as 1 to 3 nmol of fatty acids hydrolyzed from any phospholipid using nanogram amounts of phospholipase A2 can be estimated with reliability. The real advantage of the method is that it combines the sensitivity of a radiochemical procedure without having to use radiolabeled substrates for the assay of phospholipases. 相似文献
12.
Control of arachidonic acid accumulation in bone marrow-derived macrophages by acyltransferases 总被引:6,自引:0,他引:6
The turnover of phospholipid fatty acid moieties of bone marrow-derived macrophages was analyzed by separate determination of degrading and acylating activities. Acylating activities were followed in intact cells by incubation with excess arachidonic acid and degradation of phospholipids was followed in cells prelabeled with fatty acids. Significant phospholipase A2 activity was detectable only if the reutilization of liberated fatty acid was inhibited , e.g. by p-chloromercuribenzoate. It was of interest that the divalent cation ionophore A 23187 and various antiphlogistic drugs like indomethacin, diclofenac, and acetylsalicylic acid were found to inhibit the acylation reaction. These compounds led to increased levels of free arachidonic acid in stimulated, as well as in unstimulated cells. Increased activities of phospholipase A2 were achieved by treatment with the bivalent cation ionophore A 23187 and with zymosan. The effect of zymosan obtained from various sources was found to be exclusively due to contamination of tee zymosan particles with phospholipase A2 activity. Even when the cellular phospholipase activity was increased by the addition of exogenous phospholipase activity contained in the zymosan particles, degradation of cellular phospholipids was not measurable unless the reacylation was inhibited. These results suggest that in the cells studied, the level of free arachidonic acid is mainly controlled by the activity of the lysophosphatide acyltransferase. 相似文献
13.
Effect of unsaturated fatty acids and Ca2+ on phosphatidylinositol synthesis and breakdown 总被引:1,自引:0,他引:1
CDP-diglyceride : inositol transferase was inhibited by unsaturated fatty acids. The inhibitory activity decreased in the following order: arachidonic acid greater than linolenic acid greater than linoleic acid greater than oleic acid greater than or equal to palmitoleic acid. Saturated fatty acids such as myristic acid, palmitic acid, and stearic acid had no effect. Calcium ion also inhibited the activity of CDP-diglyceride : inositol transferase. In rat hepatocytes, arachidonic acid inhibited 32P incorporation into phosphatidylinositol and phosphatidic acid without any significant effect on 32P incorporation into phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Ca2+ ionophore A23187 also inhibited 32P incorporation into phosphatidylinositol. However, 32P incorporation into phosphatidic acid was stimulated with Ca2+ ionophore A23187. Phosphatidylinositol-specific phospholipase C was activated by unsaturated fatty acids. Polyunsaturated fatty acids such as arachidonic acid and linolenic acid had a stronger effect than di- and monounsaturated fatty acids. Saturated fatty acids had no effect on the phospholipase C activity. The phospholipase C required Ca2+ for activity. Arachidonic acid and Ca2+ had synergistic effects. These results suggest the reciprocal regulation of phosphatidylinositol synthesis and breakdown by unsaturated fatty acids and Ca2+. 相似文献
14.
Phospholipase activity in bacteriophage-infected Escherichia. II. Activation of phospholipase by T4 ghost infection. 总被引:1,自引:0,他引:1
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C S Buller 《Journal of virology》1975,15(5):1141-1147
The release of free fatty acids from the phospholipids of Escherichia coli is initiated immediately after the attachment of T4 ghosts. A similar accumulation of free fatty acids is observed if the cells are infected with T4 phage in the presence of chloramphenicol or puromycin. An early accumulation of free fatty acids, however, is not observed in T4 infections in which chloramphenicol or puromycin are not present, nor does it occur if the E. coli are infected with T4 phage before ghost infection, suggesting that phage products can prevent the phospholipid deacylation. If E. coli is infected with T4 ghosts before T4 phage infection, the accumulation of free fatty acids is not suppressed. When phospholipase-deficient E, coli are infected with T4 ghosts the appearance of free fatty acids is not observed, suggesting that T4 ghost attachment can activate the phospholipase of wild-type E. coli. Although the formation of free fatty acid apparently is a consequence of activation of the detergent-resistant phospholipase of the outer membrane, it is not observed in mutants deficient in the detergent-sensitive phospholipase. 相似文献
15.
Coupling Among Energy Failure, Loss of Ion Homeostasis, and Phospholipase A2 and C Activation During Ischemia 总被引:1,自引:1,他引:0
Ken-ichiro Katsura‡ Elena B. Rodriguez de Turco† Jaroslava Folbergrov᧠Nicolas G. Bazan† Bo K. Siesjö 《Journal of neurochemistry》1993,61(5):1677-1684
Abstract— The objective of the present experiments was to correlate changes in cellular energy metabolism, dissipative ion fluxes, and lipolysis during the first 90 s of ischemia and, hence, to establish whether phospholipase A2 or phospholipase C is responsible for the early accumulation of phospholipid hydrolysis products. Ischemia was induced for 15–90 s in rats, extracellular K+ (K+ e ) was recorded, and neocortex was frozen in situ for measurements of labile tissue metabolites, free fatty acids, and diacylglycerides. Ischemia of 15-and 30-s duration gave rise to a decrease in phosphocreatine concentration and a decline in the ATP/free ADP ratio. Although these changes were accompanied by an activation of K+ conductances, there were no changes in free fatty acids until after 60s, when free arachidonic acid accumulated. An increase in other free fatty acids and in total diacylglyceride content did not occur until after anoxic depolarization. The results demonstrate that the early functional changes, such as activation of K+ conductances, are unrelated to changes in lipids or lipid mediators. They furthermore suggest that the initial lipolysis occurs via both phospholipase A2 and phospholipase C, which are activated when membrane depolarization leads to influx of calcium into cells. 相似文献
16.
Signal-activated phospholipase A2 cleavesphosphatidylcholine (PC) into free fatty acids and LPC, respectively.Using bis-BODIPY-PC as an indicator substrate for phospholipaseA2 which is taken up by parsley cells, active auxins atconcentrations as low as 1 M and a fungal elicitor induced fattyacid-accumulation. Nordihydroguajaretic acid inhibited the accumulationof fatty acid induced by the elicitor. In addition to this, theelicitor, but not auxin, decreased the pool size of diacylglycerol,which seemed to originate from a PC-splitting phospholipase C, whichwould be a new enzyme in plant signal transduction. However, thiselicitor is known to rapidly increase cytosolic calcium in parsley cellsand this activates phospholipase C. Thus, activation of phospholipase Cshould lead to an increase of diacylglycerol and not to a decrease whichmight indicate a discrepancy between animal and plant phospholipidsignal transduction. 相似文献
17.
Michael Gjedde Palmgren Marianne Sommarin Peter Ulvlskov Peter Leth Jørgensen 《Physiologia plantarum》1988,74(1):11-19
Plasma membrane vesicles were purified from 8-day-old oat ( Avena sativa L. cv. Brighton) roots in an aqueous polymer two-phase system. The plasma membranes possessed high specific ATPase activity [ca 4 μmol P1 (mg protein)−1 min−1 at 37°C]. Addition of lysophosphatidylcholine (lyso-PC) produced a 2–3 fold activation of the plasma membrane ATPase, an effect due both to exposure of latent ATP binding sites and to a true activation of the enzyme. Lipid activation increased the affinity for ATP and caused a shift of the pH optimum of the H+ -ATPase activity to 6.75 as compared to pH 6.45 for the negative H+ -ATPase. Activation was dependent on the chain length of the acyl group of the lyso-PC, with maximal activition obtained by palmitoyl lyso-PC. Free fatty acids also activated the membrane-bound H+ -ATPase. This activation was also dependent on chain length and to the degree of unsaturation, with linolenic and arachidonic acid as the most efficient fatty acids. Exogenously added PC was hydrolyzed to lyso-PC and free fatty acids by an enzyme in the plasma membrane preparation, presumably of the phospholipase A type. Both lyso-PC and free fatty acids are products of phospholipase A2 (EC 3.1.1.4) action, and addition of phospholipase A2 from animal sources increased the H+ -ATPase activity within seconds. Interaction with lipids and fatty acids could thus be part of the regulatory system for H+ -ATPase activity in vivo, and the endogenous phospholipase may be involved in the regulation of the H+ -ATPase activity in the plasma membranne. 相似文献
18.
cis- and trans-unsaturated fatty acids with 18 carbon atoms (oleic, linoleic, elaidic and linolelaidic acid) inhibited aggregation of washed rabbit platelets stimulated with collagen, arachidonic acid and U46619 when in the same concentration ranges. Thrombin-induced aggregation was not affected by any of them. Saturated fatty acid (stearic acid) had no effect on this response. The inhibition is independent of the induced change in membrane fluidity, since trans-isomers could not induce the change in fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. Unsaturated fatty acids, except linoleic acid, did not interfere with the formation of thromboxane B2 from exogenously added arachidonic acid. All the unsaturated fatty acids only slightly inhibited the arachidonic acid liberation by phospholipase A2 in platelet lysate. This indicates that the unsaturated fatty acids may block a process after formation of thromboxane A2 in response to collagen and arachidonic acid. The increase in phosphatidic acid formation stimulated with U46619 was inhibited dose dependently by each of the unsaturated fatty acids but that stimulated with thrombin was not affected by any of them. Phospholipase C activity measured by diacylglycerol formation in unstimulated platelet lysate was not inhibited by the fatty acids. The elevation of cytosolic free Ca2+ induced by arachidonic acid or U46619 and Ca2+ influx by collagen were inhibited almost completely at the same concentration as that which inhibited their aggregation. These data suggest that the unsaturated fatty acids were intercalated into the membrane and inhibited collagen- and arachidonic acid-induced platelet aggregation by causing a significant suppression of the thromboxane A2-mediated increase in cytosolic free Ca2+, probably due to interference with the receptor-operated Ca2+ channel. 相似文献
19.
Mechanism of Arachidonic Acid Liberation During Ischemia in Gerbil Cerebral Cortex 总被引:20,自引:15,他引:5
Koji Abe Kyuya Kogure Hirotaka Yamamoto Masaoki Imazawa Kenji Miyamoto 《Journal of neurochemistry》1987,48(2):503-509
Once brain ischemia was induced in the gerbil cerebral fronto-parietal cortex, serial changes occurred in energy metabolites and various lipids. The amounts of inositol-containing phospholipids began to decrease immediately after energy failure, followed by an increase in the amount of 1,2-diacylglycerol with a subsequent liberation of arachidonic acid and other free fatty acids. The fatty acid compositions of inositol-containing phospholipids, of 1,2-diacylglycerols produced by ischemia, and of free fatty acids liberated during ischemia were quite similar. The amount of stearic acid liberated was much larger than that of arachidonic acid between 30 s and 1 min of ischemia. On the other hand, there was no significant decrease in the amount of the other phospholipids except for phosphatidic acid. Furthermore, there was also no change in the fatty acid composition of phosphatidylcholine or phosphatidylethanolamine throughout 15 min of ischemia. The amount of cytidine-monophosphate reached a peak (36.7 nmol/g wet wt) at 2 min of ischemia. These results indicated that arachidonic acid was predominantly liberated from inositol-containing phospholipids by phospholipase C, and by the diglyceride lipase and monoglyceride lipase system rather than from phosphatidylcholine or phosphatidylethanolamine by phospholipase A2 or plasmalogenase or choline phosphotransferase during the early period of ischemia. 相似文献
20.
This study characterizes free fatty acid release in a neuroblastoma cell line (Neuro-2A), a potential model system for the study of factors that control phospholipase A2 in neurons. Two compounds, bicuculline (an antagonist at -aminobutyric acid receptors), and A23187 (a Ca2+ ionophore), were examined. The release of endogenous fatty acids and the turnover of radiolabeled arachidonic and docosahexaenoic acids were measured. The cells actively incorporated radiolabeled fatty acids into various glycerolipid pools. Both endogenous fatty acids and radiolabeled fatty acids were released from glycerolipids in a time-dependent manner. Phosphatidylcholine was a major source of released fatty acids. Release of free fatty acids was markedly stimulated by both bicuculline and A23187. We conclude that the Neuro-2A cell contain phospholipase activity that is sensitive to Ca2+ ionophore and bicuculline, and may provide a good system for further studies on the regulation of phospholipase A2 in neurons.Abbteviations 160
palmitic acid
- 180
stearic acid
- 181
oleic acid
- 182
linoleic acid
- 183
linolenic acid
- 204
arachidonic acid
- 226
docosahexaenoic acid
- DG
diacylglycerol
- FAME
fatty acid methyl ester
- FFA
free fatty acid
- GABA
-aminobutyric acid
- PA
phosphatidic acid
- PC
phosphatidylcholine
- PE
phosphatidylethanolamine
- PI
phosphatidylinositol
- PS
phosphatidylserine
- TG
triacylglycerol 相似文献