scholarly journals Biosynthesis of platelet-activating factor in glandular gastric mucosa. Evidence for the involvement of the ‘de novo’ pathway and modulation by fatty acids

1988 ◽  
Vol 254 (3) ◽  
pp. 707-714 ◽  
Author(s):  
S Fernandez-Gallardo ◽  
M A Gijon ◽  
M C Garcia ◽  
E Cano ◽  
M Sanchez Crespo
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Gastric Mucosa ◽  
De Novo ◽  
Potent Inhibitor ◽  
Specific Activity ◽  
Platelet Activating Factor ◽  
Exocrine Glands ◽  
Acetyl Coa ◽  
Dose Dependent

The biosynthesis of platelet-activating factor (PAF), a phospholipid autocoid with potent ulcerogenic properties that is produced in secretory exocrine glands by physiological secretagogues, was assessed in microsomal preparations of glandular gastric mucosa. For this purpose, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PAF):acetyl-CoA acetyltransferase (EC 2.3.1.67); the enzymes of the ‘de novo’ pathway: 1-O-alkyl-2-lyso-sn-glycero-3-phosphate (alkyl-lyso-GP):acetyl-CoA acetyltransferase and 1-O-alkyl-2-acetyl-sn-glycerol (alkylacetyl-G):CDP-choline cholinephosphotransferase (EC 2.7.8.16); and some enzymes involved in the catabolism of PAF and lyso-PAF were assayed. Only the enzymes of the ‘de novo’ pathway and small amounts of PAF acetylhydrolase, phospholipase A2 and a lysophospholipase D acting on either lipids could be detected in the gastric preparations, whereas lyso-PAF:acetyl-CoA acetyltransferase activity was undetectable. The specific activity of alkyl-lyso-GP:acetyl-CoA acetyltransferase in the gastric mucosa was about one-tenth of that found in spleen microsomes and its apparent Km for acetyl-CoA was 454 microM compared with 277 microM in spleen microsomes. Glandular mucosa homogenates contained preformed PAF at a concentration of 2.7 +/- 0.7 ng equivalents of PAF (hexadecyl)/mg of protein. When gastric microsomes were incubated with micromolar concentrations of fatty acids (arachidonic, palmitic and oleic) prior to the assay of dithiothreitol (DTT)-insensitive cholinephosphotransferase, a dose-dependent reduction in the formation of PAF was observed, arachidonic acid being the most potent inhibitor, followed by linoleic acid (only tested on spleen microsomes) and oleic acid. By contrast, 1,2-diolein and phosphatidylcholine (dipalmitoyl) showed no or little effect. These results indicate that glandular gastric mucosa can produce PAF through the ‘de novo’ pathway, and that fatty acids, especially unsaturated, can reduce that synthesis by modulating the expression of DTT-insensitive cholinephosphotransferase.

scholarly journals Biosynthesis of platelet-activating factor (PAF) in human polymorphonuclear leucocytes. The role of lyso-PAF disposal and free arachidonic acid

1990 ◽  
Vol 268 (1) ◽  
pp. 91-98 ◽  
Author(s):  
M D C Garcia ◽  
S Fernandez-Gallardo ◽  
M A Gijon ◽  
C Garcia ◽  
M L Nieto ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Eicosatetraenoic Acid ◽  
Polymorphonuclear Leucocytes ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Dose Dependent

Theophylline and 1-methyl-3-isobutylxanthine (MIX), compounds that block eicosanoid formation and modulate phospholipase A2 activity, inhibited in a dose-dependent manner the formation of both leukotriene B4 (LTB4) and platelet-activating factor (PAF) by human polymorphonuclear leucocytes (PMN) in response to ionophore A23187. Theophylline and MIX lacked any inhibitory effect on acetyl-CoA: lyso-PAF acetyltransferase activity, which is the rate-limiting step for PAF biosynthesis in PMN. The effect of theophylline and MIX on PAF formation could be reversed by incubating the cells in the presence of 1-10 microM exogenous lyso-PAF. Incubation of PMN homogenates in the presence of unsaturated non-esterified fatty acids resulted in dose-dependent inhibition of the acetyltransferase. This effect was linked to the presence of a free carboxyl group, since both arachidonic acid methyl ester and palmitoyl-arachidonoyl phosphatidylcholine lacked inhibitory activity. This inhibitory effect was also dependent on the number of double bonds, since arachidonic acid (C20:4) and eicosapentaenoic acid (C20:5) displayed maximal effect. Kinetic analysis showed that the effect of arachidonic acid was consistent with competitive inhibition, with a Ki value of about 19 microM. Oxidative metabolites of arachidonic acid showed a lesser inhibitory effect with the following order of potency: arachidonic acid greater than 15-HETE (15-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than LTB4 greater than 5-HETE (5-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than lipoxin A4. Examination of enzymes involved in CoA-dependent acylation revealed a low activity of both arachidonoyl-CoA synthetase and arachidonoyl-CoA: lyso-PAF arachidonoyltransferase. These data indicate a strong influence on PAF biosynthesis of the products of the phospholipase A2 reaction, with lyso-PAF disposal being a critical event for PAF formation, and unsaturated fatty acids acting as feed-back inhibitors. The conversion of arachidonic acid via oxidative metabolism into less active inhibitors of acetyl-CoA:lyso-PAF acetyltransferase seems to be an additional mechanism of modulation of this enzyme activity, linked to the function of lipoxygenases. Finally, the enzyme activities involved in arachidonoyl-CoA-dependent acylation of lyso-PAF show a low efficiency in capturing arachidonic acid.

scholarly journals Adrenaline Stimulation of Phospholipid Metabolism in Adipocyte Ghosts

1987 ◽  
Vol 40 (4) ◽  
pp. 405
Author(s):  
David Mann ◽  
Audrey M Bersten
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Adenylate Cyclase ◽  
Phospholipid Metabolism ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Membrane Phospholipids ◽  
Dose Dependent ◽  
Stimulation Of

The incorporation of long-chain fatty acids into phospholipids has been detected in adipocyte ghosts that were incubated with [1_14 C] stearic, [1_14 C] linoleic or [l_14C] arachidonic acid. Adrenaline and adenosine activated this incorporation within 15 s of exposure of the ghosts to the hormones and the response was dose dependent. Maximum incorporation of labelled linoleic acid occurred at 10-5 M adrenaline and 10-7 M adenosine. The a-agonist phenylephrine and the ~-agonist isoproterenol were also shown to stimulate the incorporation of fatty acid in a dose dependent manner. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were each labelled preferentially with linoleic or arachidonic acid. p-Bromophenacylbromide, quinacrine and centrophenoxine inhibited the adrenaline-stimulated incorporation of fatty acids into ghost membrane phospholipids, and p-bromophenacylbromide also reduced the activation of adenylate cyclase by adrenaline. NaF, an activator of adenylate cyclase, like adrenaline, stimulated the incorporation of linoleic acid into ghost membrane phospholipids.

Effect of Thiolactomycin on de novo Fatty Acid Biosynthesis in Plants

1990 ◽  
Vol 45 (5) ◽  
pp. 518-520 ◽  
Author(s):  
Manfred Focke ◽  
Andrea Feld ◽  
Hartmut K. Lichtenthaler
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Fatty Acid Synthetase ◽  
Acetate Incorporation ◽  
Acid Biosynthesis ◽  
Acetyl Coa ◽  
Malonyl Coa ◽  
Total Fatty Acids

Thiolactomycin was shown to be a potent inhibitor of de novo fatty acid biosynthesis in intact isolated chloroplasts (measured as [14C]acetate incorporation into total fatty acids). In our attempt to further localize the inhibition site we confirmed the inhibition with a fatty acid synthetase preparation, measuring the incorporation of [14C]malonyl-CoA into total fatty acids. From the two proposed enzymic targets of the fatty acid synthetase by thiolactomycin we could exclude the acetyl-CoA: ACP transacetylase. It appears that the inhibition by thiolactomycin occurs on the level of the condensing enzymes, i.e. the 3-oxoacyl-ACP synthases. We also demonstrated that the two starting enzymes of de novo fatty acid biosynthesis, the acetyl-CoA synthetase and the acetyl-CoA carboxylase, are not affected by thiolactomycin.

scholarly journals Fatty Acid-mediated Gastroprotection Does Not Correlate with Prostaglandin Elevation in Rats Exposed to Various Chemical Insults

1994 ◽  
Vol 31 (6) ◽  
pp. 679-688 ◽  
Author(s):  
K. G. Mandel ◽  
T. A. Bertram ◽  
M. K. Eichhold ◽  
S. C. Pepple ◽  
M. J. Doyle
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Oleic Acid ◽  
Fatty Acid ◽  
Gastric Mucosa ◽  
Linolenic Acid ◽  
Mucosal Damage ◽  
Taurocholic Acid ◽  
Gastric Mucosal Damage ◽  
Gastric Mucosal Lesions

This study involved a comparison of activity of several long-chain fatty acids (arachidonic acid, dihomo-[γ]-linolenic acid, linoleic acid, and oleic acid) for protection against gastric mucosal damage elicited by taurocholic acid, acidified aspirin, and ethanol in rats. Each damaging agent induced gastric mucosal lesions in the corpus. Mucosal damage was induced by all agents, and all fatty acids protected the gastric mucosa; however, ethanol and arachidonic acid were the most potent damaging and protecting agents, respectively. Maximally protective doses for prevention of taurocholic acid-induced damage by arachidonic, dihomo-[γ]-linolenic, linoleic, and oleic acids were 50, 200, 100, and 200 mg/kg, respectively; however, 10 mg/kg arachidonic acid reduced lesion length by >50%, whereas minimally effective doses of the other fatty acids were ≥50 mg/kg. Similar potency differences were observed for fatty acid protection against acidified aspirin-induced gastric damage. Although all the fatty acids reduced macroscopic damage, histologic studies showed they did not totally eliminate surface mucosal damage. Microscopic analysis showed that treatment with dihomo-[γ]-linolenic acid or oleic acid attenuated depletion of neutral and acidic glycoproteins from the mucus neck cells of the gastric mucosa in response to exposure to taurocholic acid. Despite having similar gastroprotective activity, arachidonic, dihomo-[γ]-linolenic, linoleic, and oleic acids had very dissimilar abilities to elevate gastric mucosal E-series prostaglandins. Both arachidonic and dihomo-[γ]-linolenic acids elevated E-series prostaglandins, but arachidonic acid had 2–5-fold greater gastroprotective potency. Furthermore, oleic and linoleic acids, which had protective potency similar to that dihomo-[γ]-linolenic acid, did not significantly elevate prostaglandins. These studies failed to demonstrate an absolute correlation between prostaglandin elevation and gastroprotection. The results of this investigation suggest that prostaglandin elevation, although associated with gastroprotection, does not appear to be the sole mechanism for fatty acid-mediated protection of rat gastric mucosa.

Inhibition of the synthesis of glycosphingolipid by a ceramide analogue (PPMP) in the gastrulation of Bufo arenarum

Zygote ◽  
2000 ◽  
Vol 8 (2) ◽  
pp. 159-169 ◽  
Author(s):  
Manuel J. Aybar ◽  
Analía Fuentes ◽  
Sara S. Sánchez
Keyword(s):  
Morphological Analysis ◽  
De Novo ◽  
Potent Inhibitor ◽  
Developmental Rate ◽  
Dependent Manner ◽  
Blastula Stage ◽  
Mesodermal Cell ◽  
Bufo Arenarum ◽  
Dose Dependent

In the present study the role of glycosphingolipids (GSL) in amphibian development was investigated. We analysed the de novo synthesis of neutral GSL and gangliosides through the initial stages of Bufo arenarum embryo development and their participation during gastrulation using 1-phenyl-2-palmitoyl-3-morpholino-1-propanol (PPMP), a potent inhibitor of glucosylceramide synthase. Ganglioside synthesis began at the blastula stage and reached a maximum during gastrulation (stages 10-12) while neutral GSL synthesis showed a slight gradual increase, the former being quantitatively more significant than the latter. Ganglioside synthesis was reduced by 90% while neutral GSL synthesis was inhibited by 65% when embryos at blastula stage were cultured for 24 h in 20 μM PPMP. The depletion of GSL from amphibian embryos induced an abnormal gastrulation in a dose-dependent manner. We found that PPMP had a pronounced effect on development since no embryos exhibited normal gastrulation; their developmental rate either slowed down or, more often, became totally arrested. Morphological analysis of arrested embryos revealed inhibition of the gastrulation morphogenetic movements. Analysis of mesodermal cell morphology in those embryos showed a severe decrease in the number and complexity of cellular extensions such as filopodia and lamellipodia. Mesodermal cells isolated from PPMP-treated embryos had very low adhesion percentages. Our results suggest that glycosphingolipids participate in Bufo arenarum gastrulation, probably through their involvement in cell adhesion events.

scholarly journals Transfer of glucose hydrogens via acetyl-CoA, malonyl-CoA, and NADPH to fatty acids during de novo lipogenesis

2019 ◽  
Vol 60 (12) ◽  
pp. 2050-2056 ◽  
Author(s):  
Getachew Debas Belew ◽  
Joao Silva ◽  
Joao Rito ◽  
Ludgero Tavares ◽  
Ivan Viegas ◽  
...  
Keyword(s):  
Fatty Acids ◽  
De Novo ◽  
De Novo Lipogenesis ◽  
Acetyl Coa ◽  
Malonyl Coa

scholarly journals Lack of mitochondria-generated acetyl-CoA by pyruvate dehydrogenase complex downregulates gene expression in the hepatic de novo lipogenic pathway

2016 ◽  
Vol 311 (1) ◽  
pp. E117-E127 ◽  
Author(s):  
Saleh Mahmood ◽  
Barbara Birkaya ◽  
Todd C. Rideout ◽  
Mulchand S. Patel
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Pyruvate Dehydrogenase ◽  
De Novo ◽  
Pyruvate Dehydrogenase Complex ◽  
Acid Oxidation ◽  
Acetyl Coa ◽  
Key Genes ◽  
Dehydrogenase Complex

During the absorptive state, the liver stores excess glucose as glycogen and synthesizes fatty acids for triglyceride synthesis for export as very low density lipoproteins. For de novo synthesis of fatty acids from glucose, the mitochondrial pyruvate dehydrogenase complex (PDC) is the gatekeeper for the generation of acetyl-CoA from glucose-derived pyruvate. Here, we tested the hypothesis that limiting the supply of PDC-generated acetyl-CoA from glucose would have an impact on expression of key genes in the lipogenic pathway. In the present study, although the postnatal growth of liver-specific PDC-deficient (L-PDCKO) male mice was largely unaltered, the mice developed hyperinsulinemia with lower blood glucose levels in the fed state. Serum and liver lipid triglyceride and cholesterol levels remained unaltered in L-PDCKO mice. Expression of several key genes ( ACL, ACC1) in the lipogenic pathway and their upstream regulators ( LXR, SREBP1, ChREBP) as well as several genes in glucose metabolism ( Pklr, G6pd2, Pck1) and fatty acid oxidation ( FAT, Cpt1a) was downregulated in livers from L-PDCKO mice. Interestingly, there was concomitant upregulation of lipogenic genes in adipose tissue from L-PDCKO mice. Although, the total hepatic acetyl-CoA content remained unaltered in L-PDCKO mice, modified acetylation profiles of proteins in the nuclear compartment suggested an important role for PDC-generated acetyl-CoA in gene expression in de novo fatty acid synthesis in the liver. This finding has important implications for the regulation of hepatic lipid synthesis in pathological states.

Relationship of primer specificity of fatty acid de novo synthetase to fatty acid composition in 10 species of bacteria and yeasts

1980 ◽  
Vol 26 (8) ◽  
pp. 893-898 ◽  
Author(s):  
Toshi Kaneda ◽  
E. J. Smith
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Chain Length ◽  
De Novo ◽  
Micrococcus Luteus ◽  
Straight Chain ◽  
Acetyl Coa ◽  
Branched Chain Fatty Acids ◽  
Branched Chain ◽  
Chain Fatty Acids

Fatty acid compositions of lipids from six bacteria and four yeasts were determined. Fatty acid de novo synthetases were investigated with respect to chain length specificity towards acyl-CoA primers of various chain lengths.Four species of bacteria (Bacillus subtilis, Corynebacterium cyclohexanicum, Micrococcus luteus, and Pseudomonas maltophilia) possess branched-chain fatty acids of the iso and anteiso series as the major acids. De novo synthetases from these organisms exhibited specificity towards the chain length of the primer in the order butyrl-CoA > propionyl-CoA [Formula: see text] acetyl-CoA. The remainder, two bacteria and all four yeasts, have the straight-chain type of fatty acids only and fall into two groups: (1) Eschericia coli B, Pseudomonas fluorescens, and Saccharomyces cerevisiae, which utilize the primers in the order acetyl-CoA > propionyl-CoA [Formula: see text] butyryl-CoA; and (2) Candida sake, Candida tropicalis, and Rhodolorula glutinis, which show the order propionyl-CoA > acetyl-CoA [Formula: see text] butyryl-CoA.L-α-Keto-β-methylvalerate, a precursor of the branched-chain primers, can be used as a source of primer for fatty acid synthesis by the organisms with branched-chain acids but not by those with the straight-chain type.The results indicate that organisms having straight-chain fatty acids lack the branched-chain equivalents for two reasons: first, their enzymes are not active toward primers with more than three carbons, and second, they lack a system of supplying suitable branched-chain primers.It appears that activities of de novo synthetases from the organisms having straight-chain fatty acids generally have much higher activities than those from the organisms possessing branched-chain fatty acids.

Notes: Inhibition of the Acetyl-CoA Carboxylase of Barley Chloroplasts by Cycloxydim and Sethoxydim

1987 ◽  
Vol 42 (11-12) ◽  
pp. 1361-1363 ◽  
Author(s):  
Manfred Focke ◽  
Hartmut K. Lichtenthaler
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Enzyme Preparation ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Acetyl Coa Carboxylase ◽  
Acid Biosynthesis ◽  
Hordeum Vulgare L ◽  
Acetyl Coa ◽  
Malonyl Coa

The effect of the three cyclohexane-1,3-dione derivatives cycloxydim, sethoxydim and clethodim on the incorpora­tion of 14C-labelled acetate, malonate. acctyl-CoA or malonyl-CoA into fatty acids was studied in an enzyme preparation isolated from barley chloroplasts (Hordeum vulgare L. var. “Alexis”). The herbicides cycloxydim, clethodim and sethoxydim block the de novo fatty acid biosynthesis from [2-14C]acetatc and [1-14C]acetyl-CoA, whereas that of [2-14C]malonatc and [2-14C)malonyl-CoA is not affected. The data indicate that the mode of action of the cyclohexane-1,3-dione derivatives in the sensitive bar­ley plant consists in the inhibition of de novo fatty acid biosynthesis by blocking the acetyl-CoA carboxylase (EC 6.4.1.2.).

scholarly journals The BADC and BCCP subunits of chloroplast acetyl-CoA carboxylase sense the pH changes of the light–dark cycle

2020 ◽  
Vol 295 (29) ◽  
pp. 9901-9916 ◽  
Author(s):  
Yajin Ye ◽  
Yan G. Fulcher ◽  
David J. Sliman ◽  
Mizani T. Day ◽  
Mark J. Schroeder ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Light Adaptation ◽  
De Novo ◽  
Intrinsic Disorder ◽  
Ph Effects ◽  
Acetyl Coa Carboxylase ◽  
Dark Cycle ◽  
Acetyl Coa ◽  
Ph Changes ◽  
Mutant Lines

Acetyl-CoA carboxylase (ACCase) catalyzes the first committed step in the de novo synthesis of fatty acids. The multisubunit ACCase in the chloroplast is activated by a shift to pH 8 upon light adaptation and is inhibited by a shift to pH 7 upon dark adaptation. Here, titrations with the purified ACCase biotin attachment domain-containing (BADC) and biotin carboxyl carrier protein (BCCP) subunits from Arabidopsis indicated that they can competently and independently bind biotin carboxylase (BC) but differ in responses to pH changes representing those in the plastid stroma during light or dark conditions. At pH 7 in phosphate buffer, BADC1 and BADC2 gain an advantage over BCCP1 and BCCP2 in affinity for BC. At pH 8 in KCl solution, however, BCCP1 and BCCP2 had more than 10-fold higher affinity for BC than did BADC1. The pH-modulated shifts in BC preferences for BCCP and BADC partners suggest they contribute to light-dependent regulation of heteromeric ACCase. Using NMR spectroscopy, we found evidence for increased intrinsic disorder of the BADC and BCCP subunits at pH 7. We propose that this intrinsic disorder potentially promotes fast association with BC through a “fly-casting mechanism.” We hypothesize that the pH effects on the BADC and BCCP subunits attenuate ACCase activity by night and enhance it by day. Consistent with this hypothesis, Arabidopsis badc1 badc3 mutant lines grown in a light–dark cycle synthesized more fatty acids in their seeds. In summary, our findings provide evidence that the BADC and BCCP subunits function as pH sensors required for light-dependent switching of heteromeric ACCase activity.

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