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1.
The differences in distribution of geometric isomers of unsaturated PC hydroperoxides generated by free radical oxidation
were compared, as corresponding hydroxy analogs, in heterogeneous liposomes and in a homogeneous methanol solution by using
HPLC with UV detection due to the presence of conjugated dienes. Identification of fractionated peak components was carried
out by GC-MS. When the oxidation of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine, PC(16∶0/18∶2), was initiated in liposomes by a hydrophilic azo radical initiator, and in a methanol
solution by a hydrophobic azo radical initiator, there was no significant difference in the relative percentages of 1-palmitoyl-2-(9-hydroxy-trans-10,trans-12-octadecadienoyl)-sn-glycero-3-phosphocholine (9-t,t-OH PC) and 1-palmitoyl-2-(13-hydroxy-trans-9,trans-11-octadecadienoyl)-sn-glycero-3-phosphocholine (13-t,t-OH PC) between the PC oxidized in liposomes and in the methanol solution. For the oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, PC(16∶0/20∶4), the relative percentage of 1-palmitoyl-2-(5-hydroxy-trans-6,cis-8,11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (5-OH PC) was significantly higher (P<0.01) than that of 1-palmitoyl-2-(15-hydroxy-cis-5,8,11,trans-13-eicosatetraenoyl)-sn-glycero-3-phosphocholine (15-OH PC) in liposomes. For the homogeneous methanol solution of PC(16∶0/20∶4), the relative percentage
of 5-OH PC was close to that of 15-OH PC. For the PC(16∶0/20∶4) oxidized in bulk with added pentamethylchromanol, the individual
amount of 15-OH PC, 1-palmitoyl-2-(11-hydroxy-cis-5,8trans-12,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (11-OH PC), 1-palmitoyl-2-(12-hydroxy-cis-5,8,trans-10,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (12-OH PC), 1-palmitoyl-2-(8-hydroxy-cis-5,trans-9,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (8-OH PC), 1-palmitoyl-2-(9-hydroxy-cis-5,trans-7,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (9-OH PC), and 5-OH PC were close to each other compared to the corresponding values in liposomes
and in methanol solution. The results obtained by gel permeation chromatography of the PC liposomes containing hydrophilic
2,2′-azobis-2-amidinopropane) dihydrochloride (AAPH) suggest that the AAPH added to the liposomes of PC(16∶0/20∶4) was partitioned
into the water phase and out of the hydrophobic region of the fatty acyl moieties of the PC. These results confirm that the
distance that exists in the bis-allylic carbons of the unsaturated fatty acyl moieties of PC from the interface between the
hydrophilic region of PC and the water phases played an important role in influencing hydrogen abstraction to form a symmetrical
distribution of hydroperoxide isomers in both the heterogeneous liposomes and the homogeneous methanol solution. 相似文献
2.
Jen-sie Tou 《Lipids》1987,22(5):333-337
The present study showed that platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, PAF), but not lysoPAF (1-O-hexadecyl-sn-glycero-3-phosphocholine) rapidly (within 15 sec) stimulated the incorporation of both [1-14C]arachidonate and [1-14C]docosahexaenoate into phosphatidylinositol (PI) and phosphatidylcholine (PC) in human neutrophils. Concomitantly, it inhibited
the formation of labeled phosphatidic acid from both fatty acids. The magnitude of stimulation (percentage of control) was
greater in PI than in PC for the incorporation of arachidonate and vice versa for the incorporation of docosahexaenoate. It
reached a maximum at 10−7 M and started to decline at 10−6 M. Extracellular Ca2+ was not essential for the action of PAF on phospholipid acylation. The distribution of labeled arachidonate in the molecular
species of PC was not altered by PAF after 1 min incubation, suggesting that the increased formation of arachidonyl-PC during
the early stage of neutrophil-PAF interaction was not originated from the added PAF. No measurable changes in the mass of
each phospholipid were detected in neutrophils challenged by PAF from 15 sec to 2 min. The data suggest that the increased
incorporated of extracellular fatty acids into PI and PC elicited by PAF may be secondary to increased deacylation of these
phospholipids, and the magnitude of stimulation reflects the specificity of acyltransferase catalyzing the acylation of lysoPI
and lysoPC by fatty acyl-CoA. 相似文献
3.
Resolution of individual molecular species of human platelet 1,2-diradyl-sn-glycero-3-phosphocholines and 1,2-diradyl-sn-glycero-3-phosphoethanolamines by reverse phase high pressure liquid chromatography (HPLC) allowed a thorough analysis of
those phospholipids labeled with [3H]arachidonic acid. Approximately 54% and 16% of the total incorporated radiolabel was found in choline glycerophospholipids
and ethanolamine glycerophospholipids, respectively, with ca. 90% of this being found in the 1,2-diacyl molecular species.
Eighty percent of [3H]-arachidonic acid incorporated into 1-acyl-2-arachidonoyl-sn-glycero-3-phosphocholine in resting platelets was equally distributed between 1-palmitoyl-2-arachidonoyl and 2-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, while 70% of the radiolabel in 1-acyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine was found in 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine. Thrombin stimulation (5 U/ml for 5 min) resulted in deacylation of all 1-acyl-2-[3H]arachidonoyl molecular species of 1-acyl-2-arachidonoyl-sn-glycero-3-phosphocholine and 1-acyl-2-arachidonoyl-sn-glycero-3-ethanolamine. There was also a slight increase in 1-O-alkyl-2-[3H]arachidonoyl-sn-glycero-3-phosphocholine and a significant increase in 1-O-alk-1′-enyl-2-[3H]arachidonoyl-sn-glycero-3-phosphoethanolamine molecular species of over 300%. Thus, HPLC methodology indicates that arachidonoyl-containing
molecular species of phosphatidylcholine and phosphatidylethanolamine are the major source of arachidonic acid in thrombin-stimulated
human platelets, while certain ether phospholipid molecular species become enriched in arachidonate. 相似文献
4.
The existence of ether-linked phospholipids, including 1-O-alk-1′-enyl-2-acyl and 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholines and ethanolamines in bonitoEuthynnus pelamis (Linnaeus) white muscle, was investigated by gas chromatography and gas chromatography-mass spectrometry. Chemical ionization
(iso-butane) mass spectrometry of trimethylsilyl ethers derived from the corresponding ether-linked glycerophospholipids proved
effective not only for determining molecular weights but also for structural identification based on the ions [M−R]+, [M−RO]+ and [M+1]+. 1-O-Alk-1′-enyl-2-acyl-sn-glycero-3-phosphocholine and ethanolamine accounted for 3.0–6.0% and 3.6–7.6% of the total glycerophospholipids, respectively.
1-O-Alkyl-2-acyl-sn-glycero-3-phosphocholine and ethanolamine were also determined for one fish and accounted for 1.4% and 0.6% of the total
glycerophospholipids, respectively. The predominant long chains in thesn-1 position of the glycerol moieties were 16∶0, 18∶0 and 18∶1 in the case of the alkenylacyl and alkylacyl components. Fatty
acid distribution of individual glycerophospholipids was also determined. 相似文献
5.
In mammalian systems, platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, (PAF) is rapidly inactivated by a deacetylation/reacylation system that produces 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine which is highly enriched in arachidonic acid. There is some evidence that n−3 fatty acids may have
an impact on this system in humans but the nature of this impact is unclear. In rainbow trout, n−3 fatty acids are known to
be essential dietary components which are derived through the food chain. Substantial quantities of n−3 fatty acids are found
in trout membrane phospholipids. We show here that in sharp contrast to mammalian cells, trout cells acylate lyso platelet-activating
factor, alkyl-GPC, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine, (lyso-PAF) with a high degree of specificity for n−3 fatty acids. When [3H]lysoPAF was incubated with these cells, only three molecular species of alkylacylglycerophosphocholine were produced, and
92% contained n−3 fatty acids. Since isolated membranes yielded similar results, it appears that the acylation proceedsvia a coenzyme A-independent transacylase as found in mammalian systems. 相似文献
6.
Ether lipid content and fatty acid distribution in rabbit polymorphonuclear neutrophil phospholipids
This study was undertaken to determine if rabbit neutrophils contain sufficient ether-linked precursor for the synthesis of
1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activatin factor) by a deacylation-reacylation pathway. The phospholipids from rabbit
peritoneal polymorphonuclear neutrophils were purified and quantitated, and the choline-containing and ethanolamine-containing
phosphoglycerides were analyzed for ether lipid content. Choline-containing phosphoglycerides (37%), ethanolamine-containing
phosphoglycerides (30%), and sphingomyelin (28%) were the predominant phospholipid classes, with smaller amounts of phosphatidylserine
(5%) and phosphatidylinositol (<1%). The choline-linked fraction contained high amounts of 1-O-alkyl-2-acyl-(46%) and 1,2-diacyl-sn-glycero-3-phosphocholine (54%), with a trace of the 1-O-alk-1′-enyl-2-acyl species. The ethanolamine-linked fraction contained high amounts of 1-O-alk-1′-enyl-2-acyl-(63%) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (34%), and a low quantity of the 1-O-alkyl-2-acyl species (3%). The predominant 1-O-alkyl ether chains found in thesn-1 position of the choline-linked fraction were 16∶0 (35%), 18∶0 (14%), 18∶1 (26%), 20∶0 (16%), and 22∶0 (9%). The major 1-O-alk-1′-enyl ether chains found in thesn-1 position of the ethanolamine-linked fraction were 14∶0 (13%), 16∶0 (44%), 18∶0 (27%), 18∶1 (12%) and 18∶2 (3%). The major
acyl groups in thesn-1 position of 1,2-diacyl-sn-glycero-3-phosphocholine and 1,2-diacyl-sn-glycero-3-phosphoethanolamine were 16∶0, 18∶0 and 18∶1. The most abundant acyl group in thesn-2 position of all classes of choline- and ethanolamine-linked phosphoglycerides was 18⩺2. Although this work does not define
the biosynthetic pathway for platelet activating factor, it does show that there is ample precursor present to support its
synthesis by a deacylation-reacylation pathway. 相似文献
7.
In this study, the 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine content of human platelets was determined. The distribution of arachidonate among the 1,2-diacyl,
1-O-alkyl-2-acyl, and 1-O-alk-l′-enyl-2-acyl classes of choline- and ethanolamine-containing phosphoglycerides was also assessed. The major platelet
phospholipids were choline-containing phosphoglycerides (38%), ethanolamine-containing phosphoglycerides (25%) and sphingomyelin
(18%), with smaller amounts of phosphatidylserine (11%) and phosphatidylinositol (4%). In addition to the diacyl class, the
choline-linked fraction was found to contain both 1-O-alkyl-2-acyl (10%) and 1-O-alk-l′-enyl-2-acyl (9%) species. The ethanolamine-linked fraction, on the other hand, had an elevated level of the 1-O-alk-l′-enyl-2-acyl (60%) species and a small amount of the 1-O-alkyl-2-acyl component (4%). The major fatty acyl residues found in all classes of the choline and ethanolamine phospholipids
were 16∶0, 18∶0, (Δ9), 18∶2(n−6) and 20∶4(n−6). The 1-O-alk-l and 1-O-alk-l′-enyl fraction of the ethanolamine-linked phospholipids also contained substantial amounts of 22∶4(n−6), 22∶5(n−3)
and 22∶6(n−3) acyl chains. Arachidonate comprised 44% of the acyl residues in thesn-2 position of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine. Corresponding values for the diacyl and 1-O-alk-l′-enyl-2-acyl species were 23% and 25%, respectively, based on all 20∶4(n−6) being linked to thesn-2 position of all classes. In the ethanolamine-linked phosphoglycerides, arachidonate constituted 60%, 20% and 68% of the
acyl groups in thesn-2 position of the 1,2-diacyl, 1-O-alkyl-2-acyl and 1-O-alk-l′-enyl-2-acyl classes, respectively. The content of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine appears sufficient to support the synthesis of platelet activating factor by a deacylation-reacylation
pathway in platelets. Our findings also demonstrate that human platelets contain a significant amount of 1-O-alkyl-2-arachidonyl-sn-glycero-3-phosphocholine that could possibly serve as a precursor of both platelet activating factor and bioactive arachidonate
metabolites. 相似文献
8.
Jen-sie Tou 《Lipids》1989,24(9):812-817
This study extended the earlier finding that platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) promotes arachidonic acid incorporation into neutrophil phosphatidylinositol (PI) and phosphatidylcholine
(PC). In the present study the effect of PAF on fatty acid uptake by human neutrophils and the incorporation of extracellular
linoleic acid and palmitic acid into phospholipids were investigated. Incubation of 10−7 M PAF with neutrophils and radiolabeled arachidonic acid or linoleic acid or palmitic acid for 1–10 min resulted in an increased
rate of loss of label from the incubation medium. PAF stimulated the incorporation of linoleic acid and palmitic acid most
significantly into PI and PC. The magnitude of stimulation was greater in PI than in PC for the incorporation of linoleic
acid, and vice versa for the incorporation of palmitic acid. The positional distribution of linoleic acid and palmitic acid
in PI and PC and the mass of these phospholipids were not altered in PAF-stimulated neutrophils. An increased incorporation
of all three fatty acids into both diacyl and alkylacyl species of PC was demonstrated after a two minute incubation of cells
with PAF. While more radioactivity was recovered in the diacyl species, the magnitude of increase of radioactivity in the
alkylacyl species was more pronounced than that in the diacyl species of PC. These results suggest that both increased fatty
acid uptake and increased available lysophospholipids may be contributory to the increased phospholipid acylation induced
by PAF. 相似文献
9.
1-Acyl-2-acetyl-sn-glycero-3-phosphocholine (1-acyl-2-acetyl GPC) was found in the fraction of platelet-activating factor obtained from stimulated
human polymorphonuclear leukocytes (PMN). The amount of 1-acyl-2-acetyl GPC obtained from 1×107 PMN stimulated with ionophore A23187 at 37 C for 15 min ranged from 8 to 56 pmol (32±10 pmol, mean±standard error; n=4).
The main species was 16∶0 palmitoyl (17±5 pmol), followed by 18∶0 stearoyl (8±3 pmol) and 18∶1 oleoyl (7±3 pmol).
Although the physiological significance is unknown, 1-acyl-2-acetyl GPC was always detected when 1-alkyl-2-acetyl GPC was
detected. 相似文献
10.
Molecular species of 1-O-alk-1′-enyl-2-acyl-, 1-O-alkyl-2-acyl-, and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (EPL) andsn-glycero-3-phosphocholine (CPL) of Japanese oysterCrassostrea gigas were analyzed by selectedion monitoring gas chromatography/mass spectrometry using electron impact ionization. The characteristic
fragment ions, [RCH=CH+56]+ due to the alkenyl residue in thesn-1 position and [RCO+74]+ due to the acyl residue in thesn-2 position of alkenylacylglycerols, [R+130]+ due to the alkyl residue in thesn-1 position and [RCO+74]+ due to the acyl residue in thesn-2 position of alkylacylglycerols, [RCO+74]+ due to the acyl residues in thesn-1 and/orsn-2 positions of diacylglycerols, and [M−57]+ being indicative of the corresponding molecular weight, were used for structural assignments.
For alkenylacyl EPL and CPL, 19 and 16 molecular species were determined, respectively. Two molecular species, 18∶0alkenyl-22∶6n−3
and 18∶0-alkenyl-22∶2-non-methylene interrupted diene (NMID), amounted to 53.2% and 47.9%, respectively. The alkylacyl EPL
and CPL consisted of 16 and 20 molecular species, respectively, and the prominent components were 18∶0alkyl-22∶2NMID, 20∶1alkyl-20∶1n−11
(27.4%) and 20∶1alkyl-20∶2NMID (16.3%) in the former, and 16∶0alkyl-20∶5n−3 (23.0%) and 16∶0alkyl-22∶6n−3 (21.6%) in the latter.
For the diacyl EPL and CPL, 14 and 51 molecular species were determined, respectively. The major molecular species were 18∶0–20∶5n−3
(37.4%), 16∶0–20∶5n−3 (14.2%) and 18∶1n−7–22∶2NMID (13.2%) in the former, and 16∶0–20∶5n−3 (33.4%) and 16∶0–22∶6n−3 (22.3%)
in the latter. It was found that there were significant differences in the molecular species between the alkylacyl and diacyl
EPL and the alkylacyl and diacyl CPL; the number of molecular species was larger in CPL than in EPL, while the number of total
carbons and double bonds of the major molecular species were larger in the EPL than in the CPL. Alkenylacyl EPL were similar
to alkenylacyl CPL in molecular species composition. 相似文献
11.
Jiann-Tsyh Lin Carol L. Woodruff Olivier J. Lagouche Thomas A. McKeon Allan E. Stafford Marta Goodrich-Tanrikulu John A. Singleton Carol A. Haney 《Lipids》1998,33(1):59-69
We have examined the biosynthetic pathway of triacylglycerols containing ricinoleate to determine the steps in the pathway
that lead to the high levels of ricinoleate incorporation in castor oil. The biosynthetic pathway was studied by analysis
of products resulting from castor microsomal incubation of 1-palmitoyl-2-[14C]oleoyl-sn-glycero-3-phosphocholine, the substrate of oleoyl-12-hydroxylase, using high-performance liquid chromatography, gas chromatography,
mass spectrometry, and/or thin-layer chromatography. In addition to formation of the immediate and major metabolite, 1-palmitoyl-2-[14C]rici-noleoyl-sn-glycero-3-phosphocholine, 14C-labeled 2-linoleoyl-phosphatidylcholine (PC), and 14C-labeled phosphatidylethanolamine were also identified as the metabolites. In addition, the four triacylglycerols that constitute
castor oil, triricinolein, 1,2-diricinoleoyl-3-oleoyl-sn-glycerol, 1,2-diricinoleoyl-3-linoleoyl-sn-glycerol, 1,2-diricinoleoyl-3-linolenoyl-sn-glycerol, were also identified as labeled metabolites in the incubation along with labeled fatty acids: ricinoleate, oleate,
and linoleate. The conversion of PC to free fatty acids by phospholipase A2 strongly favored ricinoleate among the fatty acids on the sn-2 position of PC. A major metabolite, 1-palmitoyl-2-oleoyl-sn-glycerol, was identified as the phospholipase C hydrolyte of the substrate; however, its conversion to triacylglycerols was
blocked. In the separate incubations of 2-[14C]ricinoleoyl-PC and [14C]ricinoleate plus CoA, the metabolites were free ricinoleate and the same triacylglycerols that result from incubation with
2-oleoyl-PC. Our results demonstrate the proposed pathway: 2-oleoyl-PC. Out results demonstrate the proposed pathway: 2-oleoyl-PC→2-ricinoleoyl-PC→ricinoleate
→triacylglycerols. The first two steps as well as the step of diacylglycerol acyltransferase show preference for producing
ricinoleate and incorporating it in triacylglycerols over oleate and linoleate. Thus, the productions of these triacylglycerols
in this relatively short incubation (30 min), as well as the availability of 2-oleoyl-PC in vivo, reflect the in vivo drive to produce triricinolein in castor bean. 相似文献
12.
The product of the ozonolysis of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine in ethanol-containing solvent was analyzed by chemiluminescence detection-HPLC with on-line electrospray
MS, and characterized on the basis of NMR spectroscopy and MS in high-resolution fast atom bombardment mode. The reaction
yielded a large amount of a novel ethoxyhydroperoxide compound [1-palmitoyl-2-(9-ethoxy-9-hydroperoxynonanoyl)-sn-glycero-3-phosphocholine]. In addition to a structural analysis, we speculate on the reaction pathway and discuss the possibility
of ethoxyhydroperoxide as a potentially reactive ozonized lipid in food and biological materials. 相似文献
13.
Racemic heavy isotope analogs of 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) and 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (PAF) were prepared for use as internal standards to facilitate quantitative studies based on mass
spectrometry. Starting from pentadencane-1,15-diol andrac-glycerol-1,2-acetonide, a convergent synthesis of 1-O-[16′-2H3]hexadecyl and 1-O-[18′-2H3]octadecylrac-glycero-3-phosphocholine and their acetyl derivatives is described. Three deuterium atoms were introduced at the terminal
position of the 1-O-alkyl group by displacement of thep-toluensulfonyl group from 1-O-alkyl-15′-p-toluensulfonate and 1-O-alkyl-17′-p-toluensulfonate with [2H3]-methylmagnesium iodide. The 1-O-alkyl-17′-p-toluensulfonate was obtained by reaction of the 1-O-alkyl-15′-p-toluensulfonate with allylmagnesium bromide, followed by reductive ozonolysis and treatment withp-toluenesulfonyl chloride. The hydroxyl group at C-2 was protected by a benzyl group and removed at a late stage in the synthesis.
This provided the corresponding lysoderivatives or allowed preparation of racemic PAF by subsequent acetylation of the free
hydroxy group. The phosphocholine moiety was introduced at glycerol C-3 by reaction with bromoethyldichlorophosphate and trimethylamine.
The synthetic compounds were analyzed by FAB/MS and GC/NICIMS. They were shown to contain less than 0.6% protium impurity. 相似文献
14.
The molecular species composition of the major glycerophospholipids from white matter of human brain were determined by high-performance
liquid chromatography of the 3,5-dinitrobenzoyl derivatives of the corresponding diradylglycerols. In phosphatidylcholine
(PC) and phosphatidylserine (PS), molecular species containing only saturated fatty acids (SFA) and monounsaturated fatty
acids (MUFA) comprised 85.7 and 82.4% of the respective totals, with 18∶0/18∶1 predominant in PS and 16∶0/18∶1 in PC. These
molecular species were also abundant in phosphatidylethanolamine (PE), but in this phospholipid species containing polyunsaturated
fatty acids (PUFA), largely 18∶0/22∶6n−3 and 18∶0/20∶4n−6, accounted for over half the total; 18∶1/18∶1 was also abundant
in PE. In contrast, 1-O-alk-1′-enyl-2-acylsn-glycero-3-phosphoethanolamine (GPE) had much more SFA- and MUFA-containing species, predominantly 16∶0a/18∶1, 18∶0a/18∶1
and 18∶1a/18∶1, with low amounts of species containing 20∶4n−6 and 22∶6n−3. In alkenylacyl GPE, 22∶4n−6 was the major PUFA
and 16∶0a/22∶4n−6 and 18∶1a/22∶4n−6 the main PUFA-containing species. There was six times more 22∶6n−3, twice as much 20∶4n−6
and half the amount of 22∶4n−6 in PE as compared to alkenylacyl GPE.
Molecular species are abbreviated as follows:e.g., 16∶0/18∶1 PE is 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine; the corresponding alkenylacyl species, 1-O-hexadec-1′-enyl-2-oleoyl-sn-glycero-3-phosphoethanolamine is 16∶0a/18∶1. 相似文献
15.
Vitamin E deficiency was found to stimulate FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine)-induced biosynthesis of PAF
(1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in polymorphonuclear leucocytes (PMN) from rat peritoneum. In three separate experiments each,
the amounts of PAF synthesized during 6min and 12 min incubation of PMN cells from control, vitamin E-supplemented, and vitamin
E-deficient rats were 129–240, 131–227 and 248–354 pmol/106 cells, respectively. The activity of the acetyl-transferase, which transfers the acetyl moiety of [3H]acetyl-CoA to 2-lysoPAF (1-O-alkyl-sn-glycero-3-phosphocholine) to form [3H]PAF, was higher in PMN homogenates from vitamin E-deficient rats (2.28±0.07 nmol/min/mg protein) than in those from E-supplemented
rats (1.06±0.10 nmol/min/mg protein). However, there was no difference between the two groups in the activity of acetylhydrolase
(4.26±0.71 and 4.26±0.06 nmol/min/mg protein, respectively), measured as degradation of [3H]PAF to [3H]lysoPAF.In vitro addition of α-tocopherol did not inhibit the increased activity of acetyl-transferase in vitamin E-deficient rats, in-dicating
that the enzyme in vitamin E-supplemented rats was not directly inhibited by α-tocopherol. The acetyltransferases of the two
groups showed similar Km values for acetyl-CoA, but different Vmax values (225 μM and 6.4 nmol/min/mg protein in vitamin E-deficient
rats, and 216 μM and 3.6 nmol/min/mg protein in vitamin E-supplemented rats), suggesting that the enzyme was not activated
but increased in amount in vitamin E deficiency. 相似文献
16.
Kauffmann I.; Schmidt-Dannert C. 《Protein engineering, design & selection : PEDS》2001,14(11):919-928
The thermoalkalophilic lipase from Bacillus thermocatenulatusBTL2 exhibits a low phospholipase activity (lecithin/tributyrinratio 0.03). A single round of random mutagenesis of the BTL2gene followed by screening of 6000 transformants on egg-yolkplates identified three variants with 1012-fold increasedphospholipase activities, corresponding to lecithin/tributyrinratios of 0.160.36. All variants were specific for thesn-1 acyl ester bond of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine.Mutations occurred predominantly in the N-terminal part of BTL2with regions surrounding the predicted helix 相似文献
17.
The metabolism of 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (1-acyl-PAF), a naturally occurring analogue of platelet activating factor (PAF), was investigated
in rabbit platelets. Our studies showed that 1-acyl-[3H]PAF (1-palmitoyl-2-acetyl-sn-glycero-3-phospho[N-methyl-3H]-choline) was converted by platelets into phosphatidyl-[3H]choline ([3H]PC) in a time-dependent fashion. The formation of [3H]PC occurred at a rate similar to that observed when lyso-[3H]PC (palmitoyl-sn-glycero-3-phospho[N-methyl-3H]choline) was used as substrate. In addition, a time-dependent increase in the level of water-soluble radioactivity was observed
during the incubation of platelets with either 1-acyl-[3H]PAF or lyso-[3H]PC. This increase was parallel to the formation of [3H]PC and was not observed in the presence of [14C]PAF (1-octadecyl-2-acetyl-sn-glycerol-3-phospho[N methyl-14C]choline). Analysis by thin-layer chromatography showed that the soluble radioactivity was mainly associated with glycerophosphocholine
(GPC). On the other hand, the preincubation of platelets with phenylmethylsulfonyl fluoride, an inhibitor of the acetylhydrolase,
reduced the hydrolysis of 1-acyl-[3H]PAF to [3H]GPC with a concomitant accumulation of radioactivity in 1-acyl-PAF. These findings suggest that 1-acyl-PAF is converted
into PC through deacetylation-reacylation with lysoPC as an obligatory intermediate. The findings also indicate that the lysoPC
resulting from 1-acyl-PAF is either reacylated to phosphatidylcholine (PC) or hydrolyzed to GPC by lysophospholipase. Finally,
we showed that the stimulation of platelets with PAF led to a time- and concentration-dependent increase in the conversion
of 1-acyl-[3H]PAF to [3H]PC. The stimulatory effect of PAF was not observed when platelets were lysed before incubation, suggesting that PAF enhances
the metabolism of 1-acyl-PAF, probably by accelerating its translocation through the plasma membrane. 相似文献
18.
In pericytes from bovine retina, the enzyme glycerophosphocholine phosphodiesterase, catalyzing the hydrolysis of sn-glycero-3-phosphocholine to glycero-3-phosphate and choline, has been characterized with respect to pH optimum, metal ion
dependence, K
m, inhibitors, and subcellular localization. In these cells, the natural substrate sn-glycero-3-phosphocholine was present at relatively high concentration (6.4±1.2 nmol/mg protein), and the EDTA-sensitive phosphodiesterase
activity was also found to be markedly high (9.80±1.5 nmol/min/mg protein) compared to the estimated in liver and brain (1–3
nmol/min/mg protein) or in renal epithelial cell culture (0.27 nmol/min/mg protein). The reaction conditions were in general
agreement with those found earlier in brain and other tissues. The majority of the enzyme specific activity was located in
the plasma membrane, whereas a minor part was present in the microsomal fraction. The physiological significance of the high
catabolic phosphodiesterase activity in these cells may be related to the tranfer, followed by deacylation, of lysophosphatidylcholine
from the bloodstream to nervous tissue. In addition, capillary pericytes in culture were able to incorporate 3H-choline rapidly into choline-containing soluble phosphorylated intermediates and into phosphatidylcholine. To find a positive
and negative effector on phosphatidylcholine formation, adenosine, an important intercellular mediator in the retina in response
to alterations in oxygen delivery, and endothelin-1, a potent paracrine mediator present at the blood-brain and blood-retina
barrier, were tested. The cells cultured for 1 or 24 h in a medium containing adenosine at concentrations of 10−6 and 10−4 M showed significant reduction in 3H-choline incorporation compared to control cultures, whereas endothelin-1, at a concentration of 10 and 100 nM, caused stimulation
of phosphatidylcholine biosynthesis. These findings provide evidence that both agonists may modulate phosphatidylcholine metabolism
in pericytes. 相似文献
19.
Junko Sugatani Kazuyo Fujimura Masao Miwa Kiyoshi Satouchi Kunihiko Saito 《Lipids》1991,26(12):1347-1353
The molecular heterogeneity of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (alkylacetyl-GPC) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (acylacetyl-GPC) in normal rat glandular stomach was studied by gas chromatography/mass spectrometry
(GC/MS) and tandem mass spectrometry. The percentage compositions of the molecular species of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC
in the antrum were, respectively. 1-alkyl [16∶0 (34%) and 18∶0 (66%)]-2-acetyl-GPC and 1-acyl [16∶0 (60%), 18∶0 (14%) and
18∶1 (26%)]-2-acetyl-GPC. The alkyl chain composition of 1-alkyl-2-acyl-GPC was quite different from that of 1-alkyl-2-acyl-GPC
in both the antrum and corpus, demonstrating a high degree of selectivity of alkyl chain utilization in PAF biosynthesis.
The amount of 1-acyl-2-acetyl-GPC was much greater than that of 1-alkyl-2-acetyl-GPC. The molecular heterogeneity of 1-alkyl-2-acetyl-GPC
and 1-acyl-2-acetyl-GPC in the corpus was similar to that in the antrum. Water-immersion stress affected not only the amount
of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC, but also their molecular heterogeneity in the antrum and corpus. Whereas
the amounts of 1-hexadecyl-2-acetyl-GPC and 1-acyl [16∶0, 18∶0 and 18∶1]-2-acetyl-GPC decreased markedly (to less than one-fifth)
in the antrum after such stress for 1 hr, the amount of 1-octadecyl-2-acetyl-GPC increased markedly (up to 4-fold) in the
corpus and severe lesions were observed after stress for 7 hr. The changes may be associated with the pathogenicity of gastric
ulcers.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献
20.
A comparative approach has been used to investigate the molecular species composition of phosphatidylcholine (PC) and its
age variation throughout several developmental stages of chick and duck embryo brains. The brain PC consist of 15 major molecular
species which do not undergo appreciable variation in their relative abundance either during embryonic development or between
equivalent stages of maturation in the 2 avian species. In fact, a highly invariable molecular architecture of PC is shown
in the developing organ. Molecular species containing saturated or monounsaturated fatty acids were dominant in all stages
of development of the avian embryo brain. Among these molecular species, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine accounted for 75–80% of the total PC. 相似文献