Trans-monoenoic and polyunsaturated fatty acids in phospholipids of aVibrio species of bacterium in relation to growth conditions

AVibrio species of bacterium known to contain the polyunsaturated fatty acid 20∶5n−3 was grown in both freshwater and seawater media at 5 and 20°C and examined for adaptive changes in lipid composition. Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), together with a smaller proportion of nonesterified fatty acids (NEFA), comprised almost all the lipid under all growth conditions examined. Temperature had a more pronounced effect than the salinity of the medium on lipid composition. The proportion of PE in total lipid was always higher at 5 than at 20°C. Conversely, the proportion of NEFA was lower at 5 than 20°C whereas that of PG was not altered. The levels of saturated fatty acids in total lipid, PE and PG were all decreased by growth at 5°C. No differences were observed with respect to growth temperature in the levels ofcis 16∶1n−7, the principal monoenoic fatty acid in both PE and PG.Trans 16∶1n−7 was found to comprise 12.8–15.2% of fatty acids in PE and PG of bacteria grown at 5°C but only 4.4–8.5% of phospholipid fatty acids in bacteria cultured at 20°C. Regardless of medium composition, a reduction in growth temperature from 20 to 5°C also caused the proportions of 20∶5n−3 to increase from around 0.8 to 4.4% in PE and from around 4 to 20% in PG. The simultaneous occurrence oftrans 16∶1n−7 and 20∶5n−3 is unique to thisVibrio species of bacterium. The increased proportions of both these fatty acids with decreasing temperature suggest that they have a role in retailoring biomembrane phospholipids during temperature acclimation of the bacterium.     

Generation and remodeling of highly polyunsaturated molecular species of rat hepatocyte phospholipids

Freshly isolated rat hepatocytes were incubated for 20 min with [U-¹⁴C]glycerol in the presence or absence of unlabeled linoleic (18∶2n-6), arachidonic (20∶4n-6), or docosahexaenoic (22∶6n-3) acid, added as albumin complex in 10% ethanol. Most of the radioactivity (≈95%) recovered in hepatocyte lipids was present in phosphatidylcholine (PC), phosphatidylethanolamine (PF), and triacylglycerol (TAG). The presence of exogenous fatty acids resulted in (i) higher incorporation of [U-¹⁴C]glycerol, (ii) higher percentage of label in TAG, and (iii) enhanced formation of PC and PE molecular species bearing the exogenous fatty acid at both the sn-1 and sn-2 positions of glycerol. In each case, these molecular species contained 60 to 70% of the label in that lipid class. Further incubation of the cells for 40 and 80 min in the absence of labeled substrate and exogenous fatty acids resulted in a redistribution of label among PC and PE molecular species due to deacylation-reacylation at the sn-1 position of glycerol.     

Relationship between dietary supply of long-chain fatty acids and membrane composition of long- and very long chain essential fatty acids in developing rat photoreceptors

The present study was designed to determine if dietary supply of long-chain fatty acid (LCFA, C20∶4n-6, and/or C22∶6n-3), reflecting levels that might be incorporated into infant formulas, influences the fatty acid composition of the visual cell membrane. The rod outer segment (ROS) of the retina was analyzed from rats fed diets varying in the ratio of 18∶2n-6 to 18∶3n-3 with or without 20∶4n-6 [arachidonic acid (AA)] and 22∶6n-3 (docosahexaenoic acid) from birth to six weeks of age. The level of very long chain fatty acids (VLCFA, C₂₄−C₃₆) was identified using gas chromatography and gas chromatography-mass spectrometry. In the ROS, the highest relative percent of AA was attained in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of animals fed 1% AA diet, whereas feeding 0.7% docosahexaenoic acid (DHA) diet significantly increased the DHA level in PC, phosphatidylserine, and phosphatidylinositol compared to feeding diets containing AA. VLCFA of n-6 and n-3 up to C₃₆ were found in PC, with the most abundant fatty acids being C₃₂ and C₃₄. In PC, phosphatidylserine and PE, the n-6 tetraenoic VLCFA level was highly increased in animals fed 1% AA compared to other dietary groups. This study suggests that dietary fat containing small amounts of AA or DHA is an important factor influencing membrane fatty acid composition of the visual cell during development. Based on a presentation at the AOCS Annual Meeting & Expo in San Antonio, Texas, May 7–11, 1995.     

Phospholipid composition of the granular amebocyte from the horseshoe crab, Limulus polyphemus

The phospholipid composition was determined for the amebocyte of the primitive arthropod Limulus polyphemus. The total fatty acid composition of the cells' lipids was analyzed by gas chromatography/mass spectrometry (GC/MS) of fatty acid methyl esters (FAME). The FAME analysis revealed high levels of 20-carbon polyunsaturated fatty acids (PUFA), especially arachidonic (20∶4n-6) and eicosapentaenoic (20∶5n-3) acids. Almost 20% of the total lipid profile was comprised of dimethyl acetals of 16- to 20-carbon chain lengths, indicative of plasmalogens in the phospholipid pool. Phospholipids, analyzed by high-pressure liquid chromatography, included phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SPH), and cardiolipin (CL). PE and PC levels predominated at 42.2 and 36.3%, respectively. Smaller amounts of PS (9.0%) and PI (6.2%) were present, as well as low levels of SPH (4.6%), CL (1.6%), and trace amounts of lysophosphatidylcholine. The major phospholipid species, PE, PC, PS and PI, were collected and their molecular species were examined by electrospray-ionization mass spectrometry. The molecular species within the phospholipid classes reflected the high levels of PUFA seen in the total lipid profile. PI was mainly composed of 18∶0a/20∶4. Over half of the PS consisted of 18∶0a/18∶1 and 18∶0a/20∶4. The major PE species were 20∶1p/20∶5, 20∶1p/20∶4, 18∶0p/20∶5, and 18∶0p/20∶4. PC had the largest distribution of molecular species, and its most abundant species were 16∶0e/20∶5, 16∶0e/20∶4, and 16∶0p/20∶4. The presence of 16∶0e/20∶4 is the first documentation of a specific precursor to platelet-activating factor in an invertebrate hemocyte. Note: at the sn-1 position: [a=1=O-acyl, e=1-O-alkylether, and p=1-O-alk-1′-enyl (plasmalogen)].     

Membrane lipid profile of an edible basidiomycete <Emphasis Type="Italic">Lentinula edodes</Emphasis> during growth and cell differentiation

The basidiomycetous mushroom Lentinula edodes (Shiitake) exhibits a unique process of cell differentiation termed “fruiting-body formation”. To clarify the relationship between membrane lipids and fruiting-body formation in this fungus, we investigated variations in levels of phospholipids, cerebrosides, fatty acyl residues in the major phospholipids, and fatty acyl and sphingoid base residues in cerebrosides during vegetative growth and fruiting-body formation. PC, PE, and PS were the primary phospholipids in the cells of L. edodes. After a shift in growth temperature of L. edodes mycelia has been shifted from 25 to 18°C, the proportion of unsaturated FA (UFA), such as linoleic acid (18∶2) and oleic acid (18∶1), increased. In contrast, during fruiting-body formation induced by the temperature downshift to 18°C, 18∶2 of PC in the primordia and fruiting bodies decreased, and the UFA of PF and 18∶1 of PC increased compared with the proportions in mycelia growing at 18°C. These results showed that the proportions of fatty acyl residues in PC and PE differed during fruiting-body formation in L. edodes. Moreover, the amount of cerebrosides in primordia increased compared with those in mycelia and fruiting bodies and, in these differentiating tissues, the proportion of 2-hydroxypentadecanoic acid increased whereas that of 2-hydroxyoctadecanoic acid decreased compared with that in the mycelia. However, the proportion of sphingoid base residues in cerebrosides did not change during fruiting-body formation in L. edodes.     

Effect of temperature on the incorporation into phospholipid classes and metabolismvia desaturation and elongation of n−3 and n−6 polyunsaturated fatty acids in fish cells in culture

The incorporation of 18∶2n−6, 18∶3n−3, 20∶4n−6 and 20∶5n−3 was greater at 10°C than at 22°C in Atlantic salmon (AS), rainbow trout (RTG-2) and turbot (TF) cells. However, there were generally no significant differences between the amount of incorporation of all four polyunsaturated fatty acids (PUFA) into total lipid within a cell type at either 22°C or 10°C. The distributions of the PUFA between individual phospholipid classes at 22°C was essentially the same in AS and TF cells—with the C₁₈ PUFA the order of incorporation in these cells was phosphatidylcholine (PC) > phosphatidylethanolamine (PE) > phosphatidic acid/cardiolipin (PA/CL); with 20∶4n−6 the order was PE and phosphatidylinositol (PI)>PC; with 20∶5n−3, PE>PC. In RTG-2 cells at 22°C the distributions of the C₁₈ PUFA were similar to the other cell lines, but with 20∶4n−6 the order was PC>PI>PE, and with 20∶5n−3 it was PC>PE. At 10°C the incorporation of C₁₈ PUFA into PC increased and into PE and PA/CL decreased, in general, in all cell lines. Incorporation of 20∶5n−3 into PC and PE was increased and decreased at 10°C, respectively, in AS and TF cells, whereas in RTG-2 cells the changes at 10°C were opposite i.e., increased in PE and decreased in PC. With 20∶4n−6, incorporation into PC at 10°C was increased in all cell lines with decreased incorporation into PI in AS and RTG-2 cells and into PE in AS and TF cells, whereas incorporation of 20∶4n−6 into PE increased in RTG-2 cells. The metabolismvia desaturation and elongation of the n−3 PUFA was greater than that of the equivalent n−6 PUFA in all cell lines, irrespective of temperature. There was less conversion of the C₁₈ PUFA at 10°C than at 22°C in RTG-2 and TF cells, but the conversion of 18∶3n−3 by AS cells was increased at 10°C. Temperature had no effect on the conversion of the C₂₀ PUFA.     

Effect of growth temperature on the positional distribution of eicosapentaenoic acid andrans hexadecenoic acid in the phospholipids of aVibrio species of bacterium

Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were isolated from aVibrio species of bacterium, known to produce eicosapentaenoic acid (20∶5n−3) andtrans-hexadecenoic acid (16∶1n−7), and subjected to phospholipase A₂ degradation to determine the positional distribution of component fatty acids. At the two growth temperatures studied (20 and 5°C), both 20∶5n−3 andtrans 16∶1 n−7 were located mainly at positionsn−2 in PE. Increases in the proportions of 20∶5n−3 andtrans 16∶1n−7 in positionsn−2 with decreasing growth temperature were balanced mainly by decreases in the level ofiso-15∶0. In PG,trans 16∶1n−7 was located predominantly in positionsn-1, although the difference between the two positions was not as great as in PE. Eicosapentaenoic acid was preferentially located in positionsn-2 of PG, particularly at 5°C when it comprised 29.9% of the total fatty acids in this position. It is concluded thattrans 16∶1n−7/20∶5n−3 is not a major molecular species of phospholipid in this species ofVibrio and that changes in the levels of molecular species of PE containingiso-15∶0 may feature in thermal acclimation.     

Molecular speciation of fish sperm phospholipids: Large amounts of dipolyunsaturated phosphatidylserine

The molecular species compositions of the main diacyl phosphoglyceride classes and ether-linked subclasses from sperm of three species of fish, sea bass Dicentrarchus labrax, Atlantic salmon Salmo salar and Chinook salmon Onchorhynchus tsawytscha, were determined. The phospholipids from sperm were highly unsaturated, dipolyunsaturated fatty acid (diPUFA) molecular species comprised 64.6 to 71.8% of phosphatidylserine (PS), 10.1 to 17.4% of phosphatidylethanolamine (PE), and 3.3 to 10.1% of phosphatidylcholine (PC). In sea bass sperm, di22∶6n-3 phospholipid was the predominant diPUFA molecular species, but in both salmon species 22∶5n-3/22∶6n-3 was also a major constituent of PS. Phospholipids containing 22∶6n-3 dominated in sea bass sperm with 16∶0/22∶6n-3 as a major component of PC and PE, and 18∶0/22∶6n-3 of PE and PS in addition to di22∶6n-3 in the latter two classes. In contrast, both salmon species contained much more 20∶5n-3 and less 22∶6n-3 so that saturated/20∶5n-3 and monounsaturated/20∶5n-3 molecular species were more abundant than the corresponding molecules containing 22∶6n-3. Ether-linked lipids comprised 11.3–36.3% of choline and ethanolamine phosphoglycerides in each fish species. Molecular species containing 22∶6n-3 were the major components of 1-O-alkyl-2-acyl-glycerophosphocholine, especially 16∶0a/22∶6n-3 in sea bass and 18∶1a/∶6n-3 in the two salmon species, while in 1-O-alk-1′-enyl-2-acyl-glycerophosphoethanolamine, 16∶0a/22∶6n-3 was the major component in both salmon and 18∶0a/22∶6n-3 in sea bass with 18∶1a/22∶6n-3 abundant in all three species. In Atlantic salmon 1-O-alkyl-2-acylglycerophosphoethanolamine comprised 24.6% of ethanolamine glycerophospholipids which were predominantly 16∶0a/22∶6n-3 and 18∶1a/22∶6n-3. Phosphatidylinositol from sperm was dominated by stearoyl/C₂₀ PUFA molecular species, in sea bass overwhelmingly 18∶0/20∶4n-6, while in both salmon species 18∶0/20∶4n-6 and 18∶0/20∶5n-3 were equally abundant.     

Fatty acid composition of subcellular particles from sheep platelets and topological distribution of phosphatidylethanolamine fatty acids in the plasma membrane

The fatty acid composition of individual phospholipids in subcellular fractions of sheep platelets and the asymmetrical distribution of phosphatidylethanolamine (PE) fatty acyl chains across the plasma membrane were examined. The main fatty acids of total lipid extracts were oleic (18∶1; 32–41%), linoleic (18∶2, 10–17%), stearic (18∶0; 13–15%), palmitic (16∶0; 11–15%) and arachidonic (20∶4; 8–12%) acids, with a saturated/unsaturated ratio of about 0.4. Each phospholipid class had a distinct fatty acid pattern. Sphingomyelin (SM) showed the highest degree of saturation (50%), with large proportions of behenic (22∶0), 18∶0 and 16∶0 acids. The main fatty acid in PE, phosphatidylserine (PS) and phosphatidylcholine (PC) was 18∶1n−9. Our findings suggest that fatty acids are asymmetrically distributed between thecholineversus the non-choline phospholipids, and also between plasma membranes and intracellular membranes. The transbilayer distribution of PE fatty acids in plasma membranes from non-stimulated sheep platelets was investigated using trinitrobenzenesulfonic acid (TNBS). A significant degree of asymmetry was found, which is a new observation in a non-polar cell. The PE molecules from the inner monolayer contained higher amounts of 18∶2 and significantly less 18∶1 and 20∶5 than those found in the outer monolayer, although no major differences were detected in the transbilayer distribution of total unsaturatedversus saturated PE acyl chains.     

Molecular species composition of the major diacyl glycerophospholipids from muscle,liver, retina and brain of cod (Gadus morhua)

The molecular species composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) from white muscle, liver, retina and brain of cod (Gadus morhua) were determined by high-performance liquid chromatography of the respective 1,2-diacylglycerol 3,5-dinitrobenzoyl derivatives. A minimum of 69 diacyl species was identified. In muscle and liver saturated fatty acid/polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid/PUFA molecular species were predominant, particularly 16∶0/20∶5 and 16∶0/22∶6 in PC, 16∶0/22∶6 and 18∶1/22∶6 in PE and 18∶0/22∶6 and 18∶1/22∶6 in PS. Didocosahexaenoyl species were major components of PC, PE and PS from retina, comprising 29.3, 71.8 and 59.7% of the respective totals. Didocosahexaenoyl species were also abundant in PE and PS from brain, accounting for 13.8 and 24.0% of the totals, respectively. DiPUFA species were important in muscle, totalling 21.2% in PC and 38.3% in PE. PC from all tissues had the largest amounts of species containing only saturated or monounsaturated fatty acids, accounting for 59.8% of PC from brain, including 12.8% of 18∶1/24∶1 plus 24∶1/18∶1.     

Lipidic characterization of full-grown amphibian oocytes and their plasma membrane-enriched fractions

The content and composition of neutral lipids and phosphoglycerides from full-grown prophase-arrestedBufo arenarum Hensel oocytes and from their ghost preparations were studied. The ghosts obtained are highly enriched in plasma membrane as suggested by the activity of 5′-nucleotidase, a marker enzyme, and the level of typical membrane components such as sphingomyelin, phosphatidylserine (PS), phosphatidylinositol (PI), and phosphatidic acid. In whole oocytes, triacylglyceride (TAG) comprises about 60% of the total lipids followed by phosphatidylcholine (PC), cholesterol, and phosphatidylethanolamine (PE). TAG and diacylglycerides have a similar unsaturation index. PC and PE account for about 80% of the phosphoglycerides in the whole oocyte and in their plasma membrane-enriched fractions. Arachidonic acid (20∶4n−6), 18∶0, and 16∶0 make up about 80 mol% of the total fatty acids in Pl in whole oocytes and ghost fractions. The unsaturation index in PS is higher in intact oocytes than in ghost preparations, probably owing to the significant amount of 20∶4n−6 which comprises 23 mol% of the total fatty acids in whole oocytes. The fatty acid profile in phosphatidic acid from whole oocytes is rather different from that in ghosts. Sphingomyelin contains mainly saturated and monounsaturated fatty acids, 24∶1 being the principal very long chain unsaturated fatty acid in both oocytes and ghosts.     

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20∶5n−3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18∶2n−6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n−3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2∶0.6∶1.0) than reference diets (P/M/S ratio 1∶1∶1) and this was true for both PE (33.4±1.0%vs 24.3±1.1%) and PC (9.3±0.5%vs 4.9±0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20∶5n−3 was preferentially incorporated into PE (10.8±0.2%, 6.0±0.02%) while smaller amounts were incorporated into PC (6.9±0.4%, 3.2±0.2%). The major n−3 polyunsaturated fatty acid found in PE in response to dietary 20∶5n−3 was the elongation metabolite 22∶5n−3 in both the atherogenic (17.7±0.7%) and reference (14.3±1.0%) dietary groups; 22∶6n−3 levels were less affected by diet (4.7±0.3% and 3.9±0.2%, respectively). The results can be interpreted to indicate an inverse relationship between the amount of dietary 18∶2n−6 and incorporation of 20∶5n−3 into erythrocyte membrane phospholipids regardless of whether the major dietary n−3 fatty acid was α-linolenate (18∶3n−3) or 20∶5n−3. This interpretation is supported by theoretical calculations.     

Nuclear magnetic resonance investigation of hydrocarbon chain packing in bilayers of polyunsaturated phospholipids

²H nuclear magnetic resonance (NMR) on chaindeuterated phospholipids has been used to study the influence of the degree of unsaturation on lipid chain packing and on area per molecule at the lipid water interface. Order and motions of deuterated stearic acid in position sn-1 of phosphatidylcholines (PC) containing 18∶0, 18∶1n-9, 18∶2n-6, 18∶3n-3, 20∶4n-6, 20∶5n-3, or 22∶6n-3 in position sn-2 were investigated in pure PC and in mixtures of PC in a phosphatidylethanolamine (PE) matrix. Results reveal that lipid packing in bilayers is mainly controlled by packing requirements at the lipid water interface. Increasing degrees of unsaturation lower chain order and increase area per PC molecule, whereas inclusion of PE in model membranes has the opposite effect. Chain order and motions in highly unsaturated lipid membranes are less sensitive to changes in temperature. Temperature sensitivity decreases further upon incorporation of PC into a PE matrix. Unsaturation induces chain disordering, which may be interpreted as an increase in area per molecule of lipids toward the center of the bilayer. This may result in a lower packing density of unsaturated lipids at the lipid water interface. We hypothesize that these differences in lipid packing and dynamics may influence activity of membrane proteins.     

Phospholipid content and fatty acid composition of human heart

Phospholipid content and fatty acid composition of human heart were determined on 36 biopsy specimens collected during open heart surgery. The main phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG), and sphingomyelin (SPH) were separated by HPLC, quantified, and converted to fatty acid methyl esters which were chromatographed on capillary GLC columns. Sex and age (mainly 40–70) of patients had no significant influence on the relative distribution of phospholipid classes and only a slight effect on fatty acid composition. Incorporation oftrans 18∶1 in phospholipid classes was low.cis andtrans octadecenoic isomers seemed to be selectively incorporated, the Δ9 and Δ11cis ortrans isomers being predominant. Human and rat data were compared, and some species differences were noticed. In human PC, palmitic acid is higher and stearic acid much lower than in rat PC. Saturated dimethyl acetals (16∶0 and 18∶0) in PC and PE were greater for humans. Incorporation of 20∶4 n−6 in human PE is higher than in rat PE.     

Fatty acid composition of 19 species of fish from the black sea and the Marmara Sea

Evidence suggests that differences in fatty acid composition among various fish species may be due to differences in diet or to environmental factors such as temperature, salinity, and depth at which the fish are caught. The beneficial effects of a diet containing fish on cardiovascular or other diseases have been associated with their high content of eicosapentaenoic (20∶5n-3) and docosahexaenoic (22∶6n-3) acids. In this study we analyzed the fatty acid composition of the flesh of 18 different species of marine fish and of cultured rainbow trout. The fish were obtained from the Black and the Marmara Seas, both of which have unique biological and ecological systems as well as eutrophication and pollution. The contents of 20∶5n-3 and 22∶6n-3 in the marine fish ranged from 4.2 to 13.3 wt% of total fatty acids, and from 6.6 to 40.8 wt%, respectively. The most important differences from other studies on oceanic fish were the tendencies toward higher percentages of 16∶0 and 22∶6n-3. The n-3 series of polyunsaturated fatty acids were present as 32.4±1.9% of the total fatty acids. The present study suggests that mature and immature Pomatomus saltator, as well as Engraulis encrasicolus, Mullus surmuletus, Sardina pilchardus, Mugil cephalus, and Sarda sarda may be preferred for the Turkish diet as a result of their high 20∶5 n-3 and 22∶6 n-3 contents. The cultured rainbow trout Oncorhynchus mykiss is not as good a source of n-3 fatty acids as are the marine fish.     

Production of 5,8,11-cis-eicosatrienoic acid by a Δ12-desaturase-defective mutant ofMortierella alpina 1S-4

A mutant defective in Δ12-desaturase of an arachidonic-acid producing fungus,Mortierella alpina 1S-4, was shown to be a novel potent producer of Mead acid (5,8,11-cis-eicosatrienoic acid, 20:3ω9). The fungus produced several fatty acids of the n-9 family,i.e., 6,9-cis-octadecadienoic acid (18:2ω9), 8,11-cis-eicosadienoic acid (20:2ω9) and 20:3ω9. Significantly high levels of these fatty acids were produced during growth at low temperatures (12–20°C). On submerged cultivation at 20°C for 10 days in a 5-L fermenter containing 2% glucose plus 1% yeast extract (pH 6.0), the production of 20:3ω9 reachedca. 0.8 g/L (56 mg/g dry mycelia), accounting for 15% (by wt) of the total mycelial fatty acids. The other major fatty acids were palmitic acid (6%), stearic acid (11%), oleic acid (45%), 18:2ω9 (12%) and 20:2ω9 (3%). Studies on the distribution of fatty acids among lipid classes showed that, irrespective of the growth temperature employed (12–28°C),ca. 70% (by mol) of 20:3ω9 was present in the triglyceride and the remainder in the phospholipid fraction, especially in phosphatidylcholine (PC). When the fungus was grown at 12°C, the proportion of 20:3ω9 in the PC fraction wasca. 55%. On leave from Suntory Ltd.     

(n−3) and (n−6) polyunsaturated fatty acids in the phosphoglycerides of salt-secreting epithelia from two marine fish species

Fatty acid analyses were carried out on phosphoglycerides isolated from microsomal fractions of the rectal gland of the dogfish,Scyliorthinus canicula, and gills of the cod,Gadus morhua. Ratios of (n−3)/(n−6) polyunsaturated fatty acids were ca. 10 for phosphatidylcholine, (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) from cod gills, reflecting high concentrations of 20∶5 (n−3) and 22∶6(n−3). The ratio for phosphatidylinositol (PI) from cod gills was 1.3, reflecting high concentrations of 20∶4(n−6) as well as (n−3) polyunsaturates. PC, PE and PS from rectal glands all had much lower (n−3)/(n−6) ratios than in cod gills, reflecting higher concentrations of 20∶4(n−6), but the lowest ratio was again present in PI. The latter phospholipid had high concentrations of 18∶0 in both tissues. The relative constancy of the fatty acid composition of PI in the two salt-secreting tissues and its similarity to mammalian phospholipids is considered to reflect its specialized role in biomembranes.     

Fatty acid composition of bacteria associated with the toxic dinoflagellate Ostreopsis lenticularis and with caribbean Palythoa species

The fatty acid composition of a Pseudomonas sp. (Alteromonas) and its host, the dinoflagellate Ostreopsis lenticularis, vectors in ciguatera fish poisoning, has been studied. The major fatty acids in O. lenticularis were 16∶0, 20∶5n-3, and 22∶6n-3, but 18∶2n-6, 18∶3n-3, and 18∶n-3 were also identified. In contrast to other dinoflagellates, 18∶5n-3 was not detected in O. lenticularis. Even-chain fatty acids such as 9–16∶1, 11–18∶1, and 13–20∶1 predominated in the Pseudomonas sp. from O. lenticularis, but 16–20% of (E)-11-methyl-12-octadecenoic acid was also identified. The chirality of the latter was confirmed by total synthesis (28% overall yield) starting from oxacyclotridecan-2-one. The fatty acid compositions of two other Pseudomonas species, from the palytoxin-producing zoanthids Palythoa mamillosa and P. caribdea, were also studied and were similar to that of the Pseudomonas sp. from O. lenticularis. The possibility of using some of these fatty acids as chemotaxonomic lipids in identifying marine animals that consume toxic dinoflagellates or zoanthids is discussed.     

Dietary fats containing concentrates ofcis ortrans octadecenoates and the patterns of polyunsaturated fatty acids of liver phosphatidylcholine and phosphatidylethanolamine

The effects of the mixedcis- 18∶1 isomers and mixedtrans-18∶1 isomers present in partially hydrogenated soybean oil (PHSO) upon the patterns of polyunsaturated fatty acids (PUFA) in liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were studied in rats fed concentrates ofcis- 18∶1 ortrans- 18∶1 isomers isolated as triacylglycerides from PHSO. Thecis- 18∶1 andtrans- 18∶1 concentrates were fed at levels equal to those present in PHSO fed at 17.9% of the diet. All diets contained the required amounts of both linoleic and linolenic acids. Thetrans- 18∶1 concentrate was found to suppress the levels of 20∶4ω6 and 20∶3ω9, and to increase the levels of 18∶2ω6 and 20∶5ω3 in PC and PE. Thecis- 18∶1 concentrate suppressed 20∶4ω6 in PC, 20∶5ω3 in PC and PE, and 18∶2ω6 was more effective than thetrans concentrate in suppressing 22∶6ω3. Thetrans- 18∶1 concentrate was more effective in suppressing 20∶4ω6. Thetrans-18∶ isomers appear to modify PUFA metabolism by inhibition of PUFA synthesis, whereas thecis- 18∶1isomers appear to compete with 2-position fatty acyl transfer and to inhibit ω3 PUFA acylation.     

On the specificity of a phospholipase A2 purified from the 106,000×g pellet of bovine brain

Assessment has been made of the specificity of a purified phospholipase A₂ from the 106,000×g pellet (microsomal fraction) of bovine grey matter which shows strong activity toward phosphatidylinositol (PI). In the first series of experiments involving the utilization as substrates of PI with different¹⁴C- or³H-labeled fatty acids in the 2-position, the purified phospholipase A₂ most readily removed 16∶0 palmitic acid, followed by 18∶0 stearic acid, 18∶1 oleic acid and 20∶4 arachidonic acid. In the second series of experiments, the purified phospholipase A₂ showed preferential action toward PI (100%) compared to phosphatidylcholine (PC, 62.5%), phosphatidic acid (PA, 32.6%), phosphatidylethanolamine (PE, 25.1%) and phosphatidylserine (PS, 21.5%), where each phosphoglyceride was labeled in the 2-position with [1-¹⁴C] oleic acid. In the third series of experiments, fatty acids were shown to cause inhibition of action of the purified phospholipase A₂ on 1-acyl, 2-[1-¹⁴C] oleoyl PI in the order 20∶4>18∶1>18∶0>16∶0 which is the reverse order to that just noted. In the final series of experiments, the addition of the phosphoglycerides PC, PE, PS and PA in amounts of 5 or 10 μM caused either no inhibition (PE, 2%), slight inhibition (PC, 15%) or reasonably significant inhibition (PA, 20% and PS, 40%) of action of the purified phospholipase A₂ on 1-acyl, 2-[1-¹⁴C]-oleoyl PI. The pattern of specificity observed for the purified phospholipase A₂ combined with its microsomal location are the expected properties of a phospholipase A₂ that might function in a deacylation-reacylation cycle for modifying the fatty acid distribution in PI.