Lipids of Ectocarpus fasciculatus (Phaeophyceae). Incorporation of [l-14C]Oleate and the Role of TAG and MGDG in Lipid Metabolism

Lipids and fatty acids of Ectocarpus fasciculatus (Ectocarpales,Phaeophyceae) were analyzed. Major polar lipids are monogalactosyldiacylglycerol(MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol(SQDG), diacylglycerylhydroxymethyl-N,N,N-trimethyl-rß-alanine(DGTA), phosphatidylcholine (PC), phospha-tidylethanolamine(PE), phosphatidylglycerol (PG) and phosphatidylinositol (PI).Diphosphatidylglycerol (DPG), phosphatidic acid (PA) and phosphatidyl-O-[N-(2-hydroxy-ethyl)glycine](PHEG) were also present in small amounts. Nonpolar lipids mainlyconsist of triacylglycerol (TAG) and diacylglycerol (DAG). Majorfatty acids are 16:0,18:1, 18:3, 18:4, 20:4 and 20:5. The positionaldistribution of fatty acids showed that molecular species ofeukaryotic structure account for 99% in MGDG, 98% in DGDG, 62%in PG and 23% in SQDG. On incubation with [1-¹⁴C]18:1 for 30min, 33% of the total label was detected in TAG, 16% in PG,14% in PE, 10% in PC and 8% in MGDG. During 7 days of chase,the label in TAG, PG, PE and PC decreased and simultaneouslyincreased in MGDG up to 41% of the total. In SQDG, labelledfatty acids were found in prokaryotic as well as in eukaryoticmolecular species. During the experiment, the label shiftedfrom 18:1 to 18:2, 18:3, 18:4 and, to a minor extent, to 20:4and 20:5 acids indicating 18:1 to be processed by elongationand/or desaturation. These results suggest TAG to act as a majorprimary acceptor of exogenous oleate and to be involved in thetransfer of fatty acids to MGDG and other polar lipids. (Received March 24, 1997; Accepted June 11, 1997)     

Molecular Species of Diacylglycerols and Phosphoglycerides and the Postmortem Changes in the Molecular Species of Diacylglycerols in Rat Brains

The molecular species of 1,2-diacyl-sn-glycerol (DAG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP2) from brains of adult rats (weighing 150 g) were determined. The DAG, isolated from brain lipid extracts by TLC, was benzoylated, and the molecular species of the purified benzoylated derivatives were separated from each other by reverse-phase HPLC. The total amount and the concentration of each species were quantified by using 1,2-distearoyl-sn-glycerol (18:0-18:0) as an internal standard. About 30 different molecular species containing different fatty acids at the sn-1 and sn-2 positions of DAG were identified in rat brains (1 min postmortem), and the predominant ones were 18:0-20:4 (35%), 16:0-18:1 (15%), 16:0-16:0 (9%), and 16:0-20:4 (8%). The molecular species of PC, PE, PS, and PI were determined by hydrolyzing the lipids with phospholipase C to DAG, which was then benzoylated and subjected to reverse-phase HPLC. PIP and PIP2 were first dephosphorylated to PI with alkaline phosphatase before hydrolysis by phospholipase C. The molecular species composition of phosphoinositides showed predominantly the 18:0-20:4 species (50% in PI and approximately 65% in PIP and PIP2). PS contained mainly the 18:0-22:6 (42%) and 18:0-18:1 (24%) species. PE was mainly composed of the 18:0-20:4 (22%), 18:0-22:6 (18%), 16:0-18:1 (15%), and 18:0-18:1 (15%) species. In PC the main molecular species were 16:0-18:1 (36%), 16:0-16:0 (19%), and 18:0-18:1 (14%). Studies on postmortem brains (30 s to 30 min) showed a rapid increase in the total amount (from 40-50 nmol/g in 0 min to 210-290 nmol/g in 30 min) and in all the molecular species of DAG. Comparatively larger increases (seven- to 10-fold) were found for the 18:0-20:4 and 16:0-20:4 species. Comparison of DAG species with the molecular species of different glycerolipids indicated that the rapid postmortem increase in content of DAG was mainly due to the breakdown of phosphoinositides. However, a slow but continuous breakdown of PC to DAG was also observed.     

Fatty acid composition of individual polar lipid classes from marine macrophytes

Major glycolipids [monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG)) and phospholipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG)] as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from Anfeltia tobuchiensis (Rhodophyta), Laminaria japonica, Sargassum pallidum (Phaeophyta), Ulva fenestrata (Chlorophyta) and Zostera marina (Embriophyta), harvested in the Sea of Japan. GC analysis of their fatty acid (FA) composition revealed that the n-6 polyunsaturated FAs (PUFAs) shared the most part of the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG. In algae, it was related to the prevalence of 20:4n-6 over 20:5n-3 in non-photosynthetic lipids. Percentage of n-6 PUFAs as well as the sum of n-3 and n-6 PUFAs decreased in the following sequence: PC-->PE-->PG. The saturation increased in the lines of MGDG-->DGDG-->SQDG and PC-->PE-->PG. PG was close to SQDG by the level of saturation. Distribution of C(18) and C(20) PUFAs in polar lipids depended on taxonomic position of macrophytes. Balance between C(18) and C(20) PUFAs was preferably shifted to the side of C(20) PUFAs in PC and PE that was observed in contrast to glycolipids and PG from L. japonica containing both series of FAs. The set of major FAs of polar lipid classes can essentially differ from each other and from total lipids of macrophytes. For example, MGDG was found to accumulate characteristic fatty acids 16:4n-3, 16:3n-3, 18:3n-6 and 18:4n-3, 20:3n-6 in U. fenestrata, Z. marina, L. japonica and S. pallidum, respectively.     

Effects of Cadmium on Polar Lipid Composition and Unsaturation in Maize （Zea mays） in Hydroponic Culture

This study aimed to evaluate the effect of Cd exposure （100 μmol/L） on polar lipid composition, and to examine the level of fatty acid unsaturation in maize （Zea mays L.）. In roots, the level of 16：0 and monounsaturated fatty acids （16：1 ＋ 18：1） decreased in phosphatidylcholine （PC） and phosphatidylethanolamine （PE）. In contrast, the proportion of unsaturated 18-C fatty acid species showed an opposite response to Cd. The content, on the other hand, of PC, PE, digalactosyldiacylglycerol （DGDG）, and steryl lipids increased in roots （2.9-, 1.6-, 5.3-, and 1.7-fold increase, respectively）. These results suggest that a more unsaturated fatty acid composition than found in control plants with a concomitant increase in polar lipids may favor seedling growth during Cd exposure. However, the observed increase in the steryl lipid （SL） ： phospholipid （PL） ratio （twofold）, the decrease in monogalactosyldiacylglycerol （MGDG） ： DGDG ratio, as well as the induction of lipid peroxidation in roots may represent symptoms of membrane injury. In shoots, the unsaturation level was markedly decreased in PC and phosphatidylglycerol （PG） after Cd exposure, but showed a significant increase in sulfoquinovosyldiacylglycerol （SQDG）, MGDG and DGDG. The content of PG and MGDG was decreased by about 65%, while PC accumulated to higher levels （4.4-fold increase）. Taken together, these changes in the polar lipid unsaturation and composition are likely to be due to alterations in the glycerolipid pathway. These results also support the idea that the increase in overall unsaturation plays some role in enabling the plant to withstand the metal exposure.     

Adaptation of biological membranes to temperature: molecular species compositions of phosphatidylcholine and phosphatidylethanolamine in mitochondrial and microsomal membranes of liver from thermally-acclimated rainbow trout

Summary Molecular species profiles were determined for both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of mitochondrial and microsomal membrane fractions from liver tissue of thermally-acclimated rainbow trout,Salmo gairdneri. The predominant molecular species of PC were 16:0/22:6, 16:0/18:1, 16:0/20:3 and 16:0/22:5, whereas predominant molecular species of PE were 18:1/20:4, 14:0/16:0, 18:0/22:6 and 18:1/22:6. PE possessed short chain saturates (primarily 14:0/16:0) and monoenes (primarily 14:0/16:1) not present in PC and larger proportions of polyunsaturated (18:0/22:6, 18:0/22:5 and 18:1/22:6. and diunsaturated molecular species than PC. Differences between membrane fractions were most evident in warm (20°C)-acclimated trout. Mitochondria contained higher proportions of long-chain, polyunsaturated molecular species of PE, but less of the corresponding species of PC than other membrane fractions. Rankings based on unsaturation index were accordingly: mitochondria heavy microsomes>light microsomes for PE, but heavy microsomes>light microsomes>-mitochondria for PC. Mitochondria were notable for high proportions of diunsaturated molecular species of both phosphatides. Growth at cold temperatures (5°C) was generally associated with a replacement of shorter chain mono- and dienoic molecular species (16:0/18:1, 16:1/18:1, 14:0/16:2 and 18:1/18:1 in the case of PC and 14:0/16:1, 14:0/16:2 and 16:1/18:1 for PE), and occasionally saturates, with long-chain, polyunsaturated molecular species (for PC, C_36–38: 16:0/22:6, 16:1/22:6, 16:0/20:3 and 16:0/20:5; for PE, C_38–40: 18:1/20:4, 16:1/22:6, 18:0/20:5, 18:2/20:4, 18:0/22:5 and 18:0/22:6). However, compositions of mitochondrial PE and PC from heavy microsomes were not significantly influenced by acclimation temperature. The role of phospholipase A₂, in addition to other metabolic processes, in mediating these changes is discussed.Abbreviations ACL average chain length - UI unsaturation index     

Lipid and Fatty Acid Composition of the Marine Brown Alga Dictyopteris membranacea

Glycerolipids and fatty acids of D. membranacea (Dic-tyotales)were analysed. The betaine lipid DGTA and the glycolipids MGOG,DGDG and SQDG were major components. The phospholipids PE, PG,PI and PHEG were present in minor amounts only. This lipid pattern,which is characterised by the presence of DGTA and the absenceof PC, has been found exclusively in brown algae belonging tothe orders Dictyotales, Durvillaeales and Fucales. Major fattyacids were 16:0, 18:1, 18:2, 18:3, 18:4 and 20:4 acids. MGDGwas the most unsaturated lipid with high levels of 18:4 acid.SQDG showed the highest degree of saturation containing a considerableproportion of 16:0 acid. DGTA contained 14 : 0,18:1,18:2 and20:4 as major fatty acids. Among phospholipids, PE and PHEGhad a very similar pattern which was enriched in 20:4 acid.Analysis of the positional distribution of fatty acids revealedthat DGTA and MGDG were almost exclusivly of the "euka-ryotic"type, whereas SQDG was predominantly of the "prokaryotic" type.For the first time, molecular species of selected lipids havebeen analysed in a brown alga. In DGTA, 14:0/18:1, 14:0/18:2and 14:0/20:4 were the main molecular species. In MGDG the highlyunsaturated erl8:3/18:4, 18:4/18:4 and 18:4/20:5 were predominant. (Received March 31, 1997; Accepted July 4, 1997)     

High-performance liquid chromatographic method for determination of the metabolism of polyunsaturated molecular species of phosphatidylserine labeled in the polar group

A reversed-phase HPLC method to monitor the incorporation of radiolabeled precursors into the polar group of individual polyunsaturated molecular species of phosphatidylserine (PS) is presented. PS labeled in the polar group was decarboxylated and subsequently converted to trinitrophenyl-phosphatidylethanolamine (Tnp-PE), which was separated into its molecular species by reversed-phase HPLC within 90 min, using a gradient of acetonitrile—methanol and ammonium acetate. A major feature of the method is the complete resolution of the stearoyl species, 18:0/20:4 and 18:0/22:6, at ambient temperature. By determining the amount of radioactivity incorporated into each fraction, the metabolism of individual molecular species of PS, and also of PE, labeled in the polar group can be investigated.     

Phospholipid molecular species of Bacteroides

The fatty acid composition, and types of polar lipid (PL) present, have been well-studied in Bacteroides. Nothing is known, however, of the detailed structures of individual phospholipid and molecular species. The aim of this study was to determine molecular weights and putative identities of individual phospholipid molecular species present in Bacteroides. Thirteen culture collection strains were harvested, washed and freeze-dried. Polar lipids were extracted and separated by conventional fast atom bombardment mass spectrometry (FAB MS). For each strain, hundreds of polar lipid peaks were seen. Nineteen major anions in the range m/z 209–299 were separated. The most intense of these was consistent with the expected presence of the C_15:0 anion. Other anions were attributable to saturated, mono-unsaturated, di-unsaturated, tri-unsaturated and hydroxy-carboxylate ions. Twenty-two major anion peaks were recorded in the range m/z 505–722. These were consistent with the presence of analogues of phosphatidic acid (PA), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). The most intense peaks included those consistent with the presence of PE(30:0), PG(29:1), PG(30:1), PG(28:1), PE(31:0), PE(OH-30:0), PG(31:1) and PE(OH-31:0). This combination of PL molecular species is unique to Bacteroides and has not been reported in other organisms so far examined.     

Lipid Composition of Citrus Leaves from Plants Resistant and Susceptible to Citrus Bacterial Canker

The contents and composition of lipids in citrus leaves in relation to their general resistance to infection by strains of Xanthomonas campestris pv. citri (Xcc) were determined. The composition and contents of total polar lipids and phospholipids and the degree of fatty acid unsaturation were significantly different between resistant and susceptible species. Leaves from resistant plants had less phospholipids, but more free sterols than those from susceptible plants. The predominant fatty acids in the phospholipids were palmitic (16:0), linoleic (18:2) and α-linolenic acid (18:3). The degree of fatty acid unsaturation was higher in susceptible plants than in resistant plants. Major phospholipids in citrus leaves were phosphatidylchloline (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI). β-Sitosterol, campesterol and lanosterol were major sterols in the leaves of citrus plants with resistant species having a higher ratio of free sterols to total phospholipids than susceptible species. Differences in lipid metabolism may contribute to differences in Xcc-resistance of citrus leaves.     

Effects of moderately enhanced levels of ozone on the acyl lipid composition of leaves of garden pea (Pisum sativum)

Plants of garden pea ( Pisum sativum L.) were exposed to charcoal-filtered air with or without addition of 65 ± 5 l⁻¹ ozone. Plants were harvested daily for 9 days and lipids were extracted from the second-oldest leaf. Visible injury of this leaf was evident from day 5 on, while the differences in lipids between ozone and control treatments were observed earlier. Ozone caused large decreases in the contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG), a slower decrease in the content of phosphatidylcholine (PC), but an increase in the content of phosphatidylethanolamine (PE) per leaf area, compared with exposure to charcoal-filtered air. The content of phosphatidylglycerol (PG) was unaffected by ozone. Compared with charcoal-filtered air, fumigation with ozone resulted in a decrease in the proportion of linolenic acid (18:3) of the total lipid extract, with a concomitant increase in the proportion of linoleic acid (18:2). For individual lipids, ozone caused a similar pattern of decreased 18:3 and increased 18:2 in MGDG, SQDG, PC and PE, while the fatty acid composition of DGDG was unaffected. In PG, ozone decreased the proportions of 18:3 and trans -Δ³-decenoic acid (16:1_trans), balanced by increased proportions of palmitic and oleic acids. The contents of chlorophylls and carotenoids were unaffected by ozone. Our results show that moderately elevated levels of ozone cause significant changes in the polar lipid composition of garden pea leaves and in the level of unsaturation of the lipid acyl groups and, furthermore, that ozone has different effects, which could be direct or indirect, on chloroplast lipids (MGDG, DGDG, SQDG, PG acylated with 16:1_trans) and cytosolic membrane lipids.     

Comparative Plasma Lipidome between Human and Cynomolgus Monkey: Are Plasma Polar Lipids Good Biomarkers for Diabetic Monkeys?

Background

Non-human primates (NHP) are now being considered as models for investigating human metabolic diseases including diabetes. Analyses of cholesterol and triglycerides in plasma derived from NHPs can easily be achieved using methods employed in humans. Information pertaining to other lipid species in monkey plasma, however, is lacking and requires comprehensive experimental analysis.

Methodologies/Principal Findings

We examined the plasma lipidome from 16 cynomolgus monkey, Macaca fascicularis, using liquid chromatography coupled with mass spectrometry (LC/MS). We established novel analytical approaches, which are based on a simple gradient elution, to quantify polar lipids in plasma including (i) glycerophospholipids (phosphatidylcholine, PC; phosphatidylethanolamine, PE; phosphatidylinositol, PI; phosphatidylglycerol, PG; phosphatidylserine, PS; phosphatidic acid, PA); (ii) sphingolipids (sphingomyelin, SM; ceramide, Cer; Glucocyl-ceramide, GluCer; ganglioside mannoside 3, GM3). Lipidomic analysis had revealed that the plasma of human and cynomolgus monkey were of similar compositions, with PC, SM, PE, LPC and PI constituting the major polar lipid species present. Human plasma contained significantly higher levels of plasmalogen PE species (p<0.005) and plasmalogen PC species (p<0.0005), while cynomolgus monkey had higher levels of polyunsaturated fatty acyls (PUFA) in PC, PE, PS and PI. Notably, cynomolgus monkey had significantly lower levels of glycosphingolipids, including GluCer (p<0.0005) and GM₃ (p<0.0005), but higher level of Cer (p<0.0005) in plasma than human. We next investigated the biochemical alterations in blood lipids of 8 naturally occurring diabetic cynomolgus monkeys when compared with 8 healthy controls.

Conclusions

For the first time, we demonstrated that the plasma of human and cynomolgus monkey were of similar compositions, but contained different mol distribution of individual molecular species. Diabetic monkeys exhibited decreased levels of sphingolipids, which are microdomain-associated lipids and are thought to be associated with insulin sensitivity. Significant increases in PG species, which are precursors for cardiolipin biosynthesis in mitochondria, were found in fasted diabetic monkeys (n = 8).     

The effect of salt on the lipid composition of Ectothiorhodospira

Major components of polar lipids of halophilic phototrophic Ectothiorhodospira species were PG, CL, PC and PE. PA was only present in minor amounts. According to ¹⁴C-incorporation, polar lipids approximated to 75%–93% of the total lipid carbon. With increasing salinity, a strong increase in the portion of PG and a decrease in that of PE (especially in Ectothiorhodospira mobilis BN 9903) and CL (especially in E. halophila strains) were observed. Moreover, there was a significant increase in the excess negative charges of phospholipids upon increasing medium salinity. This increase was most dramatic in the slightly halophilic E. mobilis BN 9903, but quantitatively less important in both strains of E. halophila which had, however, a higher percentage of negative charges of their lipids. During salt-shift experiments, E. halophila BN 9630 responded to suddenly increased salinity by promoting the biosynthesis of PG and decreasing that of PC, CL and PE. Upon dilution stress, responses were reversed and resulted in a strong increase in PE biosynthesis. The effects of lipid charges and bilayer forming forces in stabilizing the membranes of Ectothiorhodospira species during salt stress are discussed.Abbreviations PC phosphatidylcholine - PG, PG-1, PG-2 phosphatidylglycerol - CL, CL-1, Cl-2 cardiolipin - PE phosphatidylethanol-amine - PA phosphatidic acid - NL nonpolar lipids - ori origin - TLC thin layer chromatography     

Lipid metabolism during aging of high-alpha-linolenate-phenotype potato tubers

Previous studies demonstrated that high levels of alpha-linolenate in cell membranes of potato tubers (achieved by overexpressing fatty acid desaturases) enhances lipid peroxidation, oxidative stress, and tuber metabolic rate, effectively accelerating the physiological age of tubers. This study details the changes in lipid molecular species of microsomal and mitochondrial membranes from wild-type (WT) and high-alpha-linolenate tubers during aging. The microsomal and mitochondrial polar lipids of high-alpha-linolenate tubers were dominated by 18:3/18:3 and 16:0/18:3 molecular species. Relative to WT tubers, high-alpha-linolenate tubers had a substantially higher 16:0/18:n to 18:n/18:n molecular species ratio in mitochondria and microsomes, potentially reflecting a compensatory response to maintain membrane biophysical properties in the face of increased unsaturation. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for 53 and 37% of polar lipids, respectively, in mitochondria from younger WT and high-alpha-linolenate tubers. The relative proportions of these phospholipids (PL) did not change during aging of WT tubers. In contrast, PE increased to dominate the PL pool of mitochondria during aging of high-alpha-linolenate tubers. While aging effected an increase in mitochondrial 18:3-bearing PCs and PEs in WT tubers, the concentration of 18:3-bearing PCs fell with a concomitant increase in 18:3-bearing PEs during aging of high-alpha-linolenate tubers. These age- and high-alpha-linolenate-induced changes had no effect on the respiration rate and functional integrity of isolated mitochondria. Differential increases in the respiration rates of WT and high-alpha-linolenate tubers during aging were therefore a consequence of unsaturation-dependent alterations in the microenvironments of cells. Microsomal 18:3-bearing PCs, PEs, digalactosyldiacylglycerols (DGDG), and monogalactosyldiacylglycerols all increased in WT tubers during aging. In contrast, a selective loss of 18:3-bearing PCs and DGDGs from microsomes of high-alpha-linolenate tubers likely reflects a greater susceptibility of membranes to peroxidative catabolism during aging. Aging resulted in an increase in sterol/PL ratio in microsomes from WT tubers, due primarily to a decline in PL. In high-alpha-linolenate tubers, the increase in sterol/PL ratio during aging was due to increases in Delta 5-avenasterol and stigmasterol, indicating membrane rigidification and likely contributing to increased membrane permeability. Age-induced changes in 18:3-bearing lipids in membranes of transformed tubers are discussed relative to the development of oxidative stress and accelerated aging.     

The molecular species of phospholipids of the cold-water soft coral <Emphasis Type="Italic">Gersemia rubiformis</Emphasis> (Ehrenberg, 1834) (Alcyonacea,Nephtheidae)

The chemical structures and contents of 68 molecular species of ethanolamine glycerophospholipids (PE), choline glycerophospholipids (PC), serine glycerophospholipids (PS), and inositol glycerophospholipids (PI) were determined in the asymbiotic soft coral Gercemia rubiformis (Ehrenberg, 1834) from the Sea of Okhotsk by the method of tandem high-resolution mass spectrometry. The major molecular species were 16:1e/20:4 PE, 16:0e/20:4 PC, 20:1/24:5 PS, and 16:0/24:5 PI. This study showed a significant similarity of the polar lipidomes of G. rubiformis and tropical species of alcyonarians with symbiotic microalgae and revealed the basic characteristic of the polar lipidome of these alcyonarians. It was found that the 24:5n-6 and 24:6n-3 acids (chemotaxonomic markers of soft corals) concentrate in the acyl groups of the molecular species of PS and PI, which can be used as molecular lipid markers in the study of the symbiotic and trophic relationships of soft corals.     

Fatty-acid composition of polar lipids in fruit and leaf chloroplasts of “16:3”- and “18:3”-plant species

The fatty-acid composition of polar lipids from fruit and leaf chloroplasts was compared in five Solanaceous and two cucurbit species. The acylated fatty acids in monogalactosyl diglycerides (MGDG) from leaf chloroplasts of all five Solanaceous species included substantial amounts of ^7,10,13-hexadecatrienoic acid (16:3). In contrast, the MGDG from fruit chloroplasts of the Solanaceae contained very little of this plastid-specific polyunsaturate, and instead included a proportionately greater percentage of linoleic acid (18:2). In MGDG from leaf chloroplasts of two cucurbits, -linolenic acid (18:3) constituted 94–95% of the acylated fatty acids. Fruit-chloroplast galactolipids of the cucurbits had a greater abundance of 18:2, and hence a higher 18:2/18:3 ratio, than found in the corresponding leaf lipids. Among the phosphoglycerides, the unusual fatty acid 3-trans-hexadecenoate (trans-16:1) constituted from 15 to 24% of the acylated fatty acids in phosphatidyl glycerol (PG) from leaf chloroplasts (all species). In sharp contrast, trans-16:1 was virtually absent in PG from fruit chloroplasts of both Solanaceous and cucurbit species, and was replaced by a proportionate increase in the content of palmitate (16:0). The observed differences in the polar lipid fatty-acid composition of fruit and leaf chloroplasts are discussed in terms of the relative activity of several intrachloroplastic enzymes involved in lipid synthesis and fatty-acyl desaturation.Abbreviations MGDG monogalactosyldiglyceride - DGDG digalactosyl diglyceride - PC phosphatidyl choline - PE phosphatidyl ethanolamine - PG phosphatidyl glycerol     

Modulation of the Activity of Purified Tonoplast H+-ATPase from Mung Bean (Vigna radiata L.) Hypocotyls by Various Lipids

H⁺-ATPase was solubilized from the tonoplast of mung bean (Vignaradiata L.) hypocotyls and purified by fast protein liquid chromatographyon a Mono Q ion-exchange column. The purified ATPase hardlycontained any phospholipid, but it did contain 10 to 15 moleculesof sterol and 25 to 30 molecules of glycolipid per ATPase molecule,and it had little activity without exogenously added phospholipids.Each individual polar head group, acylglyceride and fatty acidthat constituted a phospholipid was incapable by itself of activatingthe ATPase. Sterols and cerebroside had little activating effect.Maximal activation of ATPase was noted with asolectin or variousmolecular species of phosphatidylcholine (PC) at 0.005% to 0.01%(w/v). The activation by the various molecular species of PCwas dependent on the length and degree of unsaturation of fattyacyl chains. PC with two saturated and long fatty acyl chainsof more than 18 carbon atoms failed entirely to activate theATPase. PC, PS and PG with 1-palmitoyl (16:0)-2-oleoyl(18:1)fatty acyl chains all activated ATPase to nearly the same extentas asolectin, but the activation by PE and PA with the samefatty acyl composition was 52% and 15% of that by asolectin,respectively. The molecular species of PC with phase-transitiontemperatures below 50C activated ATPase, as determined at 38C.The dependence on temperature of the activation by the molecularspecies of PC indicated that the activation of the ATPase beganclose to the temperature of the phase transition of the PC added.These data indicate that phospholipids in the liquid-crystallinephase are essential for the catalytic activity of the ATPase. (Received June 4, 1992; Accepted January 18, 1993)     

The phospholipid fatty acids of Porphyridium purpureum cultured in the presence of triton x-100 and sodium desoxycholate

The phospholipid fatty acid composition of Porphyridium purpureum grown on a solid medium was studied in the presence of Triton X-100 (TX) and sodium desoxycholate (SDC). The most common fatty acids in PC and PE were palmitic (16:0), stearic (18:0), linoleic (18:2ω6), arachidonic (20:4ω6) and eicosapentaenoic (20:5ω3) acids, 20:4ω6 being very abundant. In PG the most common acids were 16:0, trans-hexaenoic acid (tr16:1ω3), oleic acid (18:1) and 20:4ω6. Both detergents caused an increase in the saturation of PC and, to a lesser extent, of PE. The relative amounts of short chain fatty acids increased. Both detergents increased the amounts of 16:0 and, correspondingly, decreased the amounts of 20:4ω6. In PG the amounts of both 16:0 and tr 16:1ω3 increased and the amounts of 18:0, 18:2ω6 and 20:4ω6 decreased in the presence of detergents. The changes were always greatest at the concentrations of 5–10 ppm TX or SDC. At 20 ppm the fatty acid compositions, especially with SDC, were very similar to the controls, which suggests a change in the detergent effect between 10–20 ppm. The normal PC/PE ratio was 5.6 and the (PC+ PE)/PG ratio 39.0. Both detergents caused a marked decrease in these ratios. Because the detergent effects are not linear, it seems that even very low detergent concentrations have an important influence on algae in polluted waters.     

The influence of ionic detergents on the phospholipid fatty acid compositions of Porphyridium purpureum

The phospholipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). The most common fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were palmitic (16:0), stearic (18: 0), linoleic (18:2ω 6), arachidonic (20:4ω 6) and eicosapentaenoic (20:5ω 3) acids, 20:4ω 6 being very abundant. In phosphatidyl glycerol (PG) the most common acids were 16:0, trans-hexadecenoic acid (tr 16:1ω 13), oleic acid (18:1) and 20:4ω 6. Both detergents increased the saturation grade of PC and PE by decreasing the relative amount of the polyunsaturated acids, especially 20:4ω 6. A corresponding increase in the amounts of saturated acids was observed in PC and PE. The changes in PG fatty acid composition were not very significant: a slight increase was observed in the amounts of 16:0 and tr 16:1ω 13 , with a corresponding decrease in the amounts of 20:4ω 6 and 20:5ω 3. Both detergents decreased the PC/PE and the (PC + PE)/PG ratios very markedly, most probably as a result of increases in the amounts of PE and PG. In the presence of CTAB the cells seemed to contain much more phospholipids than in the presence of SDS, perhaps as a result of the mucilage-precipitating effect of CTAB. The significance of the findings is discussed.     

Microsomal Phospholipid Molecular Species Alterations during Low Temperature Acclimation in Dunaliella

A detailed analysis of the low temperature-induced alterations of Dunaliella salina (UTEX 1644) microsomal membrane lipids was carried out. Microsomal membranes were isolated from cells grown at 30 degrees C, from cells shifted to 12 degrees C for 12 hours, and from cells acclimated to 12 degrees C. Fatty acid analyses of the major lipid classes demonstrated significant changes in the fatty acid composition of phosphatidylcholinemine (PE) and phosphatidylglycerol (PG) but not phosphatidylcholine (PC) during the initial 12 hours at low temperature. These changes did not entail enhanced desaturation of linoleic acid. Subsequent to 12 hours, the proportions of linolenic acid increased in all phospholipids.Molecular species analyses of the phospholipids demonstrated that the most immediate changes following a shift to low temperature were limited to several molecular species of PE and PG. The changes observed in PE included a decrease in C(30) species and concomitant increases in C(34) and C(36) species. Compositional changes associated with PG entailed the emergence of a new molecular species (18:1/18:1) not found at 30 degrees C. The retailoring of molecular species resulted in an increase in the number of species having two unsaturated acyl chains and did not reflect a simple enhancement of desaturase activity as suggested by the fatty acid analysis. We conclude that the initial alterations in response to low temperature stress involve discrete changes in certain molecular species. These and further alterations of molecular species following acclimation to low temperature would appear to augment increases in acyl chain desaturation as a means of modifying membrane properties in response to low temperature stress.     

Selective changes to phosphatidylcholine and phosphatidylethanolamine molecular species in the developing fetal guinea pig liver and plasma

The molecular species composition of membrane phospholipids influences the activities of integral proteins and cell signalling pathways. We determined the effect of increasing gestational age on fetal guinea pig liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE), and plasma PC molecular species composition. The livers were collected from fetuses (n = 5/time point) at 5 day intervals between 40 and 65 days of gestation, and at term (68 days). Hepatic PC and PE molecular species composition was determined by electrospray ionisation mass spectrometry. An increasing gestational age was accompanied by selective changes in individual molecular species. The proportion of the sn-1 18:0 species increased relative to the sn-1 16:0 species in liver PC, but not PE, with an increasing gestational age. 1-O-alkyl-2-acyl PC species concentrations decreased significantly between 40 and 45 days of gestation (40%), and 65 and 68 days (54%). Total 1-O-alkenyl-2-acyl PE species concentration increased between days 60 and 65, due to a rise in 1-O-16:0 alkyl/20:4 content, and then decreased until term. Between day 40 and term, PC and PE sn-2 18:2n-6 species concentrations increased 3-fold. PC16:0/18:2 increased gradually throughout gestation, while PC18:0/18:2 content only increased after day 65. The overall increase in PE18:2n-6 content was due to PE18:0/18:2 alone. The composition of plasma PC essentially reflected hepatic PC. Overall, these data suggest differential regulation of hepatic PC and PE molecular species composition during development which is essentially independent of the maternal fatty acid supply.