Molecular Species Of Glycerolipids Research Articles

Reconstruction of Long-Chain Polyunsaturated Acid Synthesis Pathways in Marine Red Microalga Porphyridium cruentum Using Lipidomics and Transcriptomics.

The marine red microalga Porphyridium can simultaneously synthesize long-chain polyunsaturated fatty acids, including eicosapentaenoic acid (C20:5, EPA) and arachidonic acid (C20:4, ARA). However, the distribution and synthesis pathways of EPA and ARA in Porphyridium are not clearly understood. In this study, Porphyridium cruentum CCALA 415 was cultured in nitrogen-replete and nitrogen-limited conditions. Fatty acid content determination, transcriptomic, and lipidomic analyses were used to investigate the synthesis of ARA and EPA. The results show that membrane lipids were the main components of lipids, while storage lipids were present in a small proportion in CCALA 415. Nitrogen limitation enhanced the synthesis of storage lipids and ω6 fatty acids while inhibiting the synthesis of membrane lipids and ω3 fatty acids. A total of 217 glycerolipid molecular species were identified, and the most abundant species included monogalactosyldiglyceride (C16:0/C20:5) (MGDG) and phosphatidylcholine (C16:0/C20:4) (PC). ARA was mainly distributed in PC, and EPA was mainly distributed in MGDG. Among all the fatty acid desaturases (FADs), the expressions of Δ5FAD, Δ6FAD, Δ9FAD, and Δ12FAD were up-regulated, whereas those of Δ15FAD and Δ17FAD were down-regulated. Based on these results, only a small proportion of EPA was synthesized through the ω3 pathway, while the majority of EPA was synthesized through the ω6 pathway. ARA synthesized in the ER was likely shuttled into the chloroplast by DAG and was converted into EPA by Δ17FAD.

Glycerolipid Composition of the Red Macroalga Agarophyton Chilensis and Comparison to the Closely Related Agarophyton Vermiculophyllum Producing Different Types of Eicosanoids.

The red macroalga Agarophyton chilensis is a well-known producer of eicosanoids such as hydroxyeicosatetraenoic acids, but the alga produces almost no prostaglandins, unlike the closely related A. vermiculophyllum. This indicates that the related two algae would have different enzyme systems or substrate composition. To carry out more in-depth discussions on the metabolic pathway of eicosanoids between the two algae, we investigated the characteristics of glycerolipids, which are the substrates of eicosanoids production, of A. chilensis and compared them to the reported values of A. vermiculophyllum. In A. chilensis, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylcholine (PC) were the major lipid classes and accounted for 44.4% of the total lipid extract. The predominant fatty acids were arachidonic acid (20:4n-6), an eicosanoids precursor, and palmitic acid (16:0). The 20:4n-6 content was extremely high in MGDG and PC (>70%), and the 16:0 content was extremely high in DGDG and SQDG (>40%). A chiral-phase HPLC analysis showed that fatty acids were esterified at the sn-1 and sn-2 positions of those lipids. The glycerolipid molecular species were determined by reversed-phase HPLC–ESI–MS analysis. The main glycerolipid molecular species were 20:4n-6/20:4n-6 (sn-1/sn-2) for MGDG (63.8%) and PC (48.2%), 20:4n-6/16:0 for DGDG (71.1%) and SQDG (29.4%). These lipid characteristics of A. chilensis were almost the same as those of A. vermiculophyllum. Hence, the differences of the eicosanoids producing ability between the two algae would not be due to the difference of substrate composition but the difference of enzyme system.

Turnover of Glycerolipid Metabolite Pool and Seed Viability.

Hydration–dehydration cycles can frequently cause stress to seeds, but can also be used to improve germination. However, the molecular basis of the stress caused is poorly understood. Herein, we examine the effects of hydration–dehydration cycles on seed viability and profile the membrane glycerolipid molecular species. We find that seed viability was not affected during the first two cycles, but significantly decreased as further cycles were applied, until all viability was lost. The abundances of seven glycerolipid classes increased and decreased through hydration and dehydration, respectively, but the phosphatidic acid and diacylglycerol abundances changed in the opposite sense, while total glycerolipid contents remained constant. This suggests that during hydration–dehydration cycles, turnover of glycerolipid metabolite pools take place, while no significant lipid synthesis or degradation is involved. As further hydration–dehydration cycles occurred, lipid unsaturation increased, plastidic lipids decreased, and phosphatidylserine acyl chains lengthened. The latter two could be lethal for seeds. Our findings reveal a novel model of membrane lipid changes, and provide new insights into the responses of seeds to hydration–dehydration cycles.

Molecular Species of Glycerolipids from Japonica- and Indeca-types of Brown Rice

Molecular Species of Glycerolipids from Japonica- and Indeca-types of Brown Rice

Lipid Classes, Fatty Acid Composition, and Glycerolipid Molecular Species of the Red Alga <i>Gracilaria vermiculophylla</i>, a Prostaglandin-Producing Seaweed

The red alga Gracilaria vermiculophylla is a well-known producer of prostaglandins, such as PGE2 and PGF2α. In this study, the characteristics of glycerolipids as substrates of prostaglandin production were clarified, and the lipid classes, fatty acid composition, and glycerolipid molecular species were investigated in detail. The major lipid classes were monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG), as well as phosphatidylcholine (PC), which accounted for 43.0% of the total lipid profile. Arachidonic acid (20:4n-6), a prostaglandin precursor, and palmitic acid (16:0) were the predominant fatty acids in the total lipid profile. The 20:4n-6 content was significantly high in MGDG and PC (more than 60%), and the 16:0 content was significantly high in DGDG and SQDG (more than 50%). Chiral-phase high-performance liquid chromatography determined that fatty acids were esterified at the sn-1 and sn-2 positions of those lipids. The main glycerolipid molecular species were 20:4n-6/20:4n-6 (sn-1/sn-2) for MGDG (56.5%) and PC (40.0%), and 20:4n-6/16:0 for DGDG (75.4%) and SQDG (58.4%). Thus, it was considered that the glycerolipid molecular species containing one or two 20:4n-6 were the major substrates for prostaglandin production in G. vermiculophylla.

The Green Microalga Chlamydomonas reinhardtii Has a Single -3 Fatty Acid Desaturase That Localizes to the Chloroplast and Impacts Both Plastidic and Extraplastidic Membrane Lipids

The ω-3 polyunsaturated fatty acids account for more than 50% of total fatty acids in the green microalga Chlamydomonas reinhardtii, where they are present in both plastidic and extraplastidic membranes. In an effort to elucidate the lipid desaturation pathways in this model alga, a mutant with more than 65% reduction in total ω-3 fatty acids was isolated by screening an insertional mutant library using gas chromatography-based analysis of total fatty acids of cell pellets. Molecular genetics analyses revealed the insertion of a TOC1 transposon 113 bp upstream of the ATG start codon of a putative ω-3 desaturase (CrFAD7; locus Cre01.g038600). Nuclear genetic complementation of crfad7 using genomic DNA containing CrFAD7 restored the wild-type fatty acid profile. Under standard growth conditions, the mutant is indistinguishable from the wild type except for the fatty acid difference, but when exposed to short-term heat stress, its photosynthesis activity is more thermotolerant than the wild type. A comparative lipidomic analysis of the crfad7 mutant and the wild type revealed reductions in all ω-3 fatty acid-containing plastidic and extraplastidic glycerolipid molecular species. CrFAD7 was localized to the plastid by immunofluorescence in situ hybridization. Transformation of the crfad7 plastidial genome with a codon-optimized CrFAD7 restored the ω-3 fatty acid content of both plastidic and extraplastidic lipids. These results show that CrFAD7 is the only ω-3 fatty acid desaturase expressed in C. reinhardtii, and we discuss possible mechanisms of how a plastid-located desaturase may impact the ω-3 fatty acid content of extraplastidic lipids.

高度不飽和グリセロ脂質の分子種の分析と機能に関する研究

逆相分配クロマトグラフィーにおける高度不飽和グリセロ脂質分子種の保持容量 (保持時間) を支配する因子, および隣り合うグリセロ脂質分子種の分離度を支配する因子を明らかにし, それらを応用することによって水産グリセロ脂質の内, とくにリン脂質の分子種を同定し, その特徴を明らかにした。次いで, 水産グリセロリン脂質の主要分子種であるDHA結合型リン脂質分子種を合成し, その有用機能の一端として抗腫瘍性物質に対する機能促進性を明らかにするとともに, それを応用したリボソームも作成し, その抗腫瘍性からみた有用性についても評価した。

Biosynthesis of docosahexaenoate-containing glycerolipid molecular species in the retina.

Vertebrate retinas are highly enriched in long-chain polyunsaturated fatty acids (PUFA), especially docosahexaenoic acid (22:6n-3, DHA). In the present study, we investigated the role of de novo synthesis in the enrichment of 22:6n-3 in characteristic molecular species of retinal glycerolipids. Following the incubation of fresh dark-adapted retinas with [2-(3)H]-glycerol, individual glycerolipids were isolated and converted into either diacylglycerol acetates (DGAC) or diacylglycerol benzoates (DGBZ), followed by high-performance liquid chromatography (HPLC) and flow-through radioactivity detection. Total lipids from rat retinas incubated with [3H]-glycerol were analyzed. Unlike what was observed with frog retinas, relative larger of amounts of di-22:6 molecular species were synthesized de novo. In both rat and frog retinas, there was synthesis of glycerolipid molecular species containing two PUFA (one of which was 22:6) in larger amounts than predicted by their steady-state mass levels. These results demonstrate that the unique molecular species of retinal glycerolipids are derived only in part through de novo synthesis, but that molecular rearrangement (remodeling) and differential turnover must also play a role in maintaining the high levels of 22:6 found in rod phohtoreceptor outer segments (ROS) membranes.

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of Gramineae Crops. IV

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of Gramineae Crops. IV

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of Gramineae Crops. III

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of <i>Gramineae</i> Crops. III

Separation and Identification of Plant Glycerolipid Molecular Species by Particle Beam High Performance Liquid Chromatography-Mass Spectrometry

Separation and Identification of Plant Glycerolipid Molecular Species by Particle Beam High Performance Liquid Chromatography-Mass Spectrometry

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of Gramineae Crops. II

Studies on the Molecular Species of Glycerolipids from Some Cereal Seeds of <i>Gramineae</i> Crops. II

Metabolism of lipid molecular species in rat rod outer segments

We have studied the metabolism of selected diacyl molecular species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI) and diacylglycerol (DG) from rat rod outer segments (ROS). Rats were injected intravitreally with [2- 3H]glycerol. At 1, 2, 3, 4 and 6 days post-injection, ROS phospholipids and DG were isolated by two-dimensional thin-layer chromatography (TLC), derivatized, and fractionated into molecular species by high-performance liquid chromatography (HPLC). Selected molecular species were quantitated and counted for radioactivity. We found the following. In PC and PE, the specific activities of 22:6–22:6, 18:1–22:6 and 16:0–22:6 were highest at day 1 and then decreased in a nearly exponential manner. In contrast, the specific activities of 18:2–22:6 and 18:0–20:4 were substantially lower than these three molecular species and changed little over the 6-day period. In PS, the specific activities of 22:6–22:6, 18:0–22:6 and 18:1–22:6 were similar and did not reach their maximum until the 3rd or 4th days. In PC, the specific activities of the five molecular species examined were two to three times higher at day 1 than the same species in PE and PS. In PI and DG, the major molecular species were 16:0–20:4 and 18:0–20:4. The specific activities of these two molecular species at day 1 were about ten times higher than those of 20:4-containing species in PE and PC, and showed the most rapid turnover of any of the molecular species examined in this study. We conclude that each glycerolipid molecular species has a unique rate of biosynthesis and turnover, which determines the steady state level of each species in ROS. Of the three major phospholipid classes (PC, PE and PS), PC is the most metabolically active, as evidenced by the high specific activities in 16:0–22:6, 18:1–22:6 and 22:6–22:6 at day 1, followed by their rapid turnover. We suggest that these molecular species of PC serve as a source of other phospholipids in ROS through base exchange and acyl exchange reactions. The 20:4-containing molecular species of PI and DG are metabolized differently from the same species in PC, PE and PS. The high specific activities at day 1 and the rapid turnover of 16:0–20:4- and 18:0–20:4-PI and -DG suggest an active phosphoinositide turnover in these membranes.

Changes in molecular species of glycerolipids from developing Vigna angularis seeds

The molecular species of six glycerolipids, triacylglycerol (TG), monoglycosyldiacylglycerol (MGDG), diglycosyldiacylglycerol (DGDG), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylinositol (PI) of developing Adzuki bean seeds were studied. The amounts of the six glycerolipids increased gradually until 40 days after flowering, and thereafter decreased. During seed development, the major molecular species of TG were palmitoyllinoleoyllinolenin, palmitoyldilinolenin, dilinoleoyllinolenin, palmitoyldilinolenin and linoleoyldilinolenin. The major molecular species of the diacylglycerol residue in PC, PE and PI were palmitoyllinolein, dilinolein, palmitoyllinolenin and their relative proportions differed slightly. The percentages of the molecular species in TG, PE, PC and PI during seed development varied slightly, while those of MGDG and DGDG varied sharply from 40 to 50 days after flowering.

Quantitative analysis of retinal glycerolipid molecular species acetylated by acetolysis.

A method for the quantitative analysis of molecular species of 1,2-diacylglycerol acetates (1,2-DGAC) containing polyunsaturated fatty acids is described. Phosphatidylethanolamine (PE) isolated from frog retina was used to test the method. PE was converted to 1,2-DGAC by acetolysis. The molecular species of the 1,2-DGAC were resolved by reverse-phase high performance liquid chromatography (HPLC), detected by UV absorption spectroscopy at 210 nm, and identified by gas-liquid chromatography (GLC) of the fatty acid methyl esters (FAME). Molar response curves were generated for each DGAC molecular species that eluted as a single entity from HPLC by determining the moles of fatty acids in the molecular species collected and the response (peak area unit) of the UV detector. Each molecular species response curve was linear from about 10 pmoles to 4-8 nmoles, allowing the slope of each curve to be used as a molar absorptivity. This method provides a means for quantification of most of the molecular species of all glycerolipid classes.

Molecular species of glycerolipids of Ehrlich ascites cells and of their fat granules.

Ehrlich ascites cells were grown in mice and were isolated by centrifugation of the ascites fluid. The cells were lysed with distilled water, and the floating fat particles were collected by centrifugation. The particles contained about 90% neutral and 10% polar lipid. The neutral lipid was made up of about 50% triacylglycerol, 30% alkyldiacylglycerol, 3% cholesteryl esters, 3% free cholesterol and 4% free diacylglycerols. The phospholipid fraction was comprised of about 50% phosphatidylcholine, 35% phosphatidylethanolamine, 10% sphingomyelin and small amounts (less than 5% total) of serine and/or inositol phosphatides. The triacylglycerol and alkyldiacylglycerol fractions possessed total carbon number and fatty acid compositions closely similar to those reported in the literature for whole ascites cells and for a cell membrane preparation. Likewise, the fatty acid composition of phospholipids from the granules in general was similar to that reported for Ehrlich ascites cells. On the basis of the polar and neutral lipid ratio, the lipid granules of the ascites cells were calculated to possess lipid core diameters of 30-50 nm, which were 40-70 times smaller than those (up to 2 mu) measured for the lipid granules of the intact cells by electron microscopy. The characterization of the lipid composition of the Ehrlich ascites lipid granules was completed by determining the molecular species composition of the diacyl, alkylacyl and alkenylacyl phosphatidylethanolamines and of the diacyl and alkylacyl phosphatidylcholines of the ascites cells. It is concluded that the alkyldiacylglycerols of the Ehrlich ascites cells occur largely in the cytoplasmic lipid granules, which appear to consist of many particles of the size and structure of very low density lipoproteins enclosed in membranous sacs.

Linolenic acid biosynthesis via glycerolipid molecular species in pea and spinach leaves

Only molecular species of the eukaryotic type (18:3/18:3; 18:2/18:3; 18:2/18:2, 16:0/18:3, etc…) are present in the phosphatidylcholine (PC) of pea or spinach leaves. In pea leaves, total monogalactosyldiacylglycerol (MGDG) is mostly represented by two eukaryotic molecular species: 18:3/18:3 (79 mol%) and 18:2/18:3 (9%). In spinach leaves, the prokaryotic molecular species 18:3/16:3 forms 39 mol% of total MGDG; however the eukaryotic species 18:3/18:3 (60 mol%) is dominant. At the end of a 30 min pulse with 14C-oleate, four molecular species of PC were intensively labelled in pea leaves: 18:3/ 14C-18: 1; 18:2/ 14C-18: 1; 16:0/ 14C-18: 1 and 18: 1/ 14C-18: 1. During the following 48 hr chase period, clear precursor-product relationships could be observed between 14C-18: 1 PC and 14C-18:2 PC molecular species on one side and between 14C-18:2 PC and 14C-18:3 PC molecular species on the other side. In spinach leaves the same 14C-18: 1 PC molecular species were labelled more slowly and desaturation was not observed beyond 14C-18:2 PC molecular species. In MGDG from pea leaves, labelled linolenic acid accumulated steadily in 18:3/18:3 MGDG, after a lag time of 1 hr. In MGDG from spinach leaves labelled 18:3/18:2 MGDG was a precursor for labelled 18:3/18:3 MGDG. It is concluded that linolenic acid is synthesized via PC molecular species in the eukaryotic pathway of pea leaves and via MGDG molecular species in the eukaryotic pathway of spinach leaves.

グリセロ脂質の分子種の新たなマトリックスモデル

グリセロ脂質の分子種の新たなマトリックスモデル

A study of the molecular species of diacylglycerol, phosphatidylcholine and phosphatidylethanolamine and of cholinephosphotransferase and ethanolaminephosphotransferase activities in the type ii pneumocyte

The percent distributions of the molecular species of diacylglycerol, phosphatidylcholine and phosphatidylethanolamine in rat whole lung and type II pneumocytes were found to differ significantly. Diacylglycerol from the type II pneumocyte is enriched in the disaturated species and diminished in the polyenoic species compared to whole lung. Type II pneumocyte phosphatidylcholine is enriched in the disaturated species and diminished in all other species compared to whole lung. Relative to whole lung, type II pneumocyte phosphatidylethanolamine is greatly enriched in monoenoic and depleted in polyenoic fatty acid species. Analysis of the fatty acid composition of the molecular species in general indicated differences in relative amounts of fatty acids which were most pronounced in palmitic, palmitoleic, stearic and oleic acids, both within and between type II pneumocyte and whole lung glycerolipids. Significant differences between molecular species also existed within type II pneumocyte glycerolipids. In this cell type, phosphatidylcholine is enriched in disaturated and diminished in monoenoic species compared to diacylglycerol. Phosphatidylethanolamine is enriched in monoenoic and polyenoic species relative to diacylglycerol. In order to determine whether differences observed in type II pneumocyte glycerolipid molecular species were attributable to differences in the specificities of cholinephosphotransferase and ethanolaminephosphotransferase, the selectivity of these enzymes was examined. While cholinephosphotransferase showed diminished activity towards 1-stearoyl-2-linoleoyl- sn-glycerol, neither enzyme showed selectivity towards other tested diacylglycerols under a variety of conditions. Therefore, while in the type II pneumocyte significant amounts of phosphatidylcholine (particularly the disaturated species) and phosphatidylethanolamine may be synthesized de novo, enzymes responsible for remodeling (phospholipase A 2 and acyltransferases) may play an important role in establishing the final molecular species composition of both phosphatidylcholine and phosphatidylethanolamine.