Monogalactosyl and digalactosyl diglycerides from heterotrophic, hetero-autotrophic, and photobiotic Euglena gracilis

The lipid of Euglena gracilis, dark-grown in a complete medium, contained 2% galactose. The lipid of Euglena gracilis, light-grown in either a complete or an inorganic medium, contained 13-14% galactose. Pure monogalactosyl and digalactosyl diglyceride fractions, isolated by column plus thin-layer chromatography, contained 50% of the lipid-bound galactose of dark-grown cells, and 80% of that of light-grown cells. Molar ratios of monogalactosyl to digalactosyl compounds ranged from 2 to 3. The results show that galactosyl diglycerides, stored in large amount in light-grown cells, persist in small amount in the dark-grown cells. Fatty acids in both the monogalactosyl and the digalactosyl diglycerides were mainly of the 16- and 18-carbon varieties, with high proportions of trienes. The monogalactosyl diglycerides were rich in hexadecatetraenoic acid. Strictly photobiotic cells had twice as much hexadecadienoic and hexadecatetraenoic acids in their monogalactosyl diglycerides, and three times as much hexadecadienoic and octadecadienoic acids in their digalactosyl diglycerides as did illuminated cells grown in a complete medium. Dark-grown (obligate) heterotrophs contained galactosyl diglycerides with high percentages of monoenes. Great compositional variations in the galactosyl diglycerides are thus induced by light and also by nonlipid exogenous metabolites.     

Changes in the composition of membrane lipids in relation to differentiation in Aegle marmelos callus cultures

Changes in fatty acid, phospholipid and galactolipid contents during cellular and organ differentiation in Aegle marmelos have been described. Decrease in phosphatidylinositol content and presence of 3-trans-hexadecenoic acid in phosphatidylglycerol were related to greening and shoot buds differentiation. The galactolipids level, the monogalactosyl diglyceride/digalactosyl diglyceride ratio and the linolenic acid level (mainly in monogalactosyl diglyceride) increased with the degree of differentiation, indicating the possible biogenesis of functional chloroplasts.Abbreviations 2,4-D 2,4 dichlorophenoxyacetic acid - BA benzylaminopurine - DW dry weight - FW fresh weight - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PG phosphatidylglycerol - PS phosphatidyl serine - MGDG monogalactosyl diglyceride - DGDG digalactosyl diglyceride - 16:0 palmatic acid - 18:0 stearic acid - 18:1 oleic acid - 18:2 linoleic acid - 18:3 linolenic acid - trans-16:1 3-trans-hexadecenoic acid     

Biosynthesis of monogalactosyl diglyceride by chloroplasts from spinacia oleracea and from some gramineae

Synthetic diglycerides which differed in unsaturation of fatty acids gave the same incorporation of [¹⁴C]galactose from UDP-[¹⁴C]galactose when added to acetone powders of spinach chloroplasts up to about 0·6 mg diglyceride/20 mg acetone powder. Diolein and the endogenous diglyceride isolated from the acetone extract of chloroplasts stimulated galactolipid biosynthesis to a similar extent. With all diglycerides used, monogalactosyl diglyceride was the main product with little accompanying synthesis of digalactosyl diglyceride. The radioactivity in the monogalactosyl diglyceride synthesized from UDP-[¹⁴C]galactose by whole chloroplasts was distributed widely among the monogalactosyl diglycerides with different fatty acid composition. It is concluded that the enzyme which catalyses the transfer of galactose from UDP-galactose to diglyceride is not specific for polyunsaturated diglycerides and that the polyunsaturated monogalactosyl diglycerides arise either by desaturation of the fatty acyl residues after monogalactolipid synthesis or by transacylation. Acetone powders of chloroplasts prepared from several Gramineae did not exhibit transferase activity although whole chloroplasts were active.     

Changes in Chloroplast Lipids during the Development of Photosynthetic Activity in Barley Etio-Chloroplasts

The content of monogalactosyl diglyceride, digalactosyl diglyceride, sulfoquinovosyl diglyceride and phosphatidyl glycerol of gel-filtrated etio-chloroplasts isolated from greening barley seedlings was determined. The development of photosynthetic electron transport, measured as anthraquinone autooxidation, was simultaneously determined with an oxygen electrode. During the first hour of irradiation of the etiolated seedlings the lipid content of the plastids decreased rapidly. The decrease is interpreted as a chlorophyll sensitized photooxidation of the fatty acids of the diglycerides. With artificial electron donors an oxygen uptake was detected after 10 min of greening. With no donors added, a DCMU sensitive oxygen uptake was detected after 2 h. The level of DCMU inhibition increased as the plastid developed and total inhibition was obtained after 5 h. Between 2 and 6 h of greening the lipid content of the plastids stayed constant. During this greening period there was a correlation between the appearance of a DCMU sensitive electron transport and the accumulation of the trans-3-hexadecenoic acid of phosphatidyl glycerol. The trans-3-hexadecenoic acid was present already in the dark-grown seedlings but an increase in content did not occur until after 3 h. The lipid content increased after 6 h of greening. This increase coincided well in time with the formation of grana. The fatty acid composition of the individual lipids, with the exception of phosphatidyl glycerol, and the monogalactosyl diglyceride to digalactosyl diglyceride ratios did not change fundamentally during the greening.     

Biosynthesis of galactolipids by enzyme preparations from spinach leaves

The pH optimum for galactolipid synthesis from UDP-galactose by spinach chloroplasts is 7.2 in Tris-HCl or phosphate buffer. The products include sterol glycosides, trigalactosyl diglyceride (tentatively identified), digalactosyl diglyceride, and monogalactosyl diglyceride in increasing order of quantity. The proportion of monogalactosyl diglyceride decreases and that of digalactosyl diglyceride increases as the pH is lowered. The galactolipid synthesis is quite resistant to elevated temperature; maximal incorporation of galactose from UDP-galactose was observed at 45 degrees C. The proportion of monogalactosyl diglyceride was greater at the higher temperatures. As much as 40% of the galactolipid-synthesizing capability of a spinach leaf homogenate is not sedimented by centrifugation for 60 min at 100,000 g. An acetone powder of spinach chloroplasts contains enzymes which catalyze galactolipid synthesis. This preparation is dependent on added diglycerides in order to make galactolipid, whereas the chloroplast preparation is not dependent on added diglycerides. Molecular species of diglycerides were compared as requirements for galactolipid synthesis. The requirement was satisfied best by the diglycerides of highest unsaturation. Methylation of the free hydroxyl of the diglyceride eliminated the effectiveness.     

Lipids of Chlamydomonas reinhardi under different growth conditions

Photo-, mixo- and heterotrophically grown cultures of Chlamydomonas reinhardi (wild type ss and 2 streptomycin-resistant mutants sr₃ and sr₃₅) have been analyzed for lipids and fatty acids. Ether-soluble lipids, chlorophyll, monogalactosyl diglyceride, digalactosyl diglyceride, sulfolipid, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl glycerol and the relative amounts of fatty acids in total and individual lipids have been determined. The lipid and fatty acid compositions are very similar in the 3 strains and are not affected by the mutations. Fatty acids belong exclusively to the C₁₆ and C₁₈ series, 16:0, 16:4, 18:1, 18:2, 18:3 (6,9,12) and 18:3 (9,12,15) comprising about 90% of the total. 18:3 (6,9,12) is concentrated in phosphatidyl ethanolamine. In streptomycin-bleached sr₃ cells, ether-soluble lipids increase from 7 to 11% of dry weight on greening, mostly due to synthesis of monogalactosyl diglyceride and chlorophyll. Monogalactosyl diglyceride of bleached cells exhibits the same fatty acid pattern before and after greening.     

Separation and Purification of Monogalactosyl and Digalactosyl Diglycerides by Thin-Layer Chromatography

Six kinds of glycolipid of monogalactosyl and digalactosyl diglyceride were separated and purified from the wheat and the natural latex of chilling-tolerant and chilling-sensitive variety by two kind solvent systems and twice one-dimensional thin-layer chromatography. Besides, the compositions of fatty acid of hydrophobic side chain of six kinds of glycolipid were compared. The indices of unsaturation of fatty acid of hydrophobic side chains in the glycolipids of wheat flour, in the glycolipids of natural latex of chilling-tolerant, variety and in the digalactosyl diglycerides, are much bigger than those, respectively, in the glycolipids of natural latexes, in the glycolipids of chilling-sensitive variety and in the monogalactosyl diglycerides.     

用薄层色谱分离提纯单半乳糖和双半乳糖双甘油酯

本文选择两种溶剂体系,用两次单向薄层层析,从小麦抗寒与不抗寒品系天然橡胶胶乳分离提纯出6种单半乳糖和双半乳糖双甘油酯。并比较了它们的疏水侧链的脂肪酸组成。小麦糖脂疏水侧链脂肪酸的不饱和指数远大于天然胶乳糖脂。抗寒品系胶乳糖脂疏水侧链脂肪酸不饱和指数大于不抗寒品系。双半乳糖双甘油酯疏水侧链脂肪酸不饱和指数均大于其单半乳糖糖脂。     

Influence of S-ethyl Dipropylthiocarbamate (EPTC) on the Fatty Acid Composition of Wheat Leaf Galactolipids

Winter wheat (Triticum sativum L. cv. Nisu) was grown in sand which contained 0, 0.25, 0.5 and 1.0 mg S-ethyl dipropylthiocarbamate (EPTC) per kg air dry sand. The galactolipids of leaves of 21-day-old seedlings were isolated by preparative thin layer chromatography. The fatty acids of the mono- and digalactosyl diglycerides were analysed by gas liquid capillary chromatography. The major fatty acids of the wheat leaf galactolipids were palmitic, palmitoleic, stearic, oleic, vaccenic, linoleic and linolenic acids (in the monogalactosyl diglyceride fraction of untreated plants 22.5, 2.4, 3.1, 5.2, 2.5, 51.1 and 1526.6 μg and in the digalactosyl diglyceride fraction 108.8, 2.3, 10.4, 9.9, 8.2, 42.3 and 1120.7 μg/g leaf fresh weight, respectively). Total fatty acid content of the mono- and digalactosyl diglyceride fractions was decreased by 85 and 87%, respectively, at 1 mg EPTC/kg sand, while decrease in the fresh weight of the leaves was 79%. The content of linoleic and linolenic acids/g fresh weight of the leaves was decreased in the monogalactosyl diglyceride fraction by 27 and 43%, respectively, while the content of all other fatty acids was increased. In the digalactosyl diglyceride fraction the content of both linoleic and linolenic acids/g leaf fresh weight was decreased by 55%. The content of palmitic and vaccenic acids was also decreased, whereas the content of other fatty acids remained at the level of the untreated samples. The general quality of the fatty acids in the mono- and digalactosyl diglyceride fractions was altered slightly by EPTC.     

Polygalactolipids in Spinach Chloroplast

Two polygalactolipids, designated as components A and B, were isolated from spinach chloroplasts and were also obtained from glycolipid products synthesized with chloroplast enzymes using uridine diphosphate galactose as a galactose donor. These lipids were purified by column and thin layer chromatography. Chemical analysis of component A indicates that the lipid is trigalactosyl diglyceride, whereas component B behaves like tetragalactosyl diglyceride on a thin layer plate. The major fatty acid in trigalactosyl diglyceride was alpha-linolenic acid. Relative amount (molar ratio) of galactolipids in spinach chloroplasts was monogalactosyl diglyceride:digalactosyl diglyceride:trigalactosyl diglyceride:(tetragalactosyl diglyceride) = 60:30:5:1.     

Degradation of monogalactosyl diglyceride and diagalactosyl diglyceride by sheep pancreatic enzymes

1. Saline extract of sheep pancreas acetone-dried powder was shown to catalyse acyl ester hydrolysis of spinach leaf galactosyl diglycerides and also galactosylglucosyl diglyceride of Lactobacillus casei. 2. Sodium deoxycholate stimulated the enzyme activity. Ca(2+) had no effect on the hydrolysis of monogalactosyl diglyceride, but it enhanced that of digalactosyl diglyceride. When added together, there was considerably less activity with both the substrates. 3. Optimal hydrolysis was observed at pH7.2. 4. The initial point of hydrolysis was at position-1, leading to the formation of monogalactosyl monoglyceride and digalactosyl monoglyceride. Further hydrolysis to the corresponding galactosylglycerols and later to galactose and glycerol was also observed, indicating the presence of alpha- and beta-galactosidases in the enzyme preparation. 5. Formation of monogalactosyl diglyceride from digalactosyl diglyceride by the action of alpha-galactosidase was noted. 6. Monogalactosyl diglyceride was also hydrolysed by beta-galactosidase to a limited extent, giving rise to diacylglycerol and galactose. 7. Attempts at purification of monogalactosyl diglyceride acyl hydrolase by using protamine sulphate treatment, Sephadex G-100 filtration and DEAE-cellulose chromatography gave a partially purified enzyme which showed 9- and 81-fold higher specific activity towards monogalactosyl diglyceride and digalactosyl diglyceride respectively. This still showed acyl ester hydrolysis activity towards methyl oleate, phosphatidylcholine and triacylglycerol. 8. When sheep, rat and guinea-pig tissues were compared, guinea-pig tissues showed the highest activity towards both monogalactosyl diglyceride and digalactosyl diglyceride. In all the species pancreas showed higher activity than intestine.     

The fatty acid composition of fern lipids

Fatty acid compositions of the lipids isolated from the pinnae of four fern species show that they differ from those of the lipids in leaves of higher plants in having C-20 polyunsaturated acids, mainly arachidonic acid. As in higher plants, the ω-3 polyunsaturated acids are concentrated in the monogalactosyl diglycerides. Variations are found both in the fatty acid compositions and in the monogalactosyl/digalactosyl diglyceride ratio during the growing season.     

Lipid composition of chloroplasts isolated by aqueous and nonaqueous techniques

Chloroplasts isolated from tobacco leaves in 0.5 M sucrose solution (the 1000 g pellet) contained 83% of the total cellular monogalactosyl diglyceride, 88% of the digalactosyl diglyceride, 76% of the sulfolipid, and 74% of the phosphatidyl glycerol. Phosphatidyl inositol was concentrated in the 15,000 g pellet. Phosphatidyl choline and phosphatidyl ethanolamine were concentrated in the 15,000 g supernatant fraction. Chloroplasts isolated from tobacco leaves by a nonaqueous technique in hexane-carbon tetrachloride show a glycerolipid composition similar to that found in chloroplasts isolated in the aqueous system, even though some lipid, particularly monogalactosyl diglyceride, is extracted by the organic solvent during the process.     

Lipid Composition of Some Species of Arthrobacter

The lipids from Arthrobacter crystallopoietes, A. pascens, and A. globiformis were investigated. Each strain contained three glycolipids, a monogalactosyl diglyceride, a digalactosyl diglyceride, and a dimannosyl diglyceride, and traces of triand tetraglycosyl diglycerides. The phospholipids in all three strains consisted of bisphosphatidylglycerol, phosphatidylglycerol, and phosphatidylmyoinositol. No evidence could be obtained for the occurrence of mannophosphoinositides. Analysis of the fatty acids by gas-liquid chromatography showed that they are predominantly C_15:0anteiso and C_17:0anteiso compounds. No significant differences were observed in the composition of lipids extracted from homogeneous cell preparations of the rod and sphere forms of A. crystallopoietes.     

Lipid biosynthesis in relation to chloroplast development in barley

During greening of detached leaves from dark-grown barley seedlings, the linolenic acid content of the lipids increases in the early stages of the formation of the chloroplast lamellar system. Primarily the fraction containing monogalactosyl diglyceride is enriched with linolenic acid. Incorporation of (14)C-labeled acetate into the leaf lipids of detached whole leaves is low, but increases 10- to 20-fold during greening. Increasing percentages of label appear in linolenic acid during the first 15 hr of greening, whereafter they remain constant. A constant, relatively high amount of acetate is incorporated into lipids when slices of leaves at various stages of greening are incubated by submersion in acetate solution, a treatment that blocks further chlorophyll synthesis during incubation. At the initial greening stages 75% of the label is channeled into steroids and other unsaponifiable lipids, but in advanced stages of chloroplast development 75% of the incorporated acetate is built into phospho-, sulfo- and galacto-lipids, and only 25% is channeled into unsaponifiable lipids. Experimental variation of the physiological conditions of the tissue during incubation resulted in differences in the amount of label found in the various phospho- and galacto-lipids. The amounts of labeling of the individual fatty acids in the lipid classes studied differ markedly and could be changed by varying the conditions of incubation. Labeling of linolenic acid was found to be highest in the monogalactosyl diglyceride fraction at all stages of greening.     

Manipulation of galactolipid Fatty Acid composition with substituted pyridazinones

The fatty acid composition of the major lipids of the chloroplast membranes, the mono- and digalactosyl diglycerides, can be definably altered with various substituted pyridazinones. Galactolipid fatty acid composition of wheat (Triticum aestivum L.) can be altered so that there is a decrease in linolenic acid accompanied by an increase in linoleic acid without a shift in the relative proportion of saturated to unsaturated fatty acids; the fatty acid composition can be shifted toward a higher proportion of saturated fatty acids; or the fatty acid composition of the monogalactosyl diglycerides can be altered in preference to the digalactosyl diglycerides. Also, the light-mediated parallel accumulation of chlorophyll and linolenic acid can be separated with a substituted pyridazinone. The substituted pyridazinones may be useful tools in clarifying the role the galactolipids and their component fatty acids play in the structure and function of chloroplast membranes in higher plants.     

Changes in Glycolipid and Phospholipid Compositions in Cotyledons of Germinating Soybeans

This investigation was conducted to observe changes in the compositions of fatty acids, glycolipids (GL) and phospholipids (PL) in cotyledons of soybean seeds which were germinated either in the dark or the light at 28°C for 8 days. The patterns of changes in lipid composition depended on the germinating conditions tested. In general, non-polar lipids were metabolized at a faster rate than polar lipids. Changes in lipid contents in cotyledons were also observed more clearly with the polar lipids than with the non-polar ones, especially in the light-grown seedlings. The major component of lipid, GL in chloroplasts, appeared rapidly at an earlier stage in the cotyledons of light-grown seedlings. During germination of soybean seeds, acyl sterylglucoside in cotyledons decreased rapidly, but monogalactosyl diglyceride and digalactosyl diglyceride (DGD) increased in the light-grown seedlings, whereas sterylglucoside and DGD increased in the dark-grown seedlings.

The major PL present immediately after immersion were phosphatidyl ethanolamine (PE), phosphatidyl choline (PC) and phosphatidyl inositol (PI). During germination under both conditions, light and dark, PE in cotyledons decreased with PC or PI, while phosphatidic acid increased rapidly, and phosphatidyl glycerol and diphosphatidyl glycerol also increased slightly. These changes in glycolipid and phospholipid compositions during germination seem to occur from the formation of photosynthetic tissues and the metabolic interconversion of phospholipids.     

Effect of Storage in Darkness and in Light on the Content of Membrane Lipids of Potato Tubers

The lipid composition of tubers from the potato varieties Bintje and Desirée was investigated during storage. Storage in total dark ness after harvest gave only small changes in the amounts of triglycerides. monogalactosyl diglycerides and digalactosyl digtycerides. Storage in light resulted in changes in these lipids and in their fatty acid composition. The absolute amount and the relative content of linolenic acid in the galactolipids increased. A simultaneous and equivalent decrease in the percentage of linoleic acid took place without any marked percentage changes in the other major fatty acids. The light induced changes of the lipids, which occur simultaneously with greening of the tuber, are discussed and related to the development of thylakoid membrane systems in the plastids.     

Galactolipids and phospholipids of orange peel and juice chromoplasts

Chromoplasts from yellow orange (Citrus sinensis) fruit peel contain monogalactosyl diglycerides (MGDG), digalactosyl diglycerides (DGDG) and phosphatidyl glycerol (PG) in amounts similar to those found in chloroplasts from green fruit peel. Juice chromoplasts contain relatively little MGDG and no DGDG with high levels of phosphatidyl choline and phosphatidyl ethanolamine but no PG.     

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