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The chemical structure of the free lipid A isolated from Mesorhizobium huakuii IFO 15243T was elucidated. Lipid A is a mixture of at least six species of molecules whose structures differ both in the phosphorylation of sugar backbone and in fatty acylation. The backbone consists of a β (1′→6) linked 2,3-diamino-2,3-dideoxyglucose (DAG) disaccharide that is partly substituted by phosphate at position 4′. The aglycon of the DAG-disaccharide has been identified as α- d-galacturonic acid. All lipid A species carry four amide-linked 3-hydroxyl fatty residues. Two of them have short hydrocarbon chains (i.e. 3-OH- i-13:0) while the other two have longer ones (i.e. 3-OH-20:0). Distribution of 3-hydroxyl fatty acids between the reducing and nonreducing DAG is symmetrical. The nonpolar as well as (ω-1) hydroxyl long chain fatty acids are components of acyloxyacyl moieties. Two acyloxyacyl residues occur exclusively in the nonreducing moiety of the sugar backbone but their distribution has not been established yet. The distal DAG amide-bound fatty acid hydroxyls are not stoichiometrically substituted by ester-linked acyl components. [ABSTRACT FROM AUTHOR]

Unsaturated free fatty acids and adenosine operate two neuromodulatory systems with opposite effects on neuronal function. Here, we tested if fatty acids controlled inhibitory adenosine A1 receptors. Arachidonate (AA, 10 µm) decreased the Bmax of an A1 receptor agonist, (R)-[3H]phenylisopropyladenosine (PIA; from 812 to 267 fmol·mg-1 protein), and antagonist, [3H]1,3-dipropyl-8-cyclopentylxanthine (DPCPX; from 994 to 311 fmol·mg-1 protein) and decreased the Kd of [3H]PIA (from 1.20 to 0.57 nm) binding to brain membranes of young adult rats (2 months old), these effects being mimicked by other cis but not trans unsaturated or saturated fatty acids. AA (10 µm) increased the potency of the A1 receptor agonist, 2-chloroadenosine to inhibit hippocampal synaptic transmission in young adult rats (EC50 decreased from 337 to 237 nm), which may constitute a safety feedback mechanism to control AA-induced neurotoxicity. Upon aging, there were increased free fatty acid levels and a concomitant decreased density of A1 receptors. This was more marked in hippocampal nerve terminals of aged rats (24 months old) and may be the determinant factor contributing to the lower potency of 2-choloroadenosine in aged rats (EC50 = 955 nm), in spite of the decreased Kd of PIA binding upon aging. The effects of AA on A1 receptor binding were attenuated upon aging, AA being devoid of effects in aged rats. Accordingly, AA (10 µm) failed to modify the potency of 2-choloroadenosine in aged rats (EC50 = 997 nm). However, albumin, which quenches free fatty acids, increased A1 receptor density by 65% and 2-chloroadenosine potency (EC50 = 703 nm) in aged rats, suggesting that the increased fatty acids levels in aged rats may contribute to the decreased potency of A1 receptor agonists in aged rats. Also, the observed saturation of the control by AA of A1 receptors may contribute to the decreased adaptability of neuromodulation to different firing conditions in aged rats. [ABSTRACT FROM AUTHOR]

When P388D1 cells are incubated in media containing 10 μM [3H]arachidonic acid (Δ4Ach), the label is rapidly incorporated into phospholipids and triacylglycerol. However, incorporation of [3H]Δ4Ach into phospholipids clearly precedes incorporation into triacylglycerol, indicating that the phospholipid pool constitutes the primary metabolic fate of the Δ4Ach via a remodelling pathway. In contrast, [3H]Δ4Ach is incorporated into triacylglycero] almost exclusively via de novo synthesis, as evidenced by studies using propranolol, a phosphatidate phosphohydrolase inhibitor. This compound induced a time-dependent and concentration-dependent increase in the levels of [3H]Δ4Ach-containing phosphatidate that is directly correlated with a decrease in the levels of [3H]4Ach-containing triacylglycerol. In addition, no change in the levels of [3H]Δ4Ach-containing diacylglycerol and monoacylglycerol were apparent along the time course of fatty acid incorporation into triacylglycerol. However, a sharp and transient accumulation of cell-associated free [3H]Δ4Ach was detected shortly after exposure of the cells to the radioactive fatty acid. Collectively, the results reported herein suggest that free Δ4Ach availability determines the patterns of incorporation and distribution of this fatty acid among the various lipid classes of P388D1 cells. [ABSTRACT FROM AUTHOR]

The major unidentified polar lipid (compound X), recently demonstrated in the cell membrane of Mycoplasma fermentans,was purified by preparative silicic acid column chromatography. Chemical analyses of acid-hydrolyzed compound X revealed that, in addition to fatty acids, it contains glycerol, choline and. phosphate in a molar, ratio of approximately 1:1:2, and an amino acid that has a retention time similar to that of homoserine. The methylated fatty acid fraction of compound X was subjected to gas-liquid chromatography and revealed methyl palmitate and methyl stearate in a 4.6:1 molar ratio. The structure of compound X was further analyzed by combining mass spectrometry, 31P-NMR and ¹H-NMR. The positive and negative fast atom bombardment spectra showed a major component of Mr 1048 and a minor component of Mr 1076. Two different phosphate groups were identified in each of the components by 31P-NMR. Fast atom bombardment, tandem mass spectrometry, negative and positive chemical ionization mass spectrometry together with mass spectra analyses of the water-soluble and ether-soluble products obtained by methanolysis has shown that, in addition to palmitic and stearic acid residues, the presence of glycerol, ribitol, cholinephosphate and homoserinephosphate residues. It is suggested that the apparent structure of compound X is either a phosphatidylcholine attached via a phosphotriester bond to a ribitolphosphohomoserine moiety or a phosphatidylhomoserine attached via a phosphotriester bond to a ribitolphosphocholine moiety. The major molecular species .is the dipalmitoylderivative (Mr 1048), whereas the minor molecular species is a stearoyl palmitoyl derivative (Mr 1076). [ABSTRACT FROM AUTHOR]

The effect of bezafibrate on cytosolic fatty-acid-binding-protein (FABPc) production along the small intestine has been investigated in mice. This drug increased the intestinal fatty-acid-binding-protein (I-FABPc) and liver fatty-acid-binding-protein (L-FABPc) mRNA levels in the duodenum. The extents of induction in the duodenum and in the liver are similar. However, the degree of stimulation gradually decreases along the length of the gut, no effect being found in the ileum. An efficient absorption of this drug as early as the proximal part of the small intestine may explain this phenomenon. The L-FABPc gene is silent in terminal ileum of mice, but a direct infusion of bezafibrate into the ileum switches it on. We used this original model to follow the time course of induction of the L-FABPc gene by bezafibrate. L-FABPc mRNA was first detected 4 h after fibrate infusion, reached a maximum level at 16 h and subsequently decreased at 24 h. This induction was totally blocked by cycloheximide. Sunflower oil also caused small increases in the L-FABPc mRNA levels. The transcriptional origin of the induction triggered both by bezafibrate and sunflower oil was demonstrated by run-on assays. These data indicate that (a) the transcription of the L-FABPc gene is induced by bezafibrate via de novo protein synthesis and (b) components of sunflower oil can transcriptionally activate the L-FABPc gene. Our results also demonstrate that the mouse terminal ileum is a useful system for studying the regulation of L-FABPc gene expression both in vivo and in vitro. [ABSTRACT FROM AUTHOR]

The small, cell-wall-less prokaryote Acholeplasma laidlawii strain A-EF22 could grow with membrane lipids having an average acyI chain length &Cmacr;n varying over 14.5—almost 20 carbons by exogenous supplementation with selected fatty acids. For 16 < &Cmacr;n < 18, the cells grew with lipids containing 100% (mol/100 mol) monounsaturated acyI chains, whereas for &Cmacr;n < 16 and &Cmacr;n < 18, cell growth only occurred with gradually lower fractions of unsaturated chains. &Cmacr;n was actively increased and decreased by chain elongation or de novo fatty acid synthesis upon incorporation of short-chain and long-chain fatty acids, respectively. The membrane lipid composition was strongly affected by the acyI chain length and unsaturation, and the metabolic responses are readily explained as a regulation mechanism based on the established phase equilibria of the individual lipids in the A. laidlawii membrane. Monoglucosyldiacylglycerol (Glc-acyI2-Gro) was the dominating lipid with short chains but the fraction of this lipid decreased with increasing Cn, correlating with the decreasing lamellar to nonlamellar phase transition temperatures for this lipid. The fractions of diglucosyldiacylglycerol (Glc2-acyI2Gro) and phosphatidylglycerol (PtdGro), forming lamellar phases only, increased with increasing C¯n over the entire chain-length interval. A weaker correlation was usually observed between the relative amount of a lipid and the extent of chain unsaturation; however, the fractions of Glc2-acyI2Gro and PtdGro increased clearly with an increasing degree of unsaturation. Moreover, the synthesis of the nonbilayer-forming lipids acyI2Gro and monoacyl-Glc-acyI2Gro was strongly stimulated by a high degree of chain saturation. Concomitantly, the phase equilibria of Glc-acyI2Gro are shifted towards lamellar phases at the growth temperature. The fraction of the three potentially nonbilayer-forming lipids varied over 10–80% (mol/100 mol) total lipids as a function of the acyI chain composition. The combined molar fractions of the three phospholipids increased strongly with chain unsaturation. However, the fraction of phosphate moieties in the different lipids was constant over the entire chain-length interval. It is concluded that the regulation of the membrane lipid composition aims at maintaining similar phase equilibria and surface charge densities of the lipid bilayer. The size of A. laidlawii cells was changed in a systematic manner and correlated qualitatively with the packing properties of the lipids. Cell diameters were increased by an increase in acyI chain length and saturation, and was affected by additives such an n-dodecane and acyI2Gro. [ABSTRACT FROM AUTHOR]

To investigate the importance of factors influencing substrate availability for triacylglycerol biosynthesis on lipoprotein metabolism, the effects of two opposite-acting sulphur-substituted fatty acid analogues, tetradecylthioacetic acid and tetradecylthiopropionic acid were studied. Administration of tetradecylthioacetic acid to rats resulted in a reduction of plasma levels of triacylglycerols (44%) and cholesterol (26%). This was accompanied by a reduction in very-low-density lipoprotein (VLDL) triacylglycerols (48 %), VLDL cholesterol (36 %), low-density lipoprotein (LDL) cholesterol (36 %) and high-density lipoprotein (HDL) triacylglycerols (50%), whereas HDL cholesterol levels did not change. Subsequently, the HDL/LDL-cholesterol ratio increased by 40%. The cholesterol-lowering effect was accompanied by a reduction in hydroxymethylglutaryl CoA (HMG-CoA) reductase activity (37%). Both mitochondrial and peroxisomal fatty acid oxidation increased (1.7-fold and 5.3-fold, respectively). Furthermore, there was a significant negative correlation between plasma triacylglycerols and mitochondrial fatty acid oxidation. Hepatic triacylglycerol synthesis was retarded, as indicated by a decrease in VLDL triacylglycerol secretion (40%.), and by a reduced liver triacylglycerol content (29%). The activities of lipoprotein lipase and hepatic lipase m post-heparin plasma were not affected. Microsomal and cytosolic phosphatidate phosphohydrolase activities were inhibited (28% and 70%, respectively). Hepatic malonyl-CoA levels decreased by 29% and the total activity of acetyl-CoA carboxylase was reduced (23%). In hepatocytes treated with tetradecylthioacetic acid, mitochondrial fatty acid oxidation increased markedly (100%) and triacylglycerol secretion was reduced (40%). In tetradecylthiopropionic-acid-treated rats, a significant increase in both plasma and VLDL triacylglycerols was found (46% and 72 %, respectively) but VLDL triacylglycerol secretion was unaffected. However, no effect on either plasma or lipoprotein cholesterol levels was seen. Mitochondrial fatty acid oxidation was decreased by 50% and hepatic triacylglycerol levels increased by 33 %. In hepatocytes exposed to tetradecylthiopropionic acid, triacylglycerol synthesis increased (100%) while triacylglycerol secretion and fatty acid oxidation remained unaltered. The results illustrate that lipoprotein triacylglycerol levels can be modulated by changes in the availability of fatty acid substrate for triacylglycerol biosynthesis, mainly by affecting mitochondrial fatty acid oxidation. In addition, we demonstrate that suppression, of rat hepatic HMG-CoA reductase activity during treatment with tetradecylthioacetic acid may contribute to a cholesterol-lowering effect. [ABSTRACT FROM AUTHOR]

Lipoprotein lipase (LPL) was rapidly inactivated by low concentrations of active-site inhibitor tetrahydrolipstatin (THL). The presence of amphiphils (e.g. long-chain fatty acids) or of lipid/water interfaces (lipid emulsions) was required for inhibition to occur. Apolipoprotein CII increased the maximal inactivation rate constant by 1.8-fold in the presence of an emulsion of long-chain triacylglycerols, but had no effect in the presence of an emulsion of tributyrylglycerol. The fully inhibited enzyme had a ratio of THL/LPL of nearly 2, indicating that both subunits of the LPL homo-dimer bound THL. The THL-LPL complex was stable below pH 7.5. At higher pH reactivation occurred indicating that THL was slowly turned over by the enzyme. The apparent reactivation rate constant was increased about threefold by the presence of lipid/water interfaces. Sucrose density gradient centrifugation revealed that THL induces tetramerisation of LPL. This aggregation was reversible was reversible on reactivation of the inhibited enzyme. Binding to heparin was not affected by THL. In contrast, binding to lipid droplets and to lipoproteins was increased, indicating exposure of hydrophobic regions in the inhibited LPL. It is suggested that THL induces local conformational changes in LPL, which may involve opening of the putative surface lid structure which covers the active-site. [ABSTRACT FROM AUTHOR]

Photosystem II membrane fractions from dark-adapted mesophyll chloroplasts of maize were solubilized in different concentrations of dodecyl β-D-maltoside. Chlorophyll-binding proteins from photosystem Il were isolated either by ultracentrifugation on a sucrose gradient, or by fiat bed isoelectric focusing and identified by gel electrophoresis analysis for their polypeptide composition. Lipid and fatty acid compositions were determined in complexes prepared by both methods and also in purified light-harvesting complex II, in minor chlorophyll a/b binding complexes 29, 26, 24, in photosystem II antennae (chlorophyll-protein complexes 43. 47) and in the photosystem II reaction centers chlorophyll-protein complexes. Comparative analysis of the results suggests that a true heterogeneity exists in the lipid class distribution among the different chlorophyll-protein complexes in this region of the photosynthetic membrane. Photosystem Il core fractions prepared either by ultra-centrifugation on a sucrose gradient or by isoelectric focusing were found significantly enriched in monogalactosyldiacylglycerol; fractionation of the photosystem-II core in its components showed that it was the chlorophyll-protein complexes 43 and 47 which were mainly responsible for this enrichment. One of them, the chlorophyll-protein complex 47, was found containing monogalactosyldiacylglycerol and having a very high level of saturated fatty acids. The minor chlorophyll a/b binding linkers (chlorophyll-protein complexes 24, 26 and 29) retain a largely higher amount of lipids than all other complexes and especially of highly unsaturated galactolipids. Concerning the main light-harvesting antenna (LHCII), it is demonstrated that phosphatidylglycerol is strongly linked to the complex if it cannot be detached at high detergent concentration. while many galactolipids (which nevertheless represent the major lipid classes) are lost. This main light-harvesting complex has been fractionated into several families by isoelectric focusing showing a marked difference in lipid and polypeptide composition. A spectacular increase in the phosphatidylglycerol content was observed in the fraction migrating near the anode and enriched in a 26-kDa polypeptide; but this result is difficult to interpret in physiological terms as it was shown that phosphatidylglycerol alone, because of its negative charge, also migrates toward the anode in isoelectric focusing. [ABSTRACT FROM AUTHOR]

The phase structure of isolated bacterial lipid A, the lipid anchor of the lipopolysaccharides of the outer membrane of Gram-negative bacteria, has been investigated by neutron small-angle scattering. The shape of the scattering curves obtained at different H2O/²-H2O ratios revealed a lamellar organisation of the lipid A at neutral pH both above and below its main phase temperature (approximately 40 -45'C). Analysis of the scattering curves and interpretation of the corresponding thickness distance distribution functions of the lamellar aggregates led to a model in which the lipid A molecules form a bilayer of about 5 nm in thickness. This value for the thickness of the bilayer, as well as the neutron-scattering density profile across the bilayer, can be explained by a molecular model which shows interdigitation of the fatty acid chains of the lipid A. [ABSTRACT FROM AUTHOR]

The acyl-carrier protein (ACP) in Neurospora crassa mitochondria [Brody, S. & Mikolajczyk, S. (1988) Eur. J. Biochem. 173, 353–359] mediated a cerulenin-sensitive, de novo fatty acid synthesis independent of the fatty acid synthetase complex present in the cytoplasm. Incubation of mitochondria with 12-14C]malonate labeled only the ACP as indicated by autoradiography after SDS/PAGE. Under these in vitro conditions ATP was required for the initial acyl-ACP formation, but further elongation required either magnesium or the direct addition of NADPH. Labeled hexanoic (6:0) and caprylic (8:0) acids were detected as intermediates in the pathway, as well as hydroxymyristic acid. All of the intermediates, and the eventual product of the reaction, myristic acid (14:0), were released from the ACP by alkaline treatment. Pulse-chase experiments demonstrated the incorporation on to, and release of label from, the ACP. In vivo labeling of ACP with [2-14C]malonate was also detected and the label was in the form of hydroxymyristic acid. This newly discovered pathway is discussed from the standpoint of its possible role in providing acyl chains for mitochondrial lipids. [ABSTRACT FROM AUTHOR]

Leaves of Glechoma hederacea L. and other Labiatae contain (9S,10E,12Z,15Z)-9-hydroxy-10,12,15octadecatrienoic acid, (10E,12Z,15Z)-9-oxo-10,12,15-octadecatrienoic acid, (9S,10E,12Z)-9-hydroxy-10,12octadecadienoic acid and (10E,12Z)-9-oxo-10,12-octadecadienoic acid in a ratio of 71/14/12/3 (by mass), predominantly esterified in the membrane ester lipids. The leaves contain the highest level of these products, whereas only small amounts were found in the stalk and the roots. The chemical structures of these compounds were established by ultraviolet and infrared spectroscopy, by co-chromatography with authentic standards on various types of HPLC columns including chiral-phase HPLC and gas chromatography/mass spectrometry. The stereochemical specificity indicates the enzymatic origin of the products, most probably via a lipoxygenase reaction. Freshly harvested specimens of G. hederacea L. contain only small amounts of hydroxy-polyenoic fatty acids. Air-drying causes a strong increase in the content of free and esterified (9S,10E,12Z,15Z)-9-hydroxy10,12,15-octadecatrienoic acid. Up to 80% of the hydroxy fatty acids of the total lipid extracts were esterified in the cellular lipids. The data presented indicate that lipoxygenase products occur in the cellular ester lipids of G. hederacea L. and other Labiatae. The results are discussed in the light of a possible involvement of the lipoxygenase pathway in the natural senescence of leaves. [ABSTRACT FROM AUTHOR]

Ornithine-containing lipids purified by thin-layer chromatography were found to represent 2-15% of the total extractable cellular lipids in two or three strains each of four Pseudomonas species: P. aeruginosa, P. fluorescens, P. stutzeri and P. cepacia. The structures of the ornithine-containing lipids were elucidated by chemical analysis, thin-layer chromatography, gas-liquid chromatography, gas-liquid chromatography/mass spectrometry (electron impact or secondary ion) and infrared absorption spectroscopy. At least six molecular species of ornithine-containing lipids were present in common in all of the preparations of the four Pseudomonas species. The structure which was the most abundantly in P. fluorescens (about 60% of the total amount of the ornithinecontaining hpid) was 3-hydroxyhexadecanoic acid amide-linked to ornithine and esterified to hexadecanoic acid. In addition to this structure, 3-hydroxyoctadecenoic acid amide-linked to ornithine and esterified to hexadecanoic acid was a dominant structure in the ornithine-containing lipids of P. aeruginosa, P. stutzeri or P. cepacia. In P. cepacia, another ornithine-containing lipids with a terminal polar fatty acid, 3-hydroxyhexadecanoic acid amidelinked to ornithine and esterified to 2-hydroxynonadecacyclopropanoic acid or 2-hydroxyoctadecenoic acid, was found; its content, which represented 8 - 11% of the total extractable cellular lipids, was higher than that of the ornithine-containing lipids with a terminal nonpolar fatty acid. These ornithine-containing lipids exhibited hemagglutinating activity. Additionally, it was very interesting that hydroxy fatty acids included in the ornithinecontaining lipids were not found in the phospholipids which represented more than 80% of the total extractable cellular lipids. [ABSTRACT FROM AUTHOR]

Replacement of the normal culture liquid to a nitrate-free medium resulted in an immediate drop in the ratio of protein to lipid in isolated cell envelopes of Anacystis nidulans cells. The relative fluidity of the envelope membranes or liposomes, made from the extracted lipids of the envelope, was estimated by measuring the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. A thermotrophic phase transition of lipids within the cytoplasmic membrane of intact cells was also revealed by detecting the temperature-dependent absorption changes in the proportion of zeaxanthin at 390 nm. It became evident that a decrease in the proportion of protein to lipid within the cell envelope was accompanied neither by changes in the microviscosity level, nor by shifting of characteristic temperatures of the liquid-crystalline-to-gel transition of lipids. In parallel with nitrate starvation, however, the proportion of saturated fatty acids of the envelope lipids increased markedly. Accumulation of saturaged, longer-chain (C18) fatty acids at the cost of C16 counterparts upon nitrate deprivation occured in all of the complex lipids. In accordance with these findings, a pronounced decrease in the fluidity was demonstrated for the liposomes prepared from the envelope polar lipids of nitrate-starved cells compared with corresponding control, throughout the temperature range (45-5°C) studied. We propose that the fluidizing effect due to a fall in the ratio of protein to lipid was compensated by a rapidly triggering regulatory process which enables the preservation of the fluidity characteristics at an optimal level within the cell envelope of A. nidulans. [ABSTRACT FROM AUTHOR]

The lipid metabolism in cultured fibroblasts from multisystemic (type 3) lipid storage myopathy (MLSM) and controls has been studied through pulse-chase experiments using radiolabelled oleic acid and acetate precursors. 1. The uptake of radiolabelled oleic acid by MLSM fibroblasts was slightly higher than in controls but did not seem to be the primary defect of the multisystemic lipid storage myopathy. The uptake of radiolabelled acetate was quite similar in MLSM and in control cells. 2. During short-time pulse periods, using either radiolabelled oleic acid or acetate as precursors, we observed no significant difference in lipid composition between MLSM and controls. In contrast, pulse experiments using radiolabelled oleic acid as precursor showed a major accumulation of radiolabelled triacylglycerols in MLSM (around 1000% of controls); no significant increase of other neutral or polar lipids was noticed. A similar triacylglycerol storage was observed by using radiolabelled acetate as precursor, but in this case the difference between MLSM and controls was more pronounced; we also observed in MLSM cells a higher amount of polar lipids which can be due to an increased rate of fatty acid biosynthesis (from radiolabelled acetate). 3. Chase experiments, after pulse by low concentration of exogenous radiolabelled oleic acid or acetate, showed similar features: the biosynthesized triacylglycerols were not at all degraded in MLSM, but on the contrary increased, probably by accumulation of radiolabelled triacylglycerols newly synthesized from radiolabelled fatty acids liberated during the phospholipid turnover. Similarly, the triacylglycerol storage induced by high doses of fatty acids was not degraded in MLSM cells, in contrast to control cells. This suggested that the triacylglycerols synthesized in the presence of low and high levels of fatty acids were accumulated in only one subcellular cytoplasmic compartment without relationship with the Iysosomal compartment, since these cells were not deficient in acid lysosomal lipase. The more probable hypothesis is a deficiency of the cytoplasmic catabolism of triacylglycerols in MLSM cells. [ABSTRACT FROM AUTHOR]

9-(2-Anthryl)-nonanoic acid is a new fluorescent and photoactivable probe, which has been designed for studying the lateral diffusion rate and the lateral distribution of lipids in biological membranes by means of the anthracene photodimerization reaction. It is shown that this anthracene fatty acid is metabolically incorporated into the glycerophospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol) of the eukaryotic Chinese hamster ovary cells in culture. Under our culture conditions (Eagle's minimal essential medium plus delipidized fetal calf serum) this incorporation proceeded with a very good rate (up to 45 mol/100 mol, after two days culture) and could be easily modulated depending on the way the cells were fed with the anthracene fatty acid. It occurred to a similar extent at the sn-1 (55 ± 5%) or at the sn-2 (45 ± 5%) position on the phospholipid glycerol backbone, without any degradation or elongation. No double labeling at the sn-1 and sn-2 positions was detected. Although incorporation of the anthracene fatty acid affected the cell growth rate (generation time of 48 h compared to a generation time of 21 h for control cells) it did not bring about cell mortality. This incorporation took place not only into the phospholipids but also into the triglycerides with, as a consequence, the appearance of strongly fluorescent lipid vesicles inside the cells. It affected the whole cell fatty acid composition by slightly increasing the amount of palmitic acid and markedly decreasing the amount of stearic and oleic acids. [ABSTRACT FROM AUTHOR]

It has previously been demonstrated [Eur. J. Biochem. 124, 191–198 (1982) and 137, 15–22 (1983)] that the lipid A component of Salmnonella and Proteus lipopolysaccharides contains amide-linked (R)-3-acyloxyacyl residues. In the present study lipid A of other gram-negative bacteria was analysed for the presence of amide- bound 3-acyloxyacyl residues. It was found that such residues are constituents of all lipid A tested [Agrobacterium tumefaciens, Chromobacterium violaceum, Pseudomonas aeruginosa, Xanthomonas sinensis, Bacteriodes fragilis, Vibrio cholerae, Fusobacterium nucleatum, Rhodospirillum tenue, Acinetobacter calcoaceticus, and Escherichia coli). Amide-linked (R)-3-acyloxyacyl groups, therefore, represent common and ubiquitous structural elements of bacterial lipid A. The composition of 3-acyloxyacyl groups differed considerably among different bacteria. As amide-bound (R)-3-hydroxy fatty acids straight chain and isobranched acyl groups with 10–17 carbon atoms were identified. The most frequently encountered fatty acids, substituting the 3-hydroxyl group of 3-hydroxy fatty acids, were nonhydroxylated straight chain and isobranched acyl residues with 10–17 carbon atoms as well as (S)-2-hydroxy fatty acids with 12 carbon atoms. In some cases, using laser desorption mass spectrometry, the distribution of 3-acyloxyacyl residues over the two available glucosamine amino groups of the lipid A backbone was investigated. [ABSTRACT FROM AUTHOR]

20 bacterial strains (corresponding to 16 species) were screened for ornithine lipids. Only two species (Thiobacillus A2 and Achromobacter sp.) turned out to contain ornithine lipids (2.71 mmol/100g and 0.38 mmol/100 g bacterial dry weight, respectively). In both ornithine lipids, a 3-hydroxy fatty acid was amide-linked to the α-amino group of ornithine, a normal fatty acid was ester-linked to the 3-hydroxy group of the former. The predominant fatty acids were 18:1(11) and 3-hydroxy-20:1(13) in Thiobacillus A2, 16:0 and 3-hydroxy-18:1(11) in Achromobacter sp. All monounsaturated fatty acids (with one exception) belonged to the (n-7) family. 11, 12-Epoxy octadecanoic acid was identified among the ester-linked fatty acids of Thiobacillus A2. Phosphatidylcholine was the principal phospholipid in both bacterial species. [ABSTRACT FROM AUTHOR]

Interferon-inducing, pyrogenic and proclotting enzyme of horseshoe crab activation activities of chemically synthesized lipid A analogues were investigated and compared with the same activities of a natural lipid A. These analogues are nonphosphorylated, C-1 or C-4′ monophosphorylated and C-1,4′ bisphosphorylated derivatives of β-1,6-linked D-glucosamine disaccharide possessing both ester-bound and amide-bound fatty acid substituents. Fatty acid substituents of the analogues are tetradecanoyl (C14)(R)-3-hydroxyletradecanoyl (C14-OH) or (R)-3-tetradecanoyloxytetradecanoyl [C14-O-(C14)] groups. The biological activities of the samples were assayed after solubilization with triethylamine and complexing with bovine serum albumin. Interferon-inducing activity was exhibited by both the C-1 monophosphorylated compounds examined. Ester-bound and amide-bound fatty acid substituents of these compounds are both C14 or C14 and C14- OH, respectively. Nonphosphorylated, C-4′ monophosphorylated and C-1,4′ bisphosphorylated compounds possessing the same fatty acid substituents as those of the C1 monophosphorylated compounds showed no detectable interferon-inducing activity. C-4′ monophasphorylated compounds possessing C14-OH as ester-bound and C14-OH or C14-O-(C14) as amide-bound fatty acid substituents exhibited interferon-inducing activity, but nonphosphorylated compounds possessing the same fatty acid substituents did not. None or the analogues exhibited significant pyrogenicity nor proclotting enzyme of horseshoe crab activation activity under the conditions employed in this study. [ABSTRACT FROM AUTHOR]

Diacyiglycerol kinase apoprotein was purified from membranes of Ese/wriclila coli K 12. The protein was catalytically inactive, but regained activity upon rccombination with phospholipids, certain neutral lipids, or fatty acids. Activation proceeded with positive cooperativity and was independent of the exact chemical structure, bilayer arrangement or electrical charge oft he lipid. The apoprotein was activated by lysophosphatidylethanola mine but not by lysophosphatidylcholine. 1-Monoolcoylglycerol was an effective activator and substrate at the same time. The fluidity and the polarity of lipids appeared to be generally important for activation. Lipid polarity was estimated by a triacylglycerol/phosphatidylcholine-partitioning procedure. All lipids showing preferential association with tri- acylglycerol failed to activate the kinase apoprotein even in the presence of detergent. It is concluded that a defined hydrophilic/lipophilic balance of the lipid was required for the formation of a functional lipoprotein complex. [ABSTRACT FROM AUTHOR]

The existence of fluid and solid lipid domains in isolated rat-liver plasma membranes was evaluated using the fluorescent fatty acids trans-parinarie and cis-parinaric acid as probe molecules for solid and fluid membrane areas, respectively. The fluorescence probe 1 ,6-diphenyl-l ,3,5-hexatriene indicated that a phase transition was present in the liver plasma membrane between 18 °C and 30°C. At intermediate temperatures, cis-parinaric acid, which partitioned approximately equally into fluid and solid lipid areas, detected two lipid domains: the mole fractions of fluid and solid lipid domains at 24°C were 0.32 and 0.68 while the mole fractions of cis-parinaric acid in each domain were 0.34 and 0.66, respectively. The dissociation constant, aqueous to membrane lipid partition coefficient, and bound to free ratio for trans-parinarie acid were 7.0 ± 0.7 μM. 4.0 ± 0.6 × 106, and 83: 17. respectively. The affinity of the membrane for cis-parinaric acid Was twofold lower than for trails-parinaric acid. The trans-pannaric acid partitioned preferentially into solid lipid. Kpf = 3.30, while the cis-parinaric acid partitioned equally between fluid and solid phases Kpf = 0.92. Thus the data demonstrate the coexistence of fluid and solid domains in rat liver plasma membranes. [ABSTRACT FROM AUTHOR]

The structural properties of isolated purified rat brain synaptosomal membranes, both in the presence and absence of purified active toxin of the Mojave snake Crotalus scutulutus scutulatus, were studied by spin-label electron spin resonance techniques. The spectra from eight different positional isomers of nitroxide-labelled stearic acids, a rigid steroid androstanol, and a spin-labelled phosphatidylcholine intercalated into the synaptosomal membranes were obtained as a function of temperature from 4-40°C. The flexibility gradient (from spin-label order parameters) and polarity profile (from isotropic splitting factors) across the synaptosomal membranes, was characteristic for lipid bilayers. The nitroxide spin-labelled steroid, androstanol, intercalated into the synaptosomal membrane, revealed the abrupt onset of rapid cooperative rotation about the long axis of the molecule at 12°C showing that the lipid molecules are rotating rapidly around their long axes at physiological temperatures, The presence of the Mojave toxin affected the synaptosomal membrane in a complex manner, depending upon the temperature and the position of the nitroxide label on the alkyl chain of the stearic acid probe. Mojave toxin exerted little effect on the flexibility gradient of the synaptosomal membrane at 20°C, a temperature at which the acyl chain labels detected a structural change in the membranes. At temperatures lower than 20°C, the Mojave toxin produced a change in the flexibility gradient of the synaptosomal membrane which indicated an increased disordering in the upper region of the membrane and a concomitant increased ordering of the acyl chains in the deeper regions of the membrane. At temperatures higher than 20°C, the order profile of the synaptosomal membrane was shifted by the presence of the Mojave toxin in a manner which indicated that the outer parts of the membrane were more rigid and the inner regions more fluid, than in controls. A cross-over point for the perturbation occurred at C8-9, which is about 12-14A into the membrane. This is the approximate depth of the hydrophobic pocket shown in pancreatic phospholipase A2 [Drenth et al. (1976) Nature (Lond.) 264, 373 377], a protein likely to be homologous to the basic subunit of the toxin. At all temperatures, rotational lipid motion was inhibited by the toxin as indicated by the steroid probe. The electron spin-resonance spin-label results are interpreted in terms of the partial penetration of the basic subunit of the intact toxin into the membrane, disordering the ordered chains at low temperature and ordering the disordered chains at physiological temperatures. The purified individual toxin subunits did not perturb the membrane lipids at physiological temperatures implying that both subunits must be associated for activity of the toxin which is confirmed by toxicity studies. [ABSTRACT FROM AUTHOR]

Salmonella minnesota R 595 (Rc) and other Salmonella strains incorporate cis-Δ9-16:1 (paimitoleic acid) at the expense of mainly dodecanoic acid into the lipid-A portion of lipopolysaccharides, when the cells are grown at low temperature (12 °C). It has recently been shown, that in S. minnesota R 595 grown at 37 °C dodecanoic acid is linked to the 3-hydroxyl group of an amide-bound 3-hydroxytetradecanoic acid. The present data suggest, that cis-Δ9-16:1 occupies the same position in lipid A (12 °C). [ABSTRACT FROM AUTHOR]

The transformation of sarcoplasmic reticulum in last-twitch rabbit muscle by low-frequency indirect stimulation was studied. Peptide pattern analyses and ATPase activities revealed transformation of the sarcoplasmic reticulum into a slow-twitch muscle type to be completed after 30 days. Concomitant changes iii the lipid phase consisted in a decrease of' the phospholipid/protein ratio, a decrease in the phosphatidyicholine content and in changes of the saturated fatty acid moiety of the phospholipid fraction. Significant increases were seen in content of lysophosphatidylcholine (lysolecithin) and in nonesterified fatty acid. Parallel increases in lysolecithin acyl- transferase activity indicated an enhanced phospholipid turnover. The changes in the phospholipid matrix did not lead to a complete transformation. Moreover, the decrease in Ca2+ uptake and Ca2+ -dependent ATPase activity preceded most of the changes in the phospholipids. It appears thus that these alterations occurred independently. [ABSTRACT FROM AUTHOR]

Modified phosphatidylcholine and sphingomyelin containing an anthryl end group attached to one of the fatty acyl chains were used as fluorescent probes in an investigation of the molecular organization of human high-density lipoproteins (HDL). Monolayer experiments and NMR measurements showed the anthryl-labeled lipids to mimic closely the corresponding host phospholipids, the fluorophores being located near to the terminal CH3 groups of the fatty acid residues. The above fluorescent phospholipid probes made it possible for the first time to study differentially the behavior of phosphatidylcholine and sphingomyclin in HDL. The probes were shown to interact in a different way with the apoprotein tryptophans and to be non-randomly distributed at the surface of the globules. The probable sphingomyclin binding site of apolipoprotein A-I was defined. Evidence was obtained suggesting the existence in high-density lipoproteins of two slowly exchanging phospholipid pools: one strongly bound to apoproteins, and the other free or loosely bound. Fluorescence parameters characterizing the fluidity of HDL phospholipids and their interaction with the apoprotein tryptophans were found to correlate with the HDL cholesterol level. The possible significance of the obtained results for a better understanding of the relation of high-density lipoproteins to coronary heart diseases is discussed. [ABSTRACT FROM AUTHOR]

Investigates whether a block in lipid production causes any effect on synthesis and assembly of some specific outer membrane proteins. Permeability of the outer membrane towards various nutrients; Bacterial strains and growth conditions; Inhibition of fatty acid synthesis.

The chemical structure of the lipid A component of the lipopolysaccharide from Vibrio cholerae95R was studied. After sequential degradation a reduced D-glucosamine disaccharide was isolated from lipid A and, after permethylation, shown by combined gas-liquid chromatography/mass spectrometry to be β1,6-linked. The disaccharide is substituted with a phosphate group, ester-bound to the non-reducing glucosamine (GlcN) residue and a pyrophosphorylethanolamine group (PP-Etn) linked to C-1 of the reducing glucosamine residue. This backbone structure is shown in the following formula: P-GIcN(β1-6)GIcN-1-PP-Etn. The amino groups of the glucosamine disaccharide are substituted by D-3-hydroxytetradecanoic acid; tetradecanoic, hexadecanoic and a D-3-O-(D-3-hydroxydodecanoyl)-dodecanoic acid residue are linked to hydroxyl groups. A similar fatty acid composition was detected in lipopolysaccharides from Inaba, Ogawa and NAG strains of V. cholerae. [ABSTRACT FROM AUTHOR]

Lipid mixtures from chloroplast envelope and thylakoid membranes were isolated after different labelling times in vivo and in vitro and separated into major components. The isolated compounds were subjected to analyses such as separation of molecular species, determination of radioactivity in fatty acids and water-soluble hydrolysis products and radio gas-liquid chromatography of fatty acid mixtures. In the case of monogalactosyl and digalactosyl diacylglycerol these procedures were also applied to several individual molecular species. To investigate the extent of de novo synthesis these species were also used for methylation studies and their fatty acids subjected to α-oxidation. In envelope membranes diacylglycerols and monogalactosyl diacylglycerols may each be separated into several distinct and non-mixing pools. Molecules made de novo with oligoene fatty acids are very efficient substrates for galactosylation in vivo. The time-dependent changes in patterns of galactolipid molecular species may indicate a desaturation of acyl chains operating in close contact to intact lipids. After isolation, envelopes incorporated UDP-[14C]galactose into completely different patterns of galactolipids and molecular species pointing to changed properties of this membrane system or to a loss of regulatory factors. [ABSTRACT FROM AUTHOR]

The distribution of radioactivity from intravenously administered cis-9-[1-14C]octadecenol into various tissues of the rat was studied as a function of time. The pattern of incorporation of radio-activity into alkyl, alk-1-enyl and acyl moieties of the lipids in heart, lungs, liver, intestine, kidney, brain and plasma revealed that oxidation of the long-chain alcohol and esterification of the resulting fatty acid to a wide variety of lipids are by far the most predominant reactions. Acylation of the long-chain alcohol is observed especially in liver, which appears to be the major site of bio-synthesis of wax esters. Alkylation of the long-chain alcohol to alkoxylipids occurs in most tissues, most predominantly in the heart. [ABSTRACT FROM AUTHOR]

An ordered hexagonal lattice structure with a lattice constant of about 7 nm was reconstituted from outer membrane protein O-8 and/or O-9 and lipopolysaccharide [H. Yamada and S. Mizushima, J. Bacteriol. 135, 1024-1031 (1978)]. Using this reconstitution system, the interaction between O-8 and lipopolysaccharide was studied and the following results were obtained. At least one lipopolysaccharide molecule per one 0-8 trimer was required for the hexagonal lattice formation. The lattice constant of the hexagonal lattice formed under the conditions was about 6.5 nm. in the presence of a larger amount of lipopolysaccharide, the lattice constant increased to 7.5 nm, being almost the same as that observed in the dodecylsulfate-treated cell envelope. The lattice constant observed with the heptoseless lipopolysaccharide was also 6.5 nm when the lipopolysaccharide/O-8 ratio was low. Although the increase of the lattice constant was observed upon further addition of the lipopolysaccharide, it was appreciably smaller than that with the wild-type lipopolysaccharide. A hexagonal lattice was also formed when lipopolysaccharide was replaced by an equivalent amount of lipid A or even fatty acids. The lattice constant was the same as that with the wild-type lipopolysaccharide when the lipid/protein ratio was low. However, contrary to the case of lipopolysaccharide, the lattice constant remained almost unchanged even when a larger amount of either lipid A or fatty acid was added to the reconstitution system. A slight increase in the lattice constant was observed only when an extremely large amount of lipid A was added to the reconstitution system. These results suggest that (1) both the lipid A moiety and the polysaccharide moiety of lipopolysaccharide participate in the interaction with the 0-8 trimer, (2) in the lipid A moiety the fatty acid region primarily participates in the hexagonal arrangement of the 0-8 trimer and the minimum requirement of lipopolysaccharide for the lattice formation is most probably one lipopolysaccharide molecule per 0-8 trimer and (3) the polysaccharide moiety, probably both the 3-deoxy-D-mannooctulosonate region and the distal end region including heptose, are involved in an interaction of lipopolysaccharide with the 0-8 trimer to give a proper lattice conformation. [ABSTRACT FROM AUTHOR]

The isolation of the soluble form of the Enterobacteriaceae common antigen from Salmonella montevideo was achieved by a combination of the phenol/water method and the phenol/chloroform/ petroleum ether extraction procedure. A phenol-soluble fraction highly enriched in the antigen was obtained which was further purified by DEAE-cellulose chromatography. A fraction eluted with 0.9 M ammonium acetate/methanol was highly active in coating erythrocytes for passive hemaggluti- nation with antisera specific for enterobacterial common antigen and was an active inhibitor of the hemagglutinating system for this antigen. Chemical analyses showed enterobacterial common antigen to be a linear polymer of 1,4-1inked N-acetyl-D-glucosamine and N-acetyl-D-mannosaminuronic acid units esterified to a small extent by palmitic and acetic acids. These amino sugar and fatty acid components represent about 65–70% of the material. The presence of additional still unknown lipid components which might account for the missing 30% and for the low solubility of the isolated antigen in water is discussed. The molecular weight of the readily soluble part of the inhomogeneous isolated enterobacterial common antigen was determined by sedimentation studies in an analytical ultracentrifuge using methanol as solvent; it was found to be 2700. [ABSTRACT FROM AUTHOR]

The fatty acid composition of the lipid A moiety of the lipopolysaccharide and phospholipid fractions of Proteus mirabitis changed significantly on varying the growth temperature. A decrease in the growth temperature from 43°C to 15°C resulted in a decrease in the palmitic acid content of the lipopolysaccharide from 19.4% of total fatty acids at 43°C to 1.4% at 15°C, and by the appearance of an unsaturated fatty acid residue, hexadecenoic acid. Changes in the 3-hydroxymyristic acid content of the lipid A were minimal. The decrease in the growth temperature also resulted in a decrease in the saturated fatty acid content of the phospholipid fraction, which was accompanied by an increase in their fluidity, as measured by the freedom of motion of spin-labeled fatty acids incorporated into dispersions made of the phospholipids. Nevertheless, the fluidity obtained with membrane phospholipids extracted from the cells grown at various temperatures were essentially the same when fluidity was determined at the growth temperature, supporting the hypothesis that variations in the fatty acid composition of membrane phospholipids serve to produce membranes having a constant fluidity at different temperatures of growth. [ABSTRACT FROM AUTHOR]

1. The acyI-acceptor specificities of the l-acylglycerolphosphate acyltransferase and l-acylglycerophosphorylcholine acyltransferase resolved from rat liver microsomes have been investigated with various synthetic 1-acyl-sn-glycerol 3-phosphate and 1-acyl-sn-glycero-3-phosphorylcholine derivatives differing in their fatty acid constituent (myristic. palmitic, stearic, oleic, linoleic or arachidonic acid) as well as with various 1-acyl-sn-glycerophospholipid analogues carrying different polar head groups (phosphorylcholine, phosphoryldimethylethanolamine, phosphorylmonomethylethanolamine, phosphorylethanolamine, phosphorylethanol or phosphate). 2. The activities of the two acyltransferases are virtually not affected by the fatty acid constituent of the respective acyt acceptors, except that the l-stearoyl and l-arachidonoyl derivatives are somewhat less effective acyl acceptors for both enzymes. 3. The 1-acylglycerophosphorylcholine acyltransferase utilizes several acyl acceptors differing in the polar head group with the following order of effectiveness: 1-acyl-sn-glycero-3-phosphorylcholine > 1-acyl-sn-glycero-3-phosphoryldimethylethanolamine > 1-acyl-sn-glycero-3-phosphorylmonomethylethanolamine ≈ l-acyl-sn-glycero-3-phosphorylethanolamine, l-Acyi-sn-glycero-3-phosphorylethanol and 1-acyl-sn-glycerol 3-phosphate are ineffective. In contrast, the 1-acylglycerolphosphate acyltransferase is highly specific for l-acyl-sn-glycerol 3-phosphate. 4. The fatty acid constituent of the acyl acceptors exerts essentially no effect on the acyl-donor specificity of each enzyme except in the case of l-arachidonoyl-sn-glycero-3-phosphorylcholine. Furthermore, the acyl-donor specificity of the l-acylglycerophosphorylcholine acyltransferase is virtually not affected by the polar head group of the acyl acceptor. 5. The results obtained in this work and in our previous investigations support the view that the substrate specificities of glycerophosphate acyltransferase, l-acylglycerolphosphate acyltransferase and l-acylglycerophosphorylcholine acyltransferase make an essential contribution to the nonrandom fatty acid distribution in naturally occurring glycerolipids. [ABSTRACT FROM AUTHOR]

Presents the nomenclature of lipids recommended by the IUPAC-IUB Commission on Biochemical Nomenclature. Generic terms for fatty acids, neutral fats, long-chain alcohols and long-chain bases; Glycerol derivatives; Symbols and abbreviations for phospholipids.

A procedure is described for the selection of conditional 3-deoxy-D-manno-octulosonic-acid — Lipid A mutants which depends on temperature sensitivity for both synthesis of complete lipopolysaccharide and for growth. Using this procedure new types of mutants were isolated which cease growth and accumulate lipid A precursors following a shift to nonpermissive temperatures. All precursor molecules differ in their charge as judged by DEAE-cellulose chromatography. While they all contain glucosamine, phosphate and 3-hydroxymyristic acid, they lack detectable 3-deoxy-D-manno-octulosonic acid (dOclA) as well as the nonhydroxylated fatty acids of the complete lipid A structure. Three mutants proved to be conditionally defective in dOclA metabolism, whereas one seems to be blocked at a relatively early step in lipid A synthesis. The phenotypes of all these mutants appear to be due to single mutations by reversion analysis and by characterization of the temperature-resistant revertants. Studies of these mutants may shed light on the essential role of the complete dOclA—lipid A part of lipopolysaccharides in membrane function. [ABSTRACT FROM AUTHOR]

Infectious PM2 virus paticles could be reconstituted hi vitro from a mixture of nucleocapsid, phospholipids containing cis fatty acids, and proteins I and II. The presence or absence of acyl phosphatidylglycerol, a minor lipid component of the virion, did not affect the reconstitution of infectious particles, even though it was incorporated into the particles when present. When phos- phatidylglycerol was completely replaced by acyl phosphatidylglycerol in the reconstitution mixture, no infectious particles were formed. Lipids containing either cis or trans fatty acids were also used for reconstitution in vitro of the lipid-containing bacteriophage PM2. Regardless of the ratio of phosphatidylglycerol to phosphatidylethanolamine in the reconstitution mixture, infectious particles were formed and had almost the same phospholipid composition when lipids containing cis-palmitoleic acid were used; no infectious particles were obtained when lipids containing trans-palmitoleic acid were used. In the latter case, virus-like particles were, however, formed. Reconstituted particles containing cis fatty acids were infectious when tested on wild type Pseudomonas BAL-31 as well as on the unsaturated fatty acid auxotroph grown in the presence of either cis or trans-palmitoleic acid. Reconstituted particles containing trans fatty acids were not infectious on any of these cells. When trans fatty acids as well as cis fatty acids were present in the reconstitution mixture, then there was a lower yield of infectious particles. Particles with either cis or tram fatty acids had all four viral proteins and adsorbed to BAL-31 host cells in a specific manner. [ABSTRACT FROM AUTHOR]

1. To study the different metabolic behaviour of various stages of development of the insect Ceratitis capitata, the incorporation of labeled decanoic, lauric, myristic, palmitic, stearic, oleic, and linoleic acids into triacylglycerols by insect homogenates was investigated. The time-course of incorporation of labeled fatty acids was firstly studied by using oleic acid; it showed that after 10 min of incubation the levels of radioactivity incorporated into triacylglycerols and those remaining in the free fatty acids were practically unchanged. 2. All labeled fatty acids were efficiently incorporated by larval homogenates; however, most of the radioactivity remained as free fatty acids in the presence of pharate adult homogenates, palmitic, and stearic acids being the most scarcely incorporated by this stage of development of the insect. 3 Plots of triacylglycerol and free fatty acid radioactivities versus the stage of development defined a crossing-zone in coincidence with the larval-pupal apolysis. This metabolic difference between larval and pharate adult homogenates could not be explained through differences in the acyl-CoA synthetase activity of the insect; this enzyme activity was notably higher in pharate adult homogenates than in the larval homogenates whatever would be the nature of the fatty acid. 4. [14C]Triolein was scarcely hydrolyzed by both larval and pharate adult homogenates. 5. Double-label experiments were carried out by incorporating either [³H]oleic acid or [³H]-palmitic acid and [14C]glycerol 3-phosphate by larval and pharate adult homogenates at different incubation intervals. Diacylglycerols, triacylglycerols, and phosphoglycerides were isolated and the 14C/³H molar ratio calculated. Results suggest the existence of a different acyltransferase activity in the different stages of development of the insect. [ABSTRACT FROM AUTHOR]

Three new fucolipids have been isolated from the water-soluble glycolipid fraction of hog gastric mucosa. Fucolipid A and C exhibited blood-group-A activity, whereas Fucolipid B was not active in A-anti-A, B--anti-B and H-anti-H systems. The structures of these glycolipids were identified by partial acid hydrolysis and methylation analysis, as: [This equation cannot be represented into ASCII Text]. [ABSTRACT FROM AUTHOR]

The tapeworm Moniezia expansa contains an extremely abundant cytoplasmic lipid-binding protein (LBP). It is a small protein consisting of 66 amino acids with a molecular mass of 7943 ± 1.5 Da. The amino acid sequence has been established by Edman degradation and confirmed by PCR analysis. The Moniezia LBP shows no sequence similarity with any previously described binding protein, but does show similarity with antigen B from Echinococcus glanulosus and Echinococcus multilocularis and with Taenia crassiceps antigen. The predicted structure for Moniezia LBP shows four helices and a putative tyrosine kinase site on the loop between helix 1 and 2. Each of the four helices has a well defined hydrophobic face. Studies with fluorescent probes suggest a single hydrophobic binding site. Results indicate that the single tryptophan residue in the molecule (Trp41) is involved in ligand binding, and calculation of the Stern-Volmer quenching constant shows that Trp41 is in a relatively hydrophobic environment. [ABSTRACT FROM AUTHOR]

A new structure of a lipid and its covalent linkage to a protein (murein-lipoprotein of the Escherichia coli outer membrane) is described. Glycerylcysteine (S-(propane-2',3'-diol)-3-thio2-aminopropanic acid) at the N-terminal end of the polypeptide chain is the attachment site of two ester-bound fatty acids. An additional fatty acid is bound as amide to the N-terminal group. The diglyceride residue on the cysteine could be derived from the phospholipid pathway since the fatty acid composition is very similar to that of the phospholipids from the same cells. In contrast, 65% of the amide-linked fatty acid is palmitate. The main fatty acids are palmitic acid (53%), cis-vaccenic acid (20.7%), 9,10-methylene-hexadecanoic acid (10.6%) and palmitoleic acid (9.4%). The structure of glycerylcysteine was established by chemical degradation of the compound containing the fatty acids, by incorporation studies of [35S]sulfate, [35S]cysteine, [14C]cystine, [methyl-³H]methionine and [2-³H]glycerol and by chemical synthesis. Glycerylcysteine was isolated as a constituent of the peptide (Ser)-Ser-Asn-Ala-Lys. The C-terminal part of the lipopeptide sequence overlaps with the N-terminal end of the known sequence of the polypeptide chain. Its N-terminal position was confirmed by isolation of the N-terminal polypeptide fragment (position 1-31) after cleavage with cyanogen bromide. This contained the lipid. [ABSTRACT FROM AUTHOR]

The walls of Nocardia kirovani are composed of three main constituents: the peptidoglycan matrix, a polysaccharide polymer and a variety of free and bound lipids. The free lipids represent 17.5% (dry weight) of the walls and consist for the major part of C16-18 fatty acids and nocardic acids, and for the minor part, of nocardones, triglycerides and carotenoid pigments. The nocardic acids were identified as tri- and tetra-unsaturated, α-branched, β-hydroxylated compounds C58H110O3--C66H124O3, the nocardones as tri- and tetra-unsaturated ketones C57H106O--C63H118O, and the main carotenoid pigment as phlei-xantophylle palmitate. Esters of glycerol with C14C16C18 fatty acids and, for some of them, with odd numbered poly-unsaturated acids containing 35 to 45 carbon atoms, were also identified, Bound lipids represent about 20% (dry weight) of the walls and consist mainly of nocardic acids probably ester-linked to an arabinogalactan polymer. The peptidoglycan (about 40% dry weight) is composed of β-1,4-N-acetylglucosaminyl-N-glycolylmuramic acid disaccharide units that are substituted by diamidated L-Ala-D-αGln-(L)- A2pm-(D)-NH2 tripeptides and diamidated L-Ala-D-αGln-(L)-A2pm-(D)-NH2(L)-D_Ala tetrapeptides, where A2pm is meso-diaminopimelic acid.Crosslinking between some of the peptide units is mediated through D-Ala-(D)-A2pm linkages (peptidoglycan of ehemotype I). [ABSTRACT FROM AUTHOR]

1. Deacylation of phosphatidylcholine by the lipolytic acyl hydrolase enzyme in homogenates of potato tubers was stimulated by endogenous free fatty acids in the homogenates. 2. Partially purified enzyme preparations were inactive in the absence of surface active agents. 3. The fatty acid-stimulated enzymic deacylation of phosphatidylcholine showed a pH optimum between 5.5 and 6.0 and was reversed by bovine serum albumin. 4. Free fatty acids were more effective than other lipids and surface active compounds studied. 5. Long-chain cis-unsaturated fatty acids were most effective. 6. Enzymic hydrolysis of phosphatidylethanolamine showed a similar stimulation by free fatty acids but hydrolysis of lyso-phosphatidylcholine, phosphatidyiglycerol, phosphatidic acid galactolipids or monoglycerides was not stimulated. 7. Similar stimulation by linoleic acid of the enzymic deacylation of membrane-bound phospholipid was observed and found to be prevented by bovine serum albumin. 8. Electron microscope studies suggested that free fatty acids had a marked effect on the physical state of phosphatidylcholine in aqueous dispersions. [ABSTRACT FROM AUTHOR]

A number of lipopolysaccharides derived from Salmonella and Escherichia coli S and R mutant strains were tested for toxicity and anticomplementary activity in the absence of added antiserum. Although all preparations were toxic, only a few exhibited high anticomplementary activity, while others proved to be of low or negligible activity. It was found that isolated lipid A from both active and reactive lipopolysaccharides was strongly anticomplementary as well as toxic, when made water-soluble with the aid of suitable carriers. Treatment of R form lipopolysaccharide with Mg2+ or Ca2+ led to complete precipitation of the lipopolysaccharide with consequent loss of toxicity and anticomplementary activity. This treatment had practically no effect on the anticomplementary activity and toxicity of S form lipopolysaccharides. When lipopolysaccharide, after reaction with complement, was reisolated and purified, the resulting preparation was found to be non-toxic and of negligible anticomplementary activity. No detectable alterations in either the sugar or the fatty acid composition could be detected. The only significant change was the loss of solubility in water. Treatment of the reisolated lipopolysaccharide with EDTA completely restored solubility m water, toxicity, and anti-complementary activity. [ABSTRACT FROM AUTHOR]

1. The cleavage of the β-ester bond of the phospholipids in the membranes of the sarcoplasmic reticulum by phospholipase A increases the permeability of the membranes for calcium whereby the ATP driven calcium storage is abolished. The activity of the calcium dependent ATPase remains unimpaired. The splitting products of the phospholipids which are composed of unsaturated fatty acids and prevailingly saturated lysolecithins are firmly attached to the membranal protein. They are removed from the protein by bovine serum albumin. The calcium dependent ATPase activity and the phosphoryl-transfer from ATP to the membranal protein are abolished thereby. 2. Unsaturated fatty acids restore the phosphoryl transfer reaction and the calcium dependent ATPase. Lysolecithin restores the ATPase activity nearly to the same extent but the phosphoryl transfer reaction is not reactivated. The accumulation of calcium is not restored either by unsaturated fatty acids or lysolecithin. 3. The calcium dependent ATPase reactivated by fatty acids is more sensitive towards prenylamine than the ATPase reactivated by lysolecithin. Prenylamine is bound to the vesicles activated by fatty acids whereas the vesicles reactivated with lysolecithin do not bind the drug. [ABSTRACT FROM AUTHOR]

Identifies acylglucoses as major components of the soluble lipids of Corynebacterium diphtheriae, Mycobacterium smegmatis and bacillus-calmette-guerin, grown in the presence of glucose. Mass spectrometry of the methylated lipids; Periodate oxidation; Esterification of fatty acids to position six of the glucose.

The "Quacking" mouse in a mutant which has an inherited disease involving the process of myelination in the central nervous system. Fractionation of brain lipids and fatty acid methyl ester analysis of each lipid isolated have been performed. No qualitative abnormalities have been detected, either in ethanolamine, serine and choline phospphoglycerides, or in cholesterol. Proof has now been obtained that the considerable reduction in long chain fatty acid (C24), occurs in cerebrosides, sulphatides (where they are normally major constituents) and in sphingomyelin. Long chain hydroxylated fatty acids are comparatively less diminished than non-hydroxylated one. This metabolic defect, detected in all the sphingolipids that contain this type of fatty acids could be in favour of a mutation related to fatty cid elongation which is very important at the time of myelin formation. [ABSTRACT FROM AUTHOR]

Two different strains of Brucella abortu, strain 1119 and strain Scherle II, were grown on solid media; strain 1119 was harvested after approximately 70 h, strain Scherle II was harvested at different ages of the culture up to 72 h. The "free" total lipids were extracted and from these the neutral lipids were prepared and analyzed. The following results were obtained. Strain 1119 contains 4.5% free lipids of bacterial dry weight. Strain Scherle H contains decreasing amounts of free total lipids from approximately 6 % to 1.4 % as the age of the culture increases. On a weight basis the free total lipids of strain 1119 contain 8.1 % neutral lipids. The neutral lipids of strain Scherle II decrease from more than 60% to approximately 24 % (of free total lipids) with increasing age of the culture. The amount of phospholipids, however, remains comparatively constant (in relation to the percentage of total lipids) with increasing age of the culture of strain Scherle II. The results indicate that polar lipids other than phospholipids accumulate as the age of the culture increases, but there is no net storage of lipids. The neutral lipids of strain 1119 contain approximately 30% (on a weight basis) of ubiquinone-50 (corresponding to 1.2 μmoles/g bacterial dry weight). Strain Scherle II also contains uhiquinone-50, but in amounts demonstrable by thin-layer chromatography only after an age of 36-38 h. Ubiquinone-50 has hitherto been found only in a few bacterial species, while most bacterial species contain lower isoprenologs of ubiquinone. The neutral lipids of strain 1119 contain 51 % (on a weight basis) of diglycerides, consisting of the 1,3- and the 1,2-isomers. In strain Scherle II only 1,2-diglycerides were found. The component fatty acids of the diglycerides of strain 1119 consist of approximately 55% (on a weight basis) of C19 cyclopropane acid (lactobacillic acid). The lactobacillic acid/cis-vaccenic acid ratio is fairly independent of the age of the culture of strain Scherle IL. The amount of unesterified fatty acids is lower in strain 1119 (4.9 % of the neutral lipids, on a weight basis) than in strain Scherle II (49 or 67 %, according to the culture conditions). Both strain 1119 and strain Scherle II COhen probably small amounts of triglycerides, monoglycerides and long-chain hydrocarbons. The possible significance of the results in the classification of Brucella is discussed. [ABSTRACT FROM AUTHOR]

1. The phospholipids of rabbit erythrocytes were separated by thin-layer chromatography on silica gel HR and determined quantitatively by the molybdenum blue method. Prior to thinlayer chromatography phosphatidic acid and phosphatidyl inositol were concentrated by column chromatograph. 2. The total phospholipid contents were 313 ± 27 amoles per erythrocyte and 289 ± 13 amoles per ghost. The proportions of the individual phospholipids of erythrocytes in moles % were 36.3 of phosphatidyl choline, 32.6 of phosphatidyl ethanolamine, 15.7 of sphingomyelin, 12.4 of phosphatidyl serine, 1.6 of phosphatidic acid, 1.3 of phosphatidyl inositol, and <0.1 of lysophosphatidyl choline. The same distribution was obtained in ghosts with the exception of a significantly higher concentration of sphingomyelin. 3. The fatty acid composition of phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, ceramide trisaccharide, and sphingomyelin was analysed by gas-liquid chromatography after the lipids had been fractionated by preparative thin-layer chromatography. 4. For identification of the fatty a acids, their methylesters were isolated on silica gel G-silver nitrate plates according to degree of saturation. 5. Typical of sphingotipids were the tow concentration of linoleic acid, the absence of arachidonic acid, the presence of lignoceric acid and the very high concentration of nervonic acid. 6. Phosphatidyl choline and phosphatidyl ethanolamine were hydrolysed by phospholipase A (ophiophagus hannah) in order to analyse the fatty acid distribution of the two positions. In position 1 of phosphatidyl choline and phosphatidyl ethanolamine the saturated fatty acids amounted to 83.6% and 65.6%, respectively. Unsaturated fatty acids, especially oleic acid and linofeic acid, also occurred in position 1. These acids were the main components in position 2. [ABSTRACT FROM AUTHOR]

The ‘Quaking’ mouse is a recessive autosomal mutant characterized by a deficient myelination of the central nervous system. The disease is recognized at about the twelfth day after birth and reaches its full expression by about three weeks. The animal has an unsteady gait and a marked tremor of the hind quarters; epileptic fits are induced by sensory stimulations at the adult age. This mutation apparently involves the process of myelin formation; there is no evidence of destruction. The analysis of brain fatty acids and lipids was undertaken to find out if the myelin deficiency involves an inborn error in the metabolism of one of its major constituents. ‘Quaking’ males aged from seven to ten weeks were compared to apparently normal litter-mates. At this stage, myelination is achieved. Brain lipids are diminished, especially galactolipids. Qualitative modifications of cerebrosides, sphingomyelin and sulphatides have been detected by mono and two dimensional thin layer chromatography. The proportion of long chain fatty acids (especially C24) is greatly diminished, as shown by gas chromatography. This is true for both cerebrosides and sphingomyelin. In conclusion, the long chain fatty acids of galactolipids and sphingomyetin are considerably diminished in the ‘Quaking’ mouse. Whether it is a cause or a consequence of myelination deficiency remains to be proved, although the importance of the alteration is in favour of the first hypothesis. [ABSTRACT FROM AUTHOR]

An analysis of the lipids of the fat body of Locusta migratoria showed that approximately 97% are triglycerides and 2-3% diglycerides; free fatty acids and phospholipids were present only in small amounts. In the hemolymph, diglycerides and phospholipids were the major lipid components; free fatty acids were present in very small amounts, triglycerides were absent. The concentration of the diglycerides in the hemolymph was found to increase with the age of the locust and during sustained flight; the phospholipids remained constant. The concentration of the free fatty acids in the tissue and hemolymph was also increased during flight. When fat body tissue was incubated in vitro with [1-14C]palmitate, the acid was incorporated into the di- and triglycerides of the tissue. The specific activity of the diglycerides was at least 50 times higher than that of the triglycerides. When prelabeled tissue was transfered into a medium containing hemolymph, diglycerides were released into the medium. The amount of diglyceride released was dependent on the time of incubation and on the amount of hemolymph which was added to the medium. Although the amount of diglycerides which was released, was greater than their concentration in the tissue, the amount of the latter did not change. However, their specific activity was very markedly reduced. When the fat body tissue was prelabeled in vivo and the specific activity of the di- and triglycerides was identical, the specific activity of the diglycerides was not reduced during diglyceride release. When fat body tissue of locusts after flight was incubated with [1-14C]palmitate, incorporation of the acid into the diglycerides was very markedly reduced. This inhibition was reversed by the addition of glucose to the medium. When prelabeled tissue of locusts after flight was incubated in hemolymph obtained from the same locusts, diglycerides and free fatty acids were released into the medium. [ABSTRACT FROM AUTHOR]