Showing papers on "Lipid biosynthesis published in 1987"

Total lipid production of the green alga nannochloropsis sp qii under different nitrogen regimes

Abstract: The green alga Nannochloropsis sp. QII was cultivated in media with sufficient and growth-limiting levels of nitrogen (nitrate). Nitrogen deficiency promoted lipid synthesis yielding cells with lipids comprising 55% of the biomass. The major lipids were triacylglycerols (79%), polar lipids (9%) and hydrocarbons (2.5%). The polar lipids consisted of a broad range of phospholipids, glycolipids and sulfolipids. Other lipids identified were pigments, free fatty acids, saponifiable and unsaponifiable sterol derivatives, various glycerides, a family of alkyl-1, 4-dioxane derivatives and a series of alkyl- and hydroxy-alkyl-dimethyl-acetals. Experiments in which /sup 14/CO/sub 2/ was provided at different times in the growth cycle demonstrated that enhanced lipid biosynthesis at low nitrogen levels resulted principally from de novo CO/sub 2/ fixation.

Peroxisomes in Biology and Medicine

Abstract: One Peroxisomes and Lipid Biosynthesis.- Morphogenesis of Peroxisomes in Lipid-Synthesizing Epithelia.- Peroxisomes in Sebaceous Glands: Biosynthetic Role and Hormonal Regulation.- Peroxisomal Alkyl-Dihydroxyacetonephosphate Synthase and a Related Enzyme in Microsomes (Microsomal Synthase) of Rat Liver.- Localization of 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase in Rat Liver Peroxisomes.- Dolichol Metabolism and Peroxisomes.- Liver Peroxisomes and Bile Acid Formation.- Peroxisomes, Proliferation, and the Synthesis of Phospholipids.- Evidence for a Link Between Peroxisomes and the Nonspecific Lipid Transfer Protein (Sterol Carrier Protein 2) in Rat and Human Liver.- Two Peroxisomes and Lipid Catabolism.- Comparison of Enzymes of Lipid ?-Oxidation in Peroxisomes and Mitochondria.- Cloning and Structural Analysis of the Genes for Peroxisomal ?-Oxidation Enzymes.- Immunoelectron Microscopy of Peroxisomal Enzymes Their Substructural Association and Compartmentalization in Rat Kidney Peroxisomes.- ?-Oxidation Systems in Eukaryotic Microorganisms.- Higher Plant Peroxisomes and Fatty Acid Degradation.- Physiological Role of Peroxisomal Beta-Oxidation.- Three The Peroxisomal Membrane.- Permeability of the Peroxisomal Membrane.- Peroxisomal Properties with Potential Regulatory Implications: Selective ATP Requirement for Fatty Acid Oxidation and Membrane Protein Phosphorylation.- Glyoxysomal Membrane Electron Transport Proteins.- The Alkaline Lipase of the Glyoxysomal Membrane Is a Glycoprotein.- A Proton Translocating ATPase Is Associated with the Peroxisomal Membrane of Yeasts.- Study on Membrane Fluidity of Liver Peroxisomes.- Four Metabolic Pathways (Other than Lipids) in Peroxisomes.- Peroxisomal Glycolate Metabolism and the C2 Oxidative Photosynthetic Carbon Cycle.- Peroxisomal Oxidases and Their Probable Role in Controlling Animal Metabolism.- Amino Acid Metabolism in Animal Peroxisomes.- Aldehyde Dehydrogenase in Mammalian Peroxisomes.- Five Peroxisomes and Drugs.- Induction of Hepatic Peroxisome Proliferation by Xenobiotics.- Phenotypic Properties of Preneoplastic and Neoplastic Hepatic Lesions Induced by Peroxisome Proliferators in Rats.- The Relationship Between the Levels of Long-Chain Acyl-CoA and Clofibryl-CoA and the Induction of Peroxisomal ?-Oxidation.- Prevention of Peroxisomal Proliferation by Carnitine Palmitoyltransferase Inhibitors in Cultured Rat Hepatocytes and In Vivo.- Use of Primary Cultures of Adult Rat Hepatocytes to Study the Mode of Action of the Peroxisome Proliferator Nafenopin.- Effects of Antilipolytic Drugs on Hepatic Peroxisomes.- Induction of Cytochrome P450 and Peroxisome Proliferation in Rat Liver by Perfluorinated Octane Sulphonic Acid (PFOS).- Risks and Benefits of Agents Which Induce Hepatic Peroxisome Proliferation.- Automatic Image Analysis for Morphometric Studies of Peroxisomes.- Six Peroxisomes and Human Diseases.- Pathogenesis of Zellweger's Cerebro-Hepato-Renal Syndrome and Related Peroxisome Deficiency Diseases.- Observations About the Phenotype of Peroxisomal Disorders.- Biochemical Analysis in Peroxisomal Disorders.- Complementation Analysis of Peroxisomal Diseases by Somatic Cell Fusion.- Fatty Acid Metabolism in Cultured Skin Fibroblasts from Patients with Peroxisomal Disorders: Lignoceroyl-CoA Ligase Deficiency in Childhood Adrenoleukodystrophy.- Liver Peroxisomal Oxidizing Activities in Physiological and Pathological Conditions.- Deficiency of Peroxisomal Alanine: Glyoxylate Aminotransferase in Primary Hyperoxaluria Type 1.- Retrospective Immunocytochemical Demonstration of Peroxisomal Enzymes in Human Liver Biopsies Processed Conventionally for Light and Electron Microscopy.- Seven Biogenesis of Peroxisomes.- to the Session on Biogenesis.- Biogenesis of Peroxisomes in Rat Liver and Candida Tropicalis.- Biogenesis of Rat Liver Peroxisomal Membrane Polypeptides.- Biogenesis of Plant Microbodies.- Biogenesis of Glycosomes (Microbodies) in the Trypanosomatidae.- Metabolic Significance and Biogenesis of Microbodies in Yeasts.

Dynamics of Membrane Lipid Metabolism and Turnover

Abstract: INTRODUCTION AND PERSPECTiVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 43 INTRACELLULAR LOCATION OF LIPID BIOSYNTHESIS 44 Phospholipids 44 Cholesterol 45 Glycolipids 45 INTRACELLULAR LOCATION OF LIPIDS.. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . 46 ASSEMBLY OF THE LIPID BILAYER IN THE ENDOPLASMIC RETICULUM . . . . 48 INTRACELLULAR TRANSPORT OF LIPIDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 50 Cholesterol 50 Phospholipids 54 TURNOVER OF LIPIDS . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .. .. .. .. 58

Effect of antifungal agents on lipid biosynthesis and membrane integrity in Candida albicans.

Abstract: Eight antifungal agents were examined for effects on lipid biosynthesis and membrane integrity in Candida albicans. Lipids were labeled in vivo or in vitro with [14C]acetate and analyzed by thin-layer and gas chromatography. Membrane integrity was measured by a recently developed [14C]aminoisobutyric acid radiolabel release assay. The imidazole antifungal agents miconazole, econazole, clotrimazole, and ketoconazole, at concentrations inhibiting ergosterol biosynthesis (0.1 microM), decreased the ratio of unsaturated to saturated fatty acids in vivo but not in vitro. Similarly, naftifine, tolnaftate, and the azasterol A25822B, at concentrations inhibiting ergosterol biosynthesis (10, 100, and 1 microM, respectively), decreased the ratio of unsaturated to saturated fatty acids in vivo only. This suggests that the effect on fatty acids observed with ergosterol biosynthesis inhibitors may be secondary to the effect on ergosterol. With imidazoles, oleic acid antagonized inhibition of cell growth but not inhibition of ergosterol. This suggests that, with the C-14 demethylase inhibitors, decreased unsaturated fatty acids, rather than decreased ergosterol, are responsible for growth inhibition. Cerulenin, previously reported to be a potent inhibitor of both fatty acid and ergosterol biosynthesis, was found in the present study to inhibit the former (at 5 microM) but not the latter (up to 100 microM). Of the antifungal agents tested, econazole and miconazole (at 100 microM) produced complete release of [14C]aminoisobutyric acid, which is consistent with membrane damage.

Reconstitution of a phospholipid flippase from rat liver microsomes

Abstract: The endoplasmic reticulum is the principal site of synthesis and initial incorporation of membrane lipids in eukaryotic cells; the enzymes of glycerolipid biosynthesis are exclusively located on its cytoplasmic surface. To maintain a phospholipid bilayer in this organelle, newly synthesized phospholipids must be translocated to the lumenal surface. Consistent with this are measurements indicating that movement of phospholipids across microsomal membranes is rapid, with a half-time less than 5 min (refs 3 and 4). Rapid movement of phospholipids has also been detected across the plasma membrane of Bacillus megaterium, another site of de novo lipid biosynthesis. The rapid transmembrane movement of phosphatidylcholine has not been detected, however, in vesicles prepared from microsomal lipids. These latter data suggest involvement in the endoplasmic reticulum of a phospholipid-translocating protein, as was first proposed by Bretscher who called it 'flippase'. Here we report reconstitution of a phospholipid flippase from rat liver microsomes into lipid vesicles.

The function of acyl carrier protein in the synthesis of membrane-derived oligosaccharides does not require its phosphopantetheine prosthetic group

Abstract: An enzyme system catalyzing the synthesis of the beta 1,2-linked glucan backbone of the membrane-derived oligosaccharides of Escherichia coli from UDP-glucose has an essential requirement for the E. coli acyl carrier protein (ACP). This finding was surprising, because all other characterized functions of ACP involve acyl thioester residues linked to the phosphopantetheine moiety covalently bound to ACP. We now report that the activity of ACP in the synthesis of membrane-derived oligosaccharides is not altered by treatment with the sulfhydryl reagent N-ethylmaleimide nor by complete removal of the phosphopantetheine residue by treatment with a specific phosphodiesterase. The function of ACP in the synthesis of membrane-derived oligosaccharides is thus clearly different from that involved in lipid biosynthesis. We have nevertheless found that the same molecular species of ACP that undergo enzymic acylation with long-chain fatty acid residues also function in the synthesis of membrane-derived oligosaccharides.

Mode of action of lipoic acid in diabetes

Abstract: Metabolic aberrations in diabetes such as hyperglycemia, ketonemia, ketonuria, reduced glycogen in tissues and reduced rates of fatty acid synthesis in the liver are corrected by the administration of lipoic acid. Dithiol octanoic acid is formed from lipoic acid by reduction and substitutes for Coenzyme A in several enzymatic reactions such as pyruvate dehydrogenase, citrate synthase, acetyl Coenzyme A carboxylase, fatty acid synthetase, and triglyceride and phospholipid biosynthesis; but not in the oxidation of fatty acids because of the slow rates of thiolysis of β-keto acyl dithioloctanoic acid. The overall effect of these changes in the key enzymic activities is seen in the increased rates of oxidation of glucose and a reduction in fatty acid oxidation in diabetes following lipoic acid administration.

Presence and regulation of ATP:citrate lyase from the citric acid producing fungus Aspergillus niger.

Abstract: ATP:citrate lyase (EC 4.1.3.8) has been identified in cell-free extracts from the filamentous fungus Aspergillus niger. The enzyme was located in the cytosol. It exhibits an activity at least ten times that of acetate-CoA-kinase (EC 6.2.1.1) during growth on carbohydrates as carbon sources, and is thus considered responsible for acetyl-CoA formation under these conditions. It is formed constitutively and its biosynthesis does not appear to be controlled by changes in the nitrogen or carbon source or type. ATP:citrate-lyase appears to be very labile during conventional purification procedures; a method involving fast protein liquid anion exchange chromatography was thus developed in order to obtain enzyme preparations sufficiently free of enzymes which could interfere with kinetic investigations. This preparation displays commonly known characteristics of ATP:citrate lyase with respect to substrate affinities and cofactor requirements, with the exception that the affinity for citrate is rather low (2.5 mM). No activator was found. The enzyme is inhibited by nucleoside diphosphates, nucleoside monophosphates and palmitoyl-CoA. Regulation of ATP:citrate lyase be the energy charge of the cytosol in relation to lipid or citric acid accumulation is discussed in view of these findings.

Lipid biosynthesis and deposition in genetically lean and fat chickens. Comparative in vivo studies with 14C acetate.

Abstract: 1 1 Following intravenous administration of 14C-acetate to genetically lean or fat chickens, the radioactivity in their liver, plasma, striated muscle and abdominal adipose tissue lipids and that in the breathed out CO2 were studied in function of time 2 2 As compared to the lean ones, the fat chickens showed a higher labelling of their triglyceride fatty acids in the plasma and adipose tissue, but not in the liver 3 3 Thus a higher rate of triglyceride secretion from the liver would be responsible for the higher abdominal fat weight in the fat line chickens

Plant Growth Regulating Properties of Sterol-Inhibiting Fungicides

Abstract: A group of sterol-inhibiting fungicides, diverse with respect to chemical structure but with the same specific mode of action, has been recently introduced for plant disease control (Siegel, 1981). They belong to the chemical class of triazoles, imidazoles, pyrmidines, morpholines, piperazines, and the structures of some of the compounds are illustrated in Figure 6.1 (Kato, 1982). Most of the compounds are highly active in controlling various economically important fungal diseases including, powdery mildew, smut, bunt, and rust fungi. In other words they control a wide range of diseases caused by Ascomycetes, Basidomycetes and Deuteromycetes and they are not used to control Phycomycetes. The sterol-inhibiting fungicides block ergosterol biosynthesis by inhibiting C-14 demethylation reactions. The specific mechanisms of inhibition of ergosterol biosynthesis which eventually curtails membrane synthesis and fungal growth are discussed by Siegel (1981) and Kato (1982). The mode of action of these fungicides as inhibitors of lipid biosynthesis, in particular the sterol component and the effects of other plant growth retardants suggesting possible sites of inhibition are covered in an excellent review by Ragsdale (1977).

Plant lipid biotechnology through the looking glass

Abstract: The biosynthesis of economically important fatty acids has been resolved in recent years. The individua enzymes have been isolated, purified and characterized; the specific compartmentations of these enzymes in the cell have been determined; the flow of precursors required to supply the substrates for fatty acid synthesis has been defined. With these data at hand, a new thrust has been brought forth, namely the input of the concepts of molecular biology to the solution of a number of problems, which until now have not been resolved. If and when these problems are elucidated, application of these new solutions will have a profound effect on the agroeconomics involved in the annual production and consumption of over 50 million metric tons (m MT) of vegetable oil throughout the world. This discussion focuses on some of the problems facing plant scientists in their attempts to understand and control plant lipid biosynthesis. Some possible solutions will be suggested, and the impact of these solutions on the economy of nations will be examined.

Metabolism via the pentose phosphate pathway in rat pheochromocytoma PC12 cells: Effects of nerve growth factor and 6-aminonicotinamide

Abstract: Exposure of rat pheochromocytoma PC12 cells to 0.1 mM 6-aminonicotinamide (6AN) for 24 hours resulted in a 500-fold increase in 6-phosphogluconate indicating active metabolism of glucose via the oxidative enzymes of the pentose phosphate pathway. Amounts of 6-phosphogluconate that accumulated in 6AN-treated cells at 24 hours were significantly increased by treatment of the cells with nerve growth factor (NGF) (100 ng 7S/ml) suggesting that metabolism of glucose via the pentose pathway at this time was enhanced by NGF. This stimulation of metabolism via the pentose pathway is probably a late response to NGF because initial rates of 6-phosphogluconate accumulation in 6AN-treated cells were the same in the presence and absence of NGF. Moreover, amounts of14CO2 generated from 1-[14CO2]glucose during the initial six hour incubation period were the same in control and NGF-treated cells. Specific activities of hexose phosphates labeled from 1-[14CO2]glucose were also the same in control and NGF-treated cells. The observation that 6AN inhibited metabolism via the pentose phosphate pathway but failed to inhibit NGF-stimulated neurite outgrowth suggests that NADPH required for lipid biosynthesis accompanying NGF-stimulated neurite outgrowth from PC12 cells can be derived from sources other than, or in addition to, the oxidative enzymes of the pentose phosphate pathway.

Inhibition of phosphoglucose isomerase allozymes from the wing polymorphic waterstrider, Limnoporus canaliculatus, by pentose shunt metabolites

Abstract: Inhibition of phosphoglucose isomerase (PGI) allozymes from the wing-polymorphic waterstrider, Limnoporus canaliculatus, by three pentose-shunt metabolites was studied at several different temperatures. This was done to determine if the allozymes exhibited a differential ability to participate in lipid biosynthesis via differential partitioning of carbon flux through the pentose shunt versus glycolysis. 6-Phosphogluconate and erythrose-4-phosphate proved to be strong competitive inhibitors of PGI, while sedoheptulose-7-phosphate was a very weak inhibitor. The PGI allozymes from L. canaliculatus were differentially inhibited by 6-phosphogluconate at two of the three temperatures studied. However, this property does not appear to be an adaptive difference between the allozymes but, rather, a correlated effect resulting from variation in substrate binding. Estimates of reaction rates for the allozymes indicate that the differences in inhibition result in no detectable differences in reaction velocities. Thus, no evidence in support of the hypothesis that PGI allozymes from Limnoporus canaliculatus were adapted to function in different metabolic capacities via differential inhibition was obtained in this study. However, the importance of this characteristic in allozymic adaptation in natural populations remains an open question.

Synthesis and Biological Evaluation of Fungal Bioregulators of Sterol Biosynthesis

Abstract: Corey published a leading paper in 196 7 demonstrating that 2, 3-iminosqualene inhibited the cyclization of squalene-oxide to lanosterol in a cell-free system1. In the interim years between then and this seventh international plant lipid symposium, four groups-one each in the United States2, Canada3 another in France4 and Italy4, have firmly established the mechanistic and biological importance of using this and structurally related molecules, e.g. 25-azasteroids5, to interfere with fungal sterol biosynthesis which results in diminished growth response. Industry and biotechnology firms have followed suit in recent years designing analogous inhibitors6, 7 which they believe may have potential promise in plant protection. On the premise that specific N-isopentenoids induce alterations in sterol biosynthesis which in turn may create a pathologic state in the structure and function of membranes of pathogenic fungi, we began a chemical synthesis program in 1984 by preparing blockers targeted at fungal lipid biosynthesis.

Involvement of Macromolecule Biosynthesis in Auxin and Fusicoccin Enhancement of β-Glucan Synthase Activity in Pea

Abstract: In pea stem segments whose cuticle has been made permeable by abrading it, actinomycin D (ActD) and 80S ribosomal protein synthesis inhibitors such as cycloheximide (CHI) inhibit enhancement by indole 3-acetic acid (IAA) of the activity of the cell wall biosynthetic enzyme, glucan synthase I (GS). This supersedes earlier, negative results with inhibitors, obtained with segments having an intact cuticle, which prevents adequate inhibitor uptake. Since these inhibitors also block IAA-stimulated H+ extrusion, which according to earlier results is involved in the GS response, the significance of these inhibitions would be ambiguous without additional evidence. ActD does not inhibit fusicoccin (FC) enhancement of GS activity, which indicates existence of a post-transcriptional control mechanism for GS, but does not preclude involvement of transcription in the GS response to IAA. Although protein synthesis inhibitors such as CHI do not block FC-stimulated H+ extrusion, they do inhibit FC enhancement of GS activity, indicating an involvement of protein synthesis in the GS response to FC, and presumably also to IAA. However, protein synthesis inhibitors (but not ActD) by themselves paradoxically elevate GS activity, less strongly than IAA does but resembling the IAA enhancement in several characteristics. These results suggest that IAA may enhance GS activity at least in part by inhibiting the synthesis or action of a labile repressor of the transcription of, or a labile destabilizer of, mRNA for GS or some polypeptide that enhances GS activity. However, resemblances between the IAA and FC effects on GS suggest that IAA also has a posttranscriptional GS-enhancing action like that of FC. Lipid biosynthesis may be involved in this aspect of the response since both IAA and FC enhancements of GS activity are inhibited by cerulenin.

Oil Seed Rape Acyl Carrier Protein (ACP) Protein and Gene Structure

Abstract: Acyl carrier protein (ACP) plays a central role in lipid metabolism, serving as both a component of plant fatty acid synthetase (1) and as a substrate/cofactor for complex lipid biosynthesis (2). The protein has been purified from a number of plant sources and its amino acid sequence determined for the protein from both barley leaf (3) and spinach leaf (4) material. Both of these two previously mentioned sources of ACP have two detectable forms of the protein (5–6) whilst in seed material only one form has been detected (5). ACP has been shown, using immunological techniques, to be a developmentally regulated protein in maturing soy bean seeds. The activity of the protein appearing just prior to lipid accumulation (7). Despite the importance of this protein in lipid metabolism and the fact that seeds are a major site of lipid synthesis there is no reported literature on the characterization of ACP from seed material.

Lipid Accumulation in Silicon-Deficient Diatoms

Abstract: Previous studies have shown that the lipid contents of the the diatoms Navicula pelliculosa (2) and Cyclotella cryptica (3) increase significantly in response to silicon deficiency. The chemical nature of the lipids produced under these conditions was not determined, however. Furthermore, the biochemical mechanisms responsible for this switch to lipid accumulation have never been elucidated. The research described in this paper was therefore undertaken in an effort to further investigate the regulation of lipid biosynthesis in Si-deficient diatoms.

Lipid metabolic pathways operating in amphibian full-grown oocytes.

Abstract: 1. 1. The utilization of (2-3H)-glycerol in lipid biosynthesis was analyzed in Bufo arenarum and Xenopus laevis full-grown oocytes. 2. 2. The precursor was more actively incorporated in Xenopus laevis oocytes. Neutral glycerides were the lipids displaying the highest levels of radioactivity followed by phosphatidylcholine and phosphatidylethanolamine. 3. 3. After reincubation of prelabeled oocytes in a saline buffer solution, a net fall in labeled phosphatidic acid concomitant with an increase in phosphatidylcholine were detected. 4. 4. The present findings establish that glycerolipid biosynthesis is operative in full-grown oocytes. In addition, Xenopus laevis oocytes seem to be metabolically more active.