Showing papers on "Lipid biosynthesis published in 1993"

Growth rate regulation of Escherichia coli acetyl coenzyme A carboxylase, which catalyzes the first committed step of lipid biosynthesis.

Abstract: Acetyl coenzyme A (CoA) carboxylase catalyzes the synthesis of malonyl-CoA, the first intermediate of fatty acid synthesis. The Escherichia coli enzyme is encoded by four subunits located at three different positions on the E. coli chromosome. The accBC genes lie in a small operon at min 72, whereas accA and accD are located at min 4.3 and 50, respectively. We examined the expression of the genes that encode the E. coli acetyl-CoA carboxylase subunits (accA, accBC, and accD) under a variety of growth conditions by quantitative Northern (RNA) blot analysis. We found a direct correlation between the levels of transcription of the acc genes and the rate of cellular growth. Consistent results were also obtained upon nutritional upshift and downshift experiments and upon dilution of stationary-phase cultures into fresh media. We also determined the 5' end of the accA and accD mRNAs by primer extension and did transcriptional fusion analysis of the previously reported accBC promoter. Several interesting features were found in the promoter regions of these genes, including a bent DNA sequence and an open reading frame within the unusually long leader mRNA of the accBC operon, potential stem-loop structures in the accA and accD mRNA leader regions, and a stretch of GC-rich sequences followed by AT-rich sequences common to all three promoters. In addition, both accA and accD are located in complex gene clusters. For example, the accA promoter was localized within the upstream polC gene (which encodes the DNA polymerase III catalytic subunit), suggesting that additional regulatory mechanisms exist.

Development of an RFLP linkage map in diploid peanut species.

Abstract: An RFLP linkage map of peanut has been developed for use in genetic studies and breeding programs aimed at improving the cultivated species (Arachis hypogaea L.). An F2 population derived from the interspecific hybridization of two related diploid species in the sectionArachis (A. stenosperma ×A. cardenasii) was used to construct the map. Both random genomic and cDNA clones were used to develop the framework of the map. In addition, three cDNA clones representing genes coding for enzymes involved in the lipid biosynthesis pathway have been mapped in peanut. Of the 100 genomic and 300 cDNA clones evaluated, 15 and 190, respectively, revealed polymorphisms among the parents of our mapping population. Unfortunately, a large number of these produced complex banding patterns that could not be mapped. Of the 132 markers analyzed for segregation, 117 are distributed among 11 linkage groups, while 15 have not yet been associated with any other marker. A total map distance of approximately 1063 cM has been covered to-date.

Skin in Complex Culture: The Transition from “Culture” Phenotype to Organotypic Phenotype

Abstract: A model of human skin has been developed in vitro using epidermal keratinocytes, dermal fibroblasts, and type I collagen as starting materials. The bilayered model (Testskin, LSE) consists of a contracted collagen lattice populated with dermal fibroblasts overlaid with keratinocytes that form a multilayered epidermis at the air-liquid interface. Structural, kinetic, biochemical, and functional data suggest that during cultivation the construct undergoes a gradual transition from a “culture” phenotype to an organotypic pheno-type marked by changes in keratin content, cell kinetics, corneocyte shape and size, lipid biosynthesis, morphologic organization, and function. Timing of this transition and final functional characteristics can be manipulated somewhat by culture conditions. Metabolism and biological response are similar to in vivo response at this stage. However, the organotypic culture is as yet not completely developed with respect to a fully functional stratum corneum and continuous basemen...

Insulin stimulates hepatic lipogenesis in rainbow trout, Oncorhynchus mykiss.

Abstract: The effects of the pancreatic hormones, insulin and glucagon, on rates of lipid biosynthesis in liver removed from rainbow trout, Oncorhynchus mykiss, were evaluated in vitro. Livers were removed from animals fasted for 30–36h, cut into ca. 1 mm3 pieces, and incubated in the presence of various concentrations of salmon insulin (sINS), bovine insulin (bINS), or a combination of BINS and bovine/porcine glucagon (GLU). Lipid synthesis was evaluated by total lipid concentration, 3H2O incorporation into total lipid, and by fatty acid synthetase activity. Both mammalian and sINS tended to increase tissue total lipid concentration in hepatic tissue incubated for 5h. Insulin also stimulated 3H2O incorporation into total lipid in a dose-dependent manner. Bovine INS (2 × 10−6 M) stimulated de novo synthesis nearly 6-fold over control rates; sINS (2 × 10−6 M) stimulated label incorporation more than 7-fold over control rates. Glucagon inhibited INS-stimulated 3H2O incorporation; whereas, GLU alone had no effect on lipid synthesis in liver pieces incubated 5h. Lipid class analysis indicated that bINS significantly stimulated 3H2O incorporation into phospholipids, fatty acids, and triacylglycerols. The greatest accumulation of label was in the triacylglycerol fraction, where incorporation was stimulated 17-fold over control levels. Hepatic enzymatic analysis indicated that bINS also significantly stimulated lipogenic enzyme activity 9-fold above control levels. These results indicate that INS is an important regulator of lipid synthesis in the liver of trout.

Biosynthesis and manipulation of plant products

Abstract: Starch biosynthesis A. Smith, C. Martin. Cell wall structure, utilization and manipulation G.A. Tucker, J. Mitchell. Biochemistry and molecular biology of lipid biosynthesis in plants: potential for genetic manipulation A.R. Slabas, T. Fawcett, G. Griffiths, K. Stobard.Carotenoid biosynthesis and manipulation P. Bramley, C.R.Bird, W. Schuch. Manipulating secondary metabolism in culture M.J.C. Rhodes, J.D. Hamill. Structure, function and applications of ricin and related cytotoxic proteins M.R. Hartley, J.M. Lord. Index.

Expression of the Acc1 Gene-Encoded Acetyl-Coenzyme A Carboxylase in Developing Maize (Zea mays L.) Kernels.

Abstract: A mutation (Acc1-S2) in the structural gene for maize (Zea mays L.) acetyl-coenzyme A carboxylase (ACCase) that significantly reduces sethoxydim inhibition of leaf ACCase activity was used to investigate the gene-enzyme relationship regulating ACCase activity during oil deposition in developing kernels. Mutant embryo and endosperm ACCase activities were more than 600-fold less sensitive to sethoxydim inhibition than ACCase in wild-type kernel tissues. Moreover, in vitro cultured mutant kernels developed normally in the presence of sethoxydim concentrations that inhibited wild-type kernel development. The results indicate that the Acc1-encoded ACCase accounts for the majority of ACCase activity in developing maize kernels, suggesting that Acc1-encoded ACCase functions not only during membrane biogenesis in leaves but is also the predominant form of ACCase involved in storage lipid biosynthesis in maize embryos.

Lipid Biosynthesis in Olive Cultures

Abstract: Differentiation in olive callus cultures was induced by changing the plant growth regulator content, particularly 2,4-dichlorophenoxyacetic acid, in the growth media at 25 o C. These cultures have been maintained for an extended period with low polyploid nuclei levels. Analysis of olive callus cultures indicated that the acyl lipid composition varied according to the state of differentiation and to incubation temperature. Heterotrophic olive callus was characterized by its ability to accumulate triacylglycerol rich in oleate, a situation comparable to developing olive fruit. In fact, oleate-rich triacylglycerol was enhanced in heterotrophic callus cultured at 35 o C

Research on biochemistry of herbicides : an historical overview

Abstract: Abstract Otto Warburg, the father of cellular bioenergetics, seems to have been the first investigator to report on inhibition of a plant biochemical reaction by a progenitor of a selective herbicide. The year was 1920 and the compound was phenylurethane (ethyl N-phenylcarbam ate or EPC). Warburg found that it strongly inhibited photosynthesis in Chlorella. EPC did not develop into a commercial herbicide, but the isopropyl derivatives (propham and chlorpropham) which were introduced in the late 1940s became selective herbicides. The phenylureas (monuron and diuron) were introduced in the early 1950s and shortly thereafter, interference with the Hill reaction by both phenylureas and phenylcarbamates was reported. During the latter part of the 1950s, into the 1960s, and even now, additional herbicidal chemistry was and is being announced that interferes with the Hill reaction. Duysens, in 1963, identified the site of action of diuron, i.e., on the acceptor side of PS II. Corwin Hansch, in 1966 introduced the SAR or QSAR concept in which inhibitory action of Hill inhibitors was related to various chemical and physical parameters. Because of differential responses to partial, thylakoid-associated reactions, the Hill inhibitors were subsequently divided into two groups: pure electron transport inhibitors (phenylureas, s-triazines, triazinones, and uracils) and inhibitory uncouplers (acylanilides, dinitrophenols, benzimidazoles, dinitroanilines, and benzonitriles). The inhibitory uncouplers (dinoseb-types), unlike the diuron-types, uncoupled photophosphorylation by interacting with the coupling factor complexes in both chloroplasts and intact mitochondria. Additionally, the bi-pyridyliums were shown to be reduced by PS I, hence, diverted electrons from the native acceptor. Field observations of triazine resistance were reported in 1970 and resistance was subse quently demonstrated at the thylakoid level. Application of the techniques of genetic engineering and biotechnology resulted in identification of the 32 kD a herbicide-binding protein and determination of its amino acid sequence. Crystallization and X-ray examination of the photosynthetic reaction center from Rhodopseudomonas by Michel et al. in the mid-1980s provided new models to account for interactions of herbicides with the D -1 protein. During the 1980s, herbicides were identified that interfered with biochemical machinery in chloroplasts that is not involved in electron transport and light harvesting: inhibition of lipid biosynthesis by aryloxyphenoxypropionates and cyclohexanediones, aromatic amino acid bio synthesis by glyphosate, branched chain amino acid biosynthesis by sulfonylureas and imidazolinones, carotenoid biosynthesis by pyridazinones, and porphyrin biosynthesis by diphenylethers and oxadiazoles. The current status of research in most, if not all, of the above areas was reported through oral and poster presentations at this Omiya Symposium.

Lipid biosynthesis in cultured arterial smooth muscle cells is related to their phenotype

Abstract: During the atherogenic processin vivo, arterial smooth muscle cells (SMC) undergo changes in their phenotype. In the present study, rat SMC from primary cultures and from subcultures before 10 and after 200 passages, showing contractile-like, synthetic and transformed phenotypes, respectively, were compared in regard to their lipid content and biosynthesis. The rationale for comparing these phenotypes rests in the similar changes in phenotype of SMC that occur in the formation and progression of atherosclerotic lesions. Phenotype changes were shown to be associated with changes in the phospholipid content of SMC. Phospholipid levels increased, but not as significantly as did cholesterol levels when passing from contractile to synthetic and transformed cells (1.23±0.18, 2.28±0.26 and 3.25±0.23 μg/106 cells, respectively). Cholesterol normalized in respect to cell protein was increased to the same extent. Lipid synthesis as judged by [14C]acetate incorporation was increased 3- to 12-fold in the synthetic and transformed cells, respectively, compared to contractile cells. After thin-layer chromatography, radioactivity was shown to be markedly increased in most of the lipid fractions, but label in the cholesterol fraction of synthetic and transformed cells was increased by 7- and 21-fold, respectively. Thus, SMCin vitro were shown to drastically increase cholesterol biosynthesis associated with phenotype changes. Such changes are known to occurin vivo and might represent a critical step in the deposition of excess cholesterol within foam cells.

Progress in the Cloning of Genes for Plant Storage Lipid Biosynthesis

Abstract: Functional membranes are essential for plant life, indeed for all life. Plant cells rely on glycerolipids to constitute a large proportion of these membranes. Moreover, the observation of almost exclusively 16 and 18 carbon fatty acids esterified to the glycerol backbone of glycerolipids in membranes indicates that strong functional requirements define the composition of these polar structural lipids. Many plants, however, also use neutral glycerolipid (primarily triacylglycerols, TAG) as an energy-rich storage compound. This chapter will focus on the synthesis of storage lipids in the seeds of plants although the reader will be reminded that the biosynthetic pathways for storage and structural glycerolipids largely overlap. Several recent reviews (1–3) cover plant lipid biosynthesis; however, there have been rapid advances in cloning genes encoding lipid biosynthesis enzymes since their publication.

Biochemistry and molecular biology of lipid biosynthesis in plants: potential for genetic manipulation

Abstract: Lipids are a heterogeneous class of chemicals which can be broadly defined as insoluble in water and highly soluble in non-polar organic solvents. Within this definition are included a wide range of chemical compounds including terpenes and steroids, together with a large variety of chemical compounds still waiting to have their exact structure defined. Early interest in these compounds was initiated by chemists who wished to apply their skills of separation and structural analysis to natural products. As a result there is a large volume of literature on the lipid composition of natural oils (for example Hilditch and Williams, 1964). In this review we will limit ourselves to considerations of fatty acids and esterified fatty acids.

Crystalloid smooth endoplasmic reticulum in the Quail uropygial gland

Abstract: Summary The occurrence, localization and organization of crystalloid smooth endoplasmic reticulum (SER) membrane aggregates in the male quail uropygial gland was investigated by electron microscopy. The lattice-like structures exhibiting a hexagonal honeycomb pattern are regularly found in the perinuclear region of the fully developed intermediate cell (type II) which is most effective in lipid biosynthesis and constitutes the middle layers of the stratified glandular epithelium undergoing sebaceous transformation. The crystalloids frequently exhibit a rectangular shape and tend to cluster, the latter exceeding 5 μm in length. They are composed of sets of highly ordered and densely packed tubular SER profiles. Diaminobenzidine (DAB) stained peroxisomes exhibit a close spatial relationship to the borders of crystalloids, but the organelles do not participate in the formation of these grid-like structures. The functional significance of the conformational change of the SER organization is not known. Local accumulation of specific lipogenic enzymes within this functional SER domain is discussed.

Biologie moléculaire de la biogenèse des lipides des plantes

Abstract: Summary The approaches of molecular biogenesis have been increasingly used these recent years in order to explore and to control the lipid metabolism of plants. This is linked to the important roles played by the lipid constituents in plant cells, especially at the level of membranous processes, and, also, to the biotechnological use of storage lipids. The approaches of molecular biology are used either after purification of the enzymes corresponding to steps of lipid biosynthesis—fatty acid synthase, desaturases, acyltransferases—and isolation of the corresponding genes or by complementation of mutants disturbed in one of these genes. The genes or cDNAs, coding for several key enzymes of lipid biosynthesis, recently characterized, have been used to manipulate the fatty acid composition of storage lipids, especially in rapeseed and Arabidopsis, in order to obtain oils rich in saturated fatty acids or shorter acyl chains. Fascinating perspectives related to lipid manipulation, either to improve the resista...

Lysophosphatidic Acid as a Lipid Mediator: Signal Transduction and Receptor Identification

Abstract: Phospholipids are currently attracting much interest in studies on cellular signalling and growth control. It is now well established that the breakdown products of several plasma membrane phospholipids act as signal molecules, i.e. as intracellular second messengers or as agonists that modulate cell function. Well known examples of phospholipid-derived signaling molecules include diacylglycerol, inositol trisphosphate and prostaglandins, which are all rapidly generated upon receptor stimulation. The simplest natural phospholipid, lysophosphatidic acid (LPA or monoacylglycerol-3-phosphate), is a particularly intriguing case in that it not only serves a critical precursor role in de novo lipid biosynthesis but also shows striking hormone- and growth factor-like activities when added exogenously to appropriate target cells, as if LPA binds to and thereby activates its own G-protein-coupled receptor(s). Although LPA’s lipid precursor role has been known for many decades, the possibility that this simple phospholipid may have an additional role as a signaling molecule is being appreciated only since a few years. In this chapter, we briefly summarize our recent findings on the various actions of LPA, with particular emphasis on the signal transduction pathways triggered by LPA and the identification of a candidate cell surface receptor.

Effects of Pyributicarb on Squalene Metabolism in Corn and Soybean.

Abstract: Selectivity of pyributicarb [O-3-tert-butylphenyl 6-methoxy-2-pyridyl(methyl)-thiocarbamate] and its effects on lipid biosynthesis were investigated using corn (Zea mays L. cv. Honeybantam) and soybean (Glycine max L. cv. Suzunarihakuchou) as susceptible and tolerant plants, respectively.In water culture, the elongation of young corn roots was more affected by pyributicarb than that of soybean roots.When 14C-acetate was treated with pyributicarb, both uptake into roots and incorporation into the lipid fraction were greater in soybean than in corn. Lipid biosynthesis from acetate seemed to be more active in soybean than in corn roots, and pyributicarb induced the accumulation of squalene in both types of roots. Squalene accumulation in response to the herbicide was also confirmed by gas liquid chromatography without using 14C-acetate, and was obviously larger in corn than in soybean roots.In both root types, pyributicarb decreased the total content of three major unconjugated sterols: campesterol, stigmasterol and β-sitosterol. Reduction of the sterols was considered a result of its inhibition of squalene metabolism. No clear difference was recognized, however, between soybean and corn roots in the amount of sterol reduction.There seemed to be a relation between phytotoxic activity and accumulated amount of squalene caused by the herbicide, suggesting that one action site of pyributicarb was inhibition of the squalene metabolism.

[14C]Acetate incorporation, an indicator of lipid biosynthesis within intact river biofilms

Abstract: A method is described which enables lipid biosynthesis to be determined within intact river biofilms. Significantly different rates of biosynthesis were detected in rivers of differing nutrient availability and during different seasons. Rapid changes in microbial physiology could be detected within 24 hours. The technique appeared to be well suited to investigation of factors affecting lipid biosynthesis within biofilms. Although in contrast, acetate incorporation did not correlate with microcalorimetric total activity measurements over a 12-month period, and so the method did not appear suitable for determining total metabolic activity. However, microbial lipid biosynthesis produces a valuable food resource for the ecosystems higher tropic levels and thus the acetate incorporation technique could prove useful as an indicator of aspects of aquatic ecosystem health.