Showing papers by "John L. Harwood published in 2000"

Handbook of olive oil

Abstract: Handbook of olive oil : , Handbook of olive oil : , کتابخانه مرکزی دانشگاه علوم پزشکی ایران

Novel inhibitors of the condensing enzymes of the type II fatty acid synthase of pea (Pisum sativum)

Abstract: The type II fatty acid synthases (FASs) of higher plants (and Escherichia coli) contain three condensing enzymes called beta-ketoacyl-ACP synthases (KAS), where ACP is acyl-carrier-protein. We have used novel derivatives of the antibiotic thiolactomycin to inhibit these enzymes. Overall de novo fatty acid biosynthesis was measured using [1-(14)C]acetate substrate and chloroplast preparations from pea leaves, and [1-(14)C]laurate was used to distinguish between the effects of the inhibitors on KAS I from those on KAS II. In addition, the activities of these enzymes, together with the short-chain condensing enzyme, KAS III, were measured directly. Six analogues were tested and two, both with extended hydrocarbon side chains, were found to be more effective inhibitors than thiolactomycin. Incubations with chloroplasts and direct assay of the individual condensing enzymes showed that all three compounds inhibited the pea FAS condensing enzymes in the order KAS II > KAS I > KAS III. These results demonstrate the general activity of thiolactomycin and its derivatives against these FAS condensation reactions, and suggest that such compounds will be useful for further detailed studies of inhibition and for use as pharmaceuticals against Type II FASs of pathogens.

Purification and characterisation of acyl-CoA: glycerol 3-phosphate acyltransferase from oil palm (Elaeis guineensis) tissues.

Abstract: Glycerol 3-phosphate acyltransferase (GPAT, EC 2.3.15) catalyses the first step of the Kennedy pathway for acyl lipid formation. This enzyme was studied using high-speed particulate fractions from oil palm (Elaeis guineensis Jacq.) tissue cultures and mesocarp acetone powders. The fractions were incubated with [14C]glycerol 3-phosphate and incorporation of radioactivity into Kennedy pathway intermediates studied. Optimal conditions were broadly similar between the two preparations but those from fruit mesocarp clearly contained more active enzymes for the subsequent stages of the Kennedy pathway – as exemplified by the appreciable accumulation of radioactivity in triacylglycerol. Experiments with different acyl-CoA substrates showed that the GPAT in both high-speed particulate preparations had a significant preference for palmitate. Glycerol 3-phosphate acyltransferase was solubilised from both preparations with optimal solubilisation being achieved at 0.5% (w/v) CHAPS concentrations. Solubilised GPATs were purified further using DE52 ion-exchange chromatography and Sephadex G-100 molecular exclusion chromatography. Purifications of up to about 70-fold were achieved. The purified GPATs showed a strong preference for palmitoyl-CoA compared to other acyl-CoA donors, in keeping with the importance of palmitate in palm oil.

Microbial degradation of the plant sulpholipid.

Abstract: Five bacterial strains capable of using sulphoquinovose (6-deoxy-6-sulpho-D-glucopyranose) as a sole source of carbon have been isolated and partially characterized.

Characterization of lipoxygenase isoforms in olive callus cultures.

Abstract: Lipoxygenase activity is critical for the development of flavours and aromas in olive oils. We have partly purified isoforms of molecular mass 95 kDa that have activity against linoleic or alpha-linolenic acids by a simple procedure from olive callus cultures.

Lipid Biosynthesis in Olives

Abstract: Olive fruits, as do most oil crops, accumulate lipid in the form of different molecular species of triacylglycerols. Therefore, in discussing the biosynthesis of olive oil, one must consider, first, how the acyl chains are produced and, second, how these acyl chains are assembled onto the glycerol backbone.

Effect of copper and lead on lipid metabolism in bryophytes and lichens.

Abstract: Bryophytes and lichens have a widespread occurrence and can survive under extreme environmental conditions, such as drought, low temperatures, continuous light or prolonged darkness. It has been shown that lipid metabolism is sensitive to both metal response and metal resistance mechanisms in many organisms, including yeast, Silene cucubalus and in the marine brown algae Fucus spp. and Ascophyllum nodosum. In the present study, the effects of lead and copper on lipid metabolism have been studied in two moss species, Rhytidiadelphus squarrosus and Dicranum scoparium and also in the lichen Peltigera horizontalis with a cyanobacterial Nostoc photobiont.

The inhibition of fatty acid elongation by pebulate can be effectively counteracted by the safener dichlormid.

Abstract: The thiocarbamate herbicide pebulate inhibits fatty acid elongation, which is necessary for surface lipid biosynthesis. As both barley and wild oats are susceptible to pebulate, the safener dichlormid was used to study the reversal of its herbicidal effect. Fatty acid elongation was restored by a dichlormid pretreatment in barley, but not in pebulate-expressed oats.

Pea choline kinase: purification, properties and isolation of a cDNA.

Abstract: Choline kinase has been partially purified from pea seedlings and its properties studied. Using sequence information from soya bean and other choline kinases, we have also isolated a cDNA encoding the enzyme. It encodes a protein of 343 amino acids (calculated molecular mass of 39785 Da), which shows 82% homology with the soya bean choline kinase. The protein has been expressed in Eschericiha coli with very good activity and high expression levels.

Use of Tissue Cultures as Model Systems for the Study of Lipid Biochemistry in Olives

Abstract: Plant tissue technology was established, more or less, by Haberladt (see Yeoman & Aitchinson 1973) at the beginning of the twentieth century. He attempted to capitalize on the regenerative ability of higher plants in order to reproduce complete plants. The next major advancement was almost four decades later when callus tissue from tobacco and carrot was cultured successfully for extended periods (see Dodds & Roberts 1985). From these modest beginnings, plant tissue technology has developed to its present state. In fact, the term tissue culture actually might be a misnomer because, under in vitro conditions, cells often grow as an amorphous mass and exhibit little or no tissue morphology. With the discovery of kinetin (Miller et al. 1955) and the subsequent classic experiments by Skoog and Miller (1957), the role of plant growth regulators in plant growth and development has been clearly elucidated. Since then, the use of such plant growth regulators has greatly facilitated the maintenance of cells in culture while, at the same time, preserving their totipotency.

Recent advances in the biochemistry of plant lipids : proceedings of the 14th International Symposium on Plant Lipids held in Cardiff, U.K., in July 2000

Abstract: The proceedings of the 14th International Symposium on Plant Lipids covers the full range of biochemical, chemical and molecular biological aspects of plant lipids (including lipid structure and analysis, fatty acid biosynthesis, lipid metabolism and oxidation, isoprenoids and steroids, signalling, environmental aspects and biotechnolgy). The book contains over 200 papers divided into the following sections: fatty acid synthesis: from CO2 to functional genomics; lipid analysis fatty acid biosynthesis; complex lipid biosynthesis; lipid catabolism; sterols and isoprenoids; lipids and signalling; environmental effects on lipids; and biotechnological aspects.

Morphological and metabolic changes in transgenic wheat with altered glycerol-3-phosphate acyltransferase or acyl-acyl carrier protein (ACP) thioesterase activities.

Abstract: We have transformed varieties of wheat with a Pisum sativum glycerol-3-phosphate acyltransferase gene, and also with an Arabidopsis thaliana acyl-ACP thioesterase gene. Morphological (growth, organelle development) and metabolic changes (fatty acid labelling of chloroplast and non-chloroplast lipids) have been observed in transgenics with altered gene expression for either enzyme.