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  • fatty acid synthesis  (5)
  • Glycoprotein (immunolocalisation)  (1)
  • 1
    ISSN: 1432-2048
    Keywords: Cell wall (glycoprotein) ; Elicitor ; Glycoprotein (immunolocalisation) ; Hydroxyproline ; Phaseolus (cell wall) ; Stress (pathogen induced)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A major wall protein of suspension-cultured cells of French bean has been isolated and characterised. It can be prepared from walls or the culture filtrate and in composition it is particularly rich in proline, valine and glutamic acid/glutamine and contains appreciable amounts of hydroxyproline. The N-terminus shows some glycosylation, while following chemical deglycosylation the first 38 residues were found to be identical to those of proline-rich proteins from soybean. However, the composition of the highly purified Mr-42000 bean protein differs considerably from the soybean proteins and must contain its own specific domains. An antibody was raised and used to demonstrate the inducibility of the Mr-42000 bean protein in response to elicitor action. The protein was found to be mainly localised in the intercellular spaces of the cortical cells of bean hypocotyls and at the wall-plasmalemma interface of xylem vessels, another potentially accessible compartment for pathogens. Following wounding, the protein was found to be generally distributed in the wall of epidermal and cortical cells of the hypocotyls. The Mr-42000 protein is cross reactive with antibodies raised to glycoproteins of the Rhizobium infection thread and the chitin-binding hydroxyproline-rich glycoprotein, potato lectin. These common epitopes together with the previously demonstrated chitin-binding properties of the bean protein indicate a role in host-microbial interactions. Furthermore, the Mr-42000 protein itself bound to the growing hyphal tips of the bean pathogen, Colletotrichum lindemuthianum.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: acetoacetyl-(acyl carrier protein) ; acyl carrier protein ; acetyl CoA:ACP transacylase ; fatty acid synthesis ; condensation reaction ; avocado ; Persea americana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract β-ketoacyl-ACP synthetase III (KAS III) has been purified from avocado using a six-step purification procedure. The enzyme, which is cerulenin-insensitive and thiolactomycin-sensitive, was assayed using a partial component reaction: acetyl CoA:ACP transacylase (ACAT) activity. KAS III activity is distinguished from ACAT activity on the basis that the former is highly stimulated by the addition of malonyl CoA in the presence of malonyl-CoA:ACP transacylase, and the latter is not. KAS III and ACAT activity have been separated from each other thus providing the first evidence that these two discrete activities exist in higher plants. Both of these enzymes have been implicated in the initial reactions of fatty acid synthesis. KAS III was purified 134-fold using a combination of PEG precipitation, Fast Q, ammonium sulphate precipitation, Phenyl Sepharose and ACP-affinity chromatography. The enzyme requires Triton X-100 for solubility and is highly salt sensitive. The subunit molecular mass of 37 kDa has been identified by SDS-PAGE. The results of gel filtration analysis are consistent with the native enzyme being homodimeric. The native molecular mass of KAS III is 69 kDa and that of ACAT 18.5 kDa. The enzyme has a pH optimum of 7.0–7.5, which is similar to the pH optimum of the ACAT reaction. The Km for acetyl CoA is 12.5 μM and the Km for malonyl-ACP is 14μM. Both KAS III and ACAT are sensitive to thiolactomycin inhibition. The results are discussed with respect to the potential role of acetyl CoA:ACP transacylase in plants.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5028
    Keywords: acyl-(acyl carrier protein) thioesterase ; acyl carrier protein ; Brassica napus ; fatty acid synthesis ; rape ; seed development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The level of two thioesterases, acyl-CoA thioesterase and acyl-ACP thioesterase was determined during seed maturation in oil seed rape. Both thioesterase activities rose markedly prior to the onset of lipid accumulation, but the induction kinetics suggest that the activities reside on distinct polypeptides. Acyl-ACP thioesterase (EC 3.1.2.14) was purified 2000-fold using a combination of ion exchange, ACP-affinity chromatogr aphy, chromatofocusing and gel filtration. Using native gel electrophoresis, and assays for enzymic activity, two polypeptides were identified on SDS-PAGE as associated with the activity. Cleveland mapping of these polypeptides, of 38 kDa component and 33 kDa respectively, demonstrated that they are related. An antibody was prepared against the 38 kDa component, and this also recognises the 33 kDa polypeptide in highly purified preparations. Western blotting of a crude extract identifies one band at 38 kDa consistent with the 33 kDa component being a degradation product generated during purification. The native molecule has a Mr of 70 kDa indicating a dimeric structure. The enzyme has a pH optimum of 9.5 and shows strong preference for oleoyl-ACP as substrate. The intact enzyme has an N-terminus blocked to protein sequencing. We also found that two other polypeptides co-purify with acyl-ACP thioesterase under native conditions. The N-terminal amino-acid sequence of these polypeptides is shown and their possible identity is discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 19 (1992), S. 169-191 
    ISSN: 1573-5028
    Keywords: Oil seed rape ; lipids ; fatty acid synthesis ; biotechnology ; desaturases ; mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5028
    Keywords: acyl ; Brassica napus ; fatty acid synthesis ; plastidial location ; seed ; thioesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acyl-ACP thioesterases are involved in regulating chain termination of fatty acid biosynthesis in plant systems. Previously, acyl-ACP thioesterase purified from Brassica napus seed tissue has been shown to have a high preference for hydrolysing oleoyl-ACP. Here, oligonucleotides derived from B. napus oleoyl-ACP thioesterase protein sequence data have been used to isolate two acyl-ACP thioesterase clones from a B. napus embryo cDNA library. The two clones, pNL2 and pNL3, contain 1642 bp and 1523 bp respectively and differ in the length of their 3′ non-coding regions. Both cDNAs contain open reading frames of 366 amino acids which encode for 42 kDa polypeptides. Mature rape thioesterase has an apparent molecular weight of 38 kDa on SDS-PAGE and these cDNAs therefore encode for precursor forms of the enzyme. This latter finding is consistent with the expected plastidial location of fatty acid synthase enzymes. Northern blot analysis shows thioesterase mRNA size to be ca. 1.6 kb and for the thioesterase genes to be highly expressed in seed tissue coincident with the most active phase of storage lipid synthesis. There is some sequence heterogeneity between the two cDNA clones, but overall they are highly homologous sharing 95.7% identity at the DNA level and 98.4% identity at the amino acid level. Some sequence heterogeneity was also observed between the deduced and directly determined thioesterase protein sequences. Consistent with the observed sequence heterogeneity was Southern blot data showing B. napus thioesterase to be encoded by a small multi-gene family.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-9368
    Keywords: fatty acid synthesis ; oil seed rape ; seed expressed ; developmentally regulated ; thioesterase II ; transgenic seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Medium chain hydrolase (MCH) is an enzyme which regulates the chain length of fatty acid synthesis specifically in the mammary gland of the rat. During lactation, MCH interacts with fatty acid synthase (FAS) to cause premature release of acyl chains, thus providing medium chain fatty acids for synthesis of milk fat. In this study we have investigated the ability of rat MCH to interact with the phylogenetically more distant FAS structure present in plant systems and to cause a perturbation of fatty acid synthesis. Inin vitro experiments, addition of purified MCH to rapeseed homogenates was found to cause a significant perturbation of fatty acid synthesis towards medium chain length products. The rat MCH gene was expressed in transgenic oilseed rape using a seed specific rape acyl carrier protein (ACP) promoter and a rape ACP plastid targeting sequence. Western analysis showed MCH protein to be present in transgenic seed and for its expression to be developmentally regulated in concert with storage lipid synthesis. The chimaeric preprotein was correctly processed and immunogold labelling studies confirmed MCH to be localized within plastid organelles. However, fatty acid analysis of oil from MCH-expressing rape seed showed no significant differences to that from control seed.
    Type of Medium: Electronic Resource
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