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  • 1
    Electronic Resource
    Electronic Resource
    Purification and characterization of aconitase isoforms from etiolated pumpkin cotyledons (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 88 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Although aconitase (EC 4.2.1.3) is involved in the glyoxylate cycle, which is localized in glyoxysomes, we detected very low aconitase activity in glyoxysomal fractions after sucrose gradient centrifugation of extracts prepared from etiolated pumpkin (Cucurbita sp.) colyledons. Two aconitase isoforms were purified to homogeneity, albeit in low yield, by hydrophobic interaction, hydroxylapatite and anion exchange chromatography. They were designated Aco I and Aco II; both were shown to be monomeric proteins of M1 100 000 or 98 000 by gel filtration and SDS-PAGE analysis, respectively; isoelectric points were 5.0 and 4.8, respectively. Kinetic studies revealed similarities between Aco I and Aco II. A third aconitase isoform (Aco III) was revealed but not purified to homogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01363.x
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  • 2
    Electronic Resource
    Electronic Resource
    Localisation of β-oxidation enzymes in peroxisomes of rice coleoptiles (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 76 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Enzymes of the β-oxidation pathway in rice (Oryza sativa L., cv. Arborio) coleoptiles were investigated. The coleoptiles contain acyl-CoA oxidase (EC 1.3.99.3), 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35), enoyl-CoA hydratase (EC 4.2.1.17) and thiolase (EC 2.3.1.9). Analysis of coleoptile homogenates by sucrose density fractionation showed a preferential distribution of these enzymes in the unspecialized peroxisomes. The enzymatic activity found in the mitochondrial fraction was due to peroxisomal contamination since electron micrographs show the peroxisomes to be intact and pure whereas the mitochondrial fraction was contaminated by other organelles. It appears that the β-oxidation pathway is localized in the unspecialized peroxisomes of rice coleoptiles, extending the number of plant species in which such a localization has been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb05623.x
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  • 3
    Electronic Resource
    Electronic Resource
    NADP+-isocitrate dehydrogenase in germinating cucumber cotyledons: Purification and characterization of a cytosolic isoenzyme (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The activity of NADP+-dependent isocitrate dehydrogenase (ICDH, EC 1.1.1.42) was investigated during the post-germinative growth of cucumber (Cucumis sativus L. cv. Marketmore) seedlings. Isoelectric focusing showed the presence of several isoenzymes, two of which represented 70–80% of the total NADP+-ICDH activity in cotyledons of seedlings grown in the dark. They had pI values between 4.8 and 5.8. The isoenzyme with higher pI was purified to homogeneity by hydrophobic interaction, affinity, hydroxylapatite and anion exchange chromatography. The purified isoenzyme is a dimeric protein, consisting of two apparently identical 43-kDa subunits. It is specific for NADP+, inhibited by ATP and by 2-oxoglutarate, whereas it is not inhibited by citrate, succinate, and glyoxylate. The data indicate that NADP+-ICDH from cucumber is structurally similar to ICDHs from other plants, but it shows some peculiar biochemical characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00670.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cell infrastructure and some enzyme activities in rice coleoptiles grown in air and in anoxia (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 70 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The rice (Oryza saliva L. cv. S-6) cells in anaerobic coleoptiles maintained their ultra-structure. Most of the organelles did not show significant changes as compared to those from aerobic tissues. However, the number of mitochondria was reduced by 34% and they showed enlarged cristae. Most affected were unspecialized micro-bodies: Their number was reduced by 80% under anaerobiosis and both matrix and membrane structure appeared altered. The activities of the unspecialized microbody enzymes, glycolate oxidase (EC 1.1.3.1), urate oxidase (EC 1.7.3.3) and catalase (EC 1.11.1.6) were alt reduced by anoxia. Catalase decreased to the same extent as the number of microbodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb06135.x
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  • 5
    Electronic Resource
    Electronic Resource
    Immunological analysis of aconitase in pumpkin cotyledons: the absence of aconitase in glyoxysomes (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Aconitase (EC 4.2.1.3) was purified by column chromatography and SDS-PAGE. Specific antibodies for aconitase were prepared after affinity purification of the antiserum with purified aconitase. The antibodies reacted with purified pumpkin aconitase, and with the 98 kDa protein band after electrophoretic fractionation of extracts of pumpkin cotyledons. Immunoblot analysis revealed a protein with similar molecular mass in extracts of several plants. The intensity of the 98 kDa band increased as pumpkin cotyledons developed in darkness, and decreased thereafter upon illumination. Aconitase activity showed a similar pattern. Anion exchange chromatography of a homogenate of pumpkin cotyledons, followed by western blotting, displayed the presence of immunoreactive protein bands only in fractions showing aconitase activity. The results indicate that the antibodies were specific for aconitase. When we investigated the presence of immunoreactive bands after sucrose gradient fractionation, aconitase was detected in the supernatant fractions and in mitochondria, while a very low amount was found in glyoxysomes. These data provide additional proof that aconitase is not localized in glyoxysomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb02534.x
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  • 6
    Electronic Resource
    Electronic Resource
    NADP+-isocitrate dehydrogenase in germinating and senescing pumpkin cotyledons (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: NADP+-isocitrate dehydrogenase (IDH, EC 1.1.1.42) was studied during the post-germinative growth of pumpkin (Cucurbita pepo L. cv. Alberello di Sarzana) seedlings. In cotyledons. IDH activity increased in the dark and declined after illumination. Native PAGE showed that at least two isozymes of low electrophoretic mobility are present in cotyledons and absent in other pumpkin tissues. Anion exchange chromatography performed on extracts both from 4-day-old etiolated cotyledons and from illuminated cotyledons confirmed the trend of the IDH isoforms. In senescing cotyledons an additional IDH isoform with higher electrophoretic mobility appears. Overall the data indicate the presence of specific NADP+-IDH isoforms in etiolated cotyledons and senescing cotyledons, when glyoxylate cycle enzymes are active. A possible role for these IDH isoforms is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb05322.x
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  • 7
    Electronic Resource
    Electronic Resource
    Cloning and characterization of barley long chain acyl-CoA oxidase and its possible regulation by glucose (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A barley (Hordeum vulgare L.) full-length clone coding for long chain acyl-CoA oxidase (ACX), key enzyme of β-oxidation, was isolated by cDNA library screening and 5′-rapid amplification of cDNA ends. The cDNA encodes for a polypeptide of 667 amino acids, with a molecular mass of 74.5 kDa. The amino acid sequence, beside an extensive similarity with other plant and mammalian ACXs, showed a PTS1 peroxisomal targeting signal at the C terminus and a conserved FAD-binding domain. The gene was over-expressed in E. coli and the fusion protein was shown to possess long chain acyl-CoA oxidase activity. Polyclonal antibodies were raised against a large fragment of the protein encoded by the barley putative ACX gene. Northern and Western analysis demonstrated that a basal level of long chain ACX is always present along the barley life cycle, while a higher level of expression is typical of actively growing tissues such as germinating embryos, ovary before anthesis, developing embryos, shoots and roots apexes. In vitro germination experiments with glucose and glucose analogues provided evidence about the involvement of a glucose-deriving signal in the positive modulation of ACX expression. This result highlights the role of ACX, not only during oil reserve mobilization, but also in plant growth and metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.1170103.x
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  • 8
    Electronic Resource
    Electronic Resource
    Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons (1990)
    Springer
    Planta 180 (1990), S. 435-439 
    Details
    ISSN: 1432-2048
    Keywords: Cotyledon ; Isocitrate lyase ; Leaf senescence ; Malate synthase ; Peroxisome ; Senescence (leaf, cotyledon)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Crude particulate homogenates from leaves of barley (Hordeum vulgare L.), rice (Oryza sativa L.), leaf-beet (Beta vulgaris var.cicla L.) and pumpkin (Cucurbita pepo L.) cotyledons were separated on sucrose density gradients. The peroxisomal fractions appeared at a buoyant density of 1.25 g·cm−3 and contained most of the activities of catalase (EC 1.11.1.6), and hydroxypyruvate reductase (EC 1.1.1.81) on the gradients. In peroxisomal fractions from detached leaves and green cotyledons incubated in permanent darkness we detected the presence of isocitrate lyase (EC 4.1.3.1) and malate synthase (EC 4.1.3.2), key enzymes of the glyoxylate cycle, andβ-oxidation activity (except in pumpkin). As proposed by H. Gut and P. Matile (1988, Planta176, 548–550) the glyoxylate cycle may be functional during leaf senescence, and the presence of two key enzymes indicates a transition from leaf peroxisome to glyoxysome; for pumpkin cotyledons in particular a double transition occurs (glyoxysome to leaf peroxisome during greening, and leaf peroxisome to glyoxysome during senescence).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160401
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  • 9
    Electronic Resource
    Electronic Resource
    Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons (1990)
    Springer
    Planta 180 (1990), S. 435-439 
    Details
    ISSN: 1432-2048
    Keywords: Cotyledon ; Isocitrate lyase ; Leaf senescence ; Malate synthase ; Peroxisome ; Senescence (leaf, cotyledon)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Crude particulate homogenates from leaves of barley (Hordeum vulgare L.), rice (Oryza sativa L.), leaf-beet (Beta vulgaris var. cicla L.) and pumpkin (Cucurbita pepo L.) cotyledons were separated on sucrose density gradients. The peroxisomal fractions appeared at a buoyant density of 1.25 g·cm−3 and contained most of the activities of catalase (EC 1.11.1.6), and hydroxypyruvate reductase (EC 1.1.1.81) on the gradients. In peroxisomal fractions from detached leaves and green cotyledons incubated in permanent darkness we detected the presence of isocitrate lyase (EC 4.1.3.1) and malate synthase (EC 4.1.3.2), key enzymes of the glyoxylate cycle, and β-oxidation activity (except in pumpkin). As proposed by H. Gut and P. Matile (1988, Planta 176, 548–550) the glyoxylate cycle may be functional during leaf senescence, and the presence of two key enzymes indicates a transition from leaf peroxisome to glyoxysome; for pumpkin cotyledons in particular a double transition occurs (glyoxysome to leaf peroxisome during greening, and leaf peroxisome to glyoxysome during senescence).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198797
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  • 10
    Electronic Resource
    Electronic Resource
    Peroxisomal enzyme activities in attached senescing leaves (1991)
    Springer
    Planta 184 (1991), S. 151-153 
    Details
    ISSN: 1432-2048
    Keywords: Isocitrate lyase ; Leaf senescence ; Malate synthase ; Oryza ; Peroxisome ; Senescence (natural, induced) ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recently it has been demonstrated that detached leaves show glyoxysomal enzyme activities when incubated in darkness for several days. In this report glyoxylate-cycle enzymes have been detected in leaves of rice (Oryza sativa L.) and wheat (Triticum durum L.) from either naturally senescing or dark-treated plants. Isolated peroxisomes of rice and wheat show isocitrate lyase (EC 4.1.3.1), malate synthase (EC 4.1.3.2) and β-oxidation activities. Leaf peroxisomes from dark-induced senescing leaves show glyoxylic-acid-cycle enzyme activities two to four times higher than naturally senescing leaves. The glyoxysomal activities detected in leaf peroxisomes during natural foliar senescence may represent a reverse transition of the peroxisomes into glyoxysomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208249
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