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  • 1
    Digitale Medien
    Digitale Medien
    Structural and genomic organization, cDNA characterization and expression analysis of the urate oxidase gene from chickpea (Cicer arietinum) (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 121 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: A complete cDNA and a genomic DNA fragment coding for urate oxidase (urate: oxygen oxidoreductase, EC 1.7.3.3) from chickpea (Cicer arietinum L.) were isolated and characterized. The 1032 bp cDNA (CAUR1) contains a complete open reading frame that encodes a 308 amino acid protein with a predicted size of 34.06 kDa and a pI of 9.38. This protein shows a strong similarity with other uricases present in the databases. Heterologous expression in Escherichia coli showed urate oxidase activity in crude extracts from induced cells, demonstrating that CAUR1 encodes a complete and functional uricase enzyme. Kinetic properties of the recombinant enzyme were similar to those of the native uricase purified from chickpea leaves. The genomic organization of the chickpea uricase gene (CAUR1) remarkably resembles that of the soybean (Glycine max L.) uricase gene, presenting eight exons and seven introns. Within the 5′-flanking region of the chickpea gene, nucleotide sequences matching consensus motifs of soybean nodule NAT2-nuclear factors and common bean (Phaseolus vulgaris L.) proteins (PNF1) are present. It demonstrates that a single copy of the uricase gene is present in the chickpea genome and that the gene is expressed not only in nodules, but also in leaves and roots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.2004.00335.x
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  • 2
    Digitale Medien
    Digitale Medien
    Isolation and characterization of xanthine dehydrogenase from Chlamydomonas reinhardtii (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Xanthine dehydrogenase (XDH, EC 1.2.1.37) of Chlamydomonas reinhardtii (Sager) 6145c wild strain has been isolated and characterized for the first time in a unicellular green alga. The enzyme has an Mr of 330 kDa, and FAD, molybdenum and iron are cofactors required for its activity as deduced from results obtained using specific inhibitors, 59Fe-labelling experiments, activity protection by FAD, physiological responses in vivo to iron and molybdenum deficiencies in the culture medium and work with mutants lacking molybdenum cofactor. Xanthine dehydrogenase exhibited Mi-chaelian kinetics typical for a bisubstrate enzyme with apparent Km values for NAD +, hypoxanthine and xanthine of 35, 160 and 70 μM, respectively. Under phototrophic conditions enzyme activity was repressed by ammonium, but xanthine was not required for the enzyme to be induced, since high levels of enzyme activity were found in cells grown on ammonium and transferred to either N-frec media or media containing either of the nitrogen sources adenine, urea, urate, xanthine, hypoxanthine and guanine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb06629.x
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  • 3
    Digitale Medien
    Digitale Medien
    Urate oxidase of Chlamydomonas reinhardii (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 62 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Urate oxidase (EC 1.7.3.3) of Chlamydomonas reinhardii cells grown on purines and purine derivatives has been partially characterized. Crude enzyme preparations have a pH optimum of 9.0, require O2 for activity, have an apparent Km of 12 μM for urate, and are inhibited by high concentrations of this substrate. Enzyme activity was particularly sensitive to metal ion chelating agents like cyanide, cupferron, diethyldithiocarbamate and o-phenanthroline, and to structural analogues of urate like hypoxanthine and xanthine. Chlamydomonas cells grow phototrophically on adenine, guanine, hypoxanthine, xanthine, urate, allantoin or allantoate as sole nitrogen source, indicating that in this alga the standard pathway of aerobic degradation of purines of higher plants, animals and many microorganisms operates. As deduced from experiments in vivo, urate oxidase from Chlamydomonas is repressed in the presence of ammonia or nitrate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04602.x
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  • 4
    Digitale Medien
    Digitale Medien
    Occurrence of an NADH diaphorase activity associated with xanthine dehydrogenase in Chlamydomonas reinhardtii (1987)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 43 (1987), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Wild-type Chlamydomonas reinhardtii cells exhibited a peculiar NADH-nitrobluetetrazolium reductase (NADH diaphorase) activity when grown under conditions in which xanthine dehydrogenase (XDH) is present. This XDH-coinduced diaphorase was electrophoretically distinguishable from constitutive diaphorases, showed the same mobility as XDH and could be assayed in vitro with dichlorophenol indophenol. Mutant strains 102, 104 and 307 of Chlamydomonas which lack XDH did not exhibit XDH-coinduced diaphorase. Heat treatment of crude extracts or partial purification of XDH inactivated or removed all constitutive diaphorases and left significant levels of XDH-coinduced diaphorase which remained always associated with XDH. These results demonstrate that XDH from C. reinhardtii, like other organisms, is also capable of catalyzing NADH oxidation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1987.tb02166.x
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  • 5
    Digitale Medien
    Digitale Medien
    Ammonium regulation of urate uptake in Chlamydomonas reinhardtii (1987)
    Springer
    Planta 171 (1987), S. 496-500 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Ammonia/ammonium ; Chlamydomonas ; Urate (uptake)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Urate was taken up at a negligible rate by Chlamydomonas reinhardtii cells grown on ammonium and transferred to media containing urate plus ammonium or urate plus chloral hydrate or cycloheximide. Addition of ammonium to cells actively consuming urate produced a rapid inhibition of urate uptake whereas the intracellular oxidation of urate was unaffected. Methylammonium but not glutamine or glutamate inhibited urate uptake. Addition of l-methionine-dl-sulfoximine to cells actively consuming urate provoked ammonium excretion, which was accompanied by a rapid inhibition of urate uptake. In cells growing on urate and exhibiting noticeable levels of nitrite-reductase activity, nitrite caused a sudden inhibition of urate uptake whereas nitrate required a time to induce nitrate reductase and to exert its inhibitory effect on uptake. The urate-uptake system did not require urate for induction since the urate-uptake capacity appeared in nitrogen-starved cells. From these results it is concluded that, in Chlamydomonas reinhardtii, ammonium inhibits urate uptake and also acts as co-repressor of the uptake system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00392297
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  • 6
    Digitale Medien
    Digitale Medien
    Characterization of urease from the phototrophic bacteriumRhodobacter capsulatus E1F1 (1993)
    Springer
    Current microbiology 27 (1993), S. 119-123 
    Details
    ISSN: 1432-0991
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Rhodobacter capsulatus E1F1 showed high cytosolic urease activity when growing on urea, purines, and purine metabolites as nitrogen source. Molecular mass ofR. capsulatus enzyme is similar to that of other bacteria and greatly differs from that of jack bean. Kinetic parameters of partially purifiedR. capsulatus enzyme resemble those described in other bacterial ureases. The activity was inhibited by metal-chelating agents and by mercurials. Urease fromR. capsulatus E1F1 was negligible in nitrogen-starved cells or in cells cultured with nitrate, ammonium, or amino acids. Moreover, ammonium inhibited both the urea uptake and the urease activity expression inR. capsulatus cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01570869
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  • 7
    Digitale Medien
    Digitale Medien
    Changes in enzyme activities involved in the degradation of 1,3-bisphosphoglycerate during erythropoiesis in rat bone marrow (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 2 (1984), S. 254-256 
    Details
    ISSN: 0263-6484
    Schlagwort(e): Bones ; 1,3-bisphosphoglycerate ; bisphosphoglycerate mutase ; erythropoiesis ; phosphoglycerate kinase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Rat bone marrow cells have been fractionated by density gradient in Percoll. Differential counting of erythroid cells, haemoglobin concentration and bisphosphoglycerate mutase and phosphoglycerate kinase activities have been determined in cellular fractions. As shown by means of a statistical approach, an increase in bisphosphoglycerate mutase activity and a slight decrease in phosphoglycerate kinase activity is found in erythroid cells as their haemoglobin content increases. Our results suggest that there is a synthesis of 2,3-bisphosphoglycerate during the erythropoietic process which parallels the synthesis of haemoglobin.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cbf.290020413
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