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  • Digitale Medien  (5)
  • 1995-1999  (5)
  • 1905-1909
  • 1830-1839
  • arable soil  (3)
  • Cyclodextrinase  (2)
Materialart
  • Digitale Medien  (5)
Erscheinungszeitraum
  • 1995-1999  (5)
  • 1905-1909
  • 1830-1839
Jahr
  • 1
    ISSN: 1432-072X
    Schlagwort(e): Cyclodextrin metabolism ; Klebsiella oxytoca ; Cyclodextrinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract It has been shown previously that the products of 11 genes are required for metabolism of starch byKlebsiella oxytoca via a novel pathway. An extracellular cyclodextrin glucanotransferase first degrades starch into α-and β-cyclodextrins; evidence then has been presented that the cyclodextrins are transported into the cytoplasma via a specific system and that they are metabolised inside the cell. To provide support for this model, we have analysed whetherKlebsiella oxytoca possesses a cytoplasmic enzyme able to linearise cyclodextrins. A possible candidate was the product of thecymH gene since it displays sequence similarity with cyclodextrinases from other organisms. ThecymH gene was overexpressed, and the CymH protein was purified. CymH is a monomer of 69 kDa molecular mass and hydrolysed cyclodextrins at an optimum pH of 7.0 and an optimum temperature of 23° C, respectively. The apparentK m increased with increasing size of the cyclodextrins, but the reaction velocity decreased. Linear malto-oligosaccharides were also accepted as substrates, but were hydrolysed with a lower efficiency. Final products in each case were maltose and maltotriose. It was demonstrated by immunoblotting that CymH is located in the cytoplasm and that no signal peptide was cleaved off. SincecymH mutants were no longer able to grow on cyclodextrins, these results prove that cyclodextrins are degraded inside the cell, and they support the contention of the existence of a specific transport system.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-072X
    Schlagwort(e): Key words Cyclodextrin metabolism ; Klebsiella ; oxytoca ; Cyclodextrinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract It has been shown previously that the products of 11 genes are required for metabolism of starch by Klebsiella oxytoca via a novel pathway. An extracellular cyclodextrin glucanotransferase first degrades starch into α- and β-cyclodextrins; evidence then has been presented that the cyclodextrins are transported into the cytoplasma via a specific system and that they are metabolised inside the cell. To provide support for this model, we have analysed whether Klebsiella oxytoca possesses a cytoplasmic enzyme able to linearise cyclodextrins. A possible candidate was the product of the cymH gene since it displays sequence similarity with cyclodextrinases from other organisms. The cymH gene was overexpressed, and the CymH protein was purified. CymH is a monomer of 69 kDa molecular mass and hydrolysed cyclodextrins at an optimum pH of 7.0 and an optimum temperature of 23° C, respectively. The apparent K m increased with increasing size of the cyclodextrins, but the reaction velocity decreased. Linear malto-oligosaccharides were also accepted as substrates, but were hydrolysed with a lower efficiency. Final products in each case were maltose and maltotriose. It was demonstrated by immunoblotting that CymH is located in the cytoplasm and that no signal peptide was cleaved off. Since cymH mutants were no longer able to grow on cyclodextrins, these results prove that cyclodextrins are degraded inside the cell, and they support the contention of the existence of a specific transport system.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 181 (1996), S. 185-192 
    ISSN: 1573-5036
    Schlagwort(e): arable soil ; cover box technique ; nitrous oxide ; spatial and temporal variability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Five soil cover box systems varying in area were used to measure the N2O emissions from four arable soils. The covered area of the systems ranged from 78 to 576000 cm2. The observed N2O emission rates were approximately log-normal distributed. The greatest influence of variation of N2O emission rates could be attributed to the factor sampling date/time. The different soil cover box systems were assessed by comparing measured mean N2O releases, their time courses and spatial variation. The spatial coefficient of variation of N2O emission rates decreased logarithmically with an increasing radius of the soil cover box system used.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 170 (1995), S. 287-295 
    ISSN: 1573-5036
    Schlagwort(e): arable soil ; crop rotation ; freeze-thaw ; microbial biomass-C ; plant growth ; substrate-induced respiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Sugar beet, winter wheat and winter barley were planted within a crop rotation on an arable soil with conventional soil management. Soil samples were taken monthly from different depths of the whole plough layer (0–10, 10–20 and 20–30 cm) during a 56 month period. The samples were analysed for microbial biomass carbon using the substrate-induced respiration technique. Temporal changes in the amount of microbial biomass carbon were observed. Within a year, microbial biomass-C varied from low values (−15% of total mean) in winter to high values (+15% of total mean) in summer. Relative deviations from the annual means were calculated for each month in the year to demonstrate these fluctuations. Temporal changes in microbial biomass-C depended on the sources of sample variation (5 years, 3 crops, 3 sampling depths). The highest relative deviation from the annual mean microbial biomass-C was attributable to the factor “year”. Less variations were caused by “crops” and “sampling depth”. Soil microbial biomass-C remained constant during frost periods. From the observed temporal changes, recommendations for a suitable date for soil sampling are given, which allows a representative estimation of the mean annual microbial biomass-C content in arable soils.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 181 (1996), S. 57-63 
    ISSN: 1573-5036
    Schlagwort(e): arable soil ; nitrous oxide ; soil texture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract N2O-loss rates from two soils were measured over a continuous observation period of 2 years. The two soils, differing in texture (sandy loam and silty loam), are frequently used for intensive crop production. Rates were estimated using a closed soil cover box technique. N2O-losses obtained were scrutinised with physical, chemical and microbiological properties of the soils as well as with climatic data. Large temporal changes in N2O-emission rates were found. The data were approximately log-normal distributed. In spring maximal values of 20 g N2O-N ha-1 d-1 were observed. According to this observation, two situations associated with high flux rates could be distinguished; 1. N2O- production by soil at spring thaw and 2. N2O-production within one week after N-fertilizer application. For both soils equal N2O-losses were found, which are adequate to 1 kg N2O-N ha-1 per year. From this data was calculated that N2O-losses ranged from 0.8–1.5% of the applied fertilizer N.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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