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  • 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
    BibTip Andere fanden auch interessant ...
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