Characterization and mode of action of xylanases ␁and some accessory enzymes

F.J.M. Kormelink

    Research output: Thesisinternal PhD, WU

    Abstract

    <p>Three endo-(l,4)-β-D-xylanases; (Endo I, Endo II, and Endo III), a (1,4)-β-xylosidase and an (1,4)-β-D-arabinoxylan arabinofuranohydrolase (AXH) were purified from a culture filtrate produced by <em>Aspergillus awamori</em> CMI 142717. In addition to these enzymes, an acetyl xylan esterase (AE) was purified from a culture filtrate produced by <em>Aspergillus niger</em> DS 16813.<p>The enzymes were characterized by determining specific activities, molecular weight, isoelectric point, kinetic parameters (K <sub><font size="-2">m</font></sub> ,V <sub><font size="-2">max</font></sub> ), optimum pH and optimum temperature.<p>Arabinoxylan oligosaccharides were derived from alkali-extracted wheat arabinoxylans by complete digestion with Endo I and III. The structures of unknown oligosaccharides were elucidated by <sup><font size="-2">1</font></SUP>H-n.m.r. spectroscopy. From these structures a model was proposed for the mode of action of Endo I and Endo III towards arabinoxylans. The same oligosaccharides were also used to specify the action of (1,4)-β-xylosidase, AXH and two α-L-arabinofuranosidases towards these arabinofuranosylated arabinoxylan oligosaccharides.<p>The interaction between the purified enzymes was studied by degradation of xylans from rice bran, oat spelt, wheat-flour, larchwood, and birchwood by single and combined actions of these enzymes on these substrates. The cooperativity was monitored by the amount of reducing sugars and by the types of products released.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Voragen, A.G.J., Promotor, External person
    Award date9 Dec 1992
    Place of PublicationS.l.
    Publisher
    Print ISBNs9789054850526
    Publication statusPublished - 1992

    Keywords

    • glycosidases

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