Functional importance of Asp37 from a family 11 xylanase in the binding to two proteinaceous xylanase inhibitors from wheat

Authors

  • Tariq A. Tahir,

    1. Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK
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  • Anne Durand,

    1. Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK
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    • 1

      John Innes Center, Norwich Research Park, Norwich NR4 7UH, UK.

  • Kurt Gebruers,

    1. Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3000 Leuven, Belgium
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  • Alain Roussel,

    1. Architecture et Fonction de Macromolécules Biologiques (AFMB), UMR-6098, CNRS et Universités d'Aix-Marseille I et II, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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  • Gary Williamson,

    1. Nestlé Research Center, P.O. Box 44, CH-1000 Lausanne 26, Switzerland
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  • Nathalie Juge

    Corresponding author
    1. Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK
    2. Institut Méditerranéen de Recherche en Nutrition, UMR INRA 1111, Faculté des Sciences de St Jérôme, Av. Escadrille Normandie-Niemen, Marseilles, F-13397 Cedex 20, France
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*Corresponding author. Tel.: +44 1603 255068; fax: +44 1603 255038, E-mail address: nathalie.juge@bbsrc.ac.uk

Abstract

Aspergillus niger xylanase is a target enzyme of the two wheat proteinaceous inhibitors, XIP-I and TAXI-I. We previously suggested that the xylanase “thumb” region was XIP-I binding site. Here, we expressed the Asp37Ala mutant in Pichia pastoris and showed that the mutation abolished the enzyme capacity to interact with both inhibitors, suggesting a direct contact at the active site. The mutant pH profile was altered, confirming the key role of Asp37 in determining the pH optima of glycoside hydrolase family 11. The results are consistent with a competitive inhibition mode and underline the strategic importance of Asp37 in the inhibition mechanism.

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