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Purification and Partial Characterization of an Endoxylanase Inhibitor from Barley

¹Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium. ²Corresponding author. Phone: (+32)-16-321634. Fax: (+32)-16-321997. E-mail: hans.goesaert@agr.kuleuven.ac.be ³Laboratory of Molecular Immunology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.

Hordeum vulgare L. xylanase inhibitor (HVXI), an endoxylanase inhibitor with a protein structure, was purified to homogeneity from barley (Hordeum vulgare L.). HVXI is a nonglycosylated monomeric protein, with a molecular weight of ≈40,000 and a pI ≥ 9.3. Although it inhibits different endoxylanases to a varying degree, the activities of an α-L-arabinofuranosidase and a β-D-xylosidase were not inhibited. Apparently, HVXI occurs in two molecular forms. These characteristics and the N-terminal sequences of the composing polypeptides show that HVXI is homologous with Triticum aestivum L. xylanase inhibitor I, an endoxylanase inhibitor from wheat flour.