Purification and Partial Characterization of an Endoxylanase Inhibitor from Barley

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.