Purification and partial characterization of an endoxylanase inhibitor from barley

Hordeum vulgare L, xylanase inhibitor (HVXI), an endoxylanase inhibitor wit h a protein structure, was purified to homogeneity from barley (Hordeum vul gare L.). HVXI is a nonglycosylated monomeric protein, with a molecular wei ght of approximate to 40,000 and a pI greater than or equal to 9.3. Althoug h it inhibits different endoxylanases to a varying degree, the activities o f an alpha -L-arabinofuranosidase and a beta -D-xylosidase were not inhibit ed. Apparently, HVXI occurs in two molecular forms. These characteristics a nd 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.