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A p-o-xylosidase and an endo-xylanase were purified from European wheat (Trificum aesfivum) flour. The p-o-xylosidase had a molecular weight of approximately 64,000 and an isoelectric point of 5.5. It hydrolyzed pnitrophenyl-Eo-xylopyranoside and xylooligosaccharides and released o-xylose units from wheat arabinoxylan and oat spelts xylan. An endo-xylanase with a molecular weight of approximately 55,000 was also obtained and it consisted of a number of isoforms with isoelectric points between 4.0 and 5.0. The action of the isolated endo-xylanase depended on the degree of substitution of the polysaccharide. Unbranched polymers were preferentially hydrolyzed. Since xylo-oligosaccharides were not hydrolyzed, the enzyme appeared to need at least five or more consecutive unsubstituted xylose units. Finally, an a-L-arabinofuranosidase that hydrolyzed pnitrophenyl-a-L-arabinofuranoside was partially purified.

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An endogenous wheat (Triticum aestivum) flour endoxylanase was purified t o homogeneity from a crude wheat flour extract by ammonium sulfate precipitation and cation-exchange chromatography. The 30-kD protein had an isoelectric point of 9.3 or higher. A sequence of 19 amino acids at the NH, terminus showed 84.2% identity with an interna1 sequence of the 15-kD grain-softness protein, friabilin. High-performance anion-exchange chromatography and gel-permeation analysis of the hydrolysis products indicated the preferential hydrolysis of highly branched structures by the enzyme; wheat arabinoxylan and rye (Secale cereale) arabinoxylan (high arabinose to xylose ratios) were hydrolyzed more efficiently by this enzyme than oat (Avena safiva) spelt xylan (low arabinose to xylose ratios). The release of the hydrolysis products as a function of time suggested that the endoxylanolytic activity was associated with the release of arabinose units from the polysaccharides, suggesting that the enzyme action i s similar to that by endoxylanases from Ceratocystis paradoxa, Aspergillus niger, and Neurospora crassa. Although the enzyme released arabinose from arabinoxylan, it did not hydrolyze pnitrophenyl-a-i-arabinofuranoside. From the above, it follows that the enzyme, called arabinoxylanase, differs from most microbial endoxylanases and from an endoxylanase purified earlier from wheat flour.AX, the main NSP in wheat (Triticum uestivum) endosperm, consists of a linear backbone of 1P-linked 6-Dxylopyranose units with L-arabinofuranosyl residues attached to the main chain by 1,3-and/or 1,2-cu-glycosidic linkages. Its structure was recently intensively studied using 'H-NMR spectroscopy and methylation analysis (Hoffmann et al., 1991(Hoffmann et al., , 1992a(Hoffmann et al., , 1992bGruppen, 1992aGruppen, , 1992bGruppen, , 1993Cleemput et al., 1993Cleemput et al., , 1995a.NSP-hydrolyzing enzymes are found in wheat grain (Preece and MacDougall, 1958;Kulp, 1968;Lee and Ronalds, 1972;Schmitz et al., 1974;Bremen, 1981; Adlung, 1985;Moore and Hoseney, 1990), in germinated wheat and wheat bran (Beldman et al., 1996), in barley (Hordeum vulgure) aleurone layers (Taiz and Honigman, 1976;Dashek