Purification and characterization of a beta-D-xylosidase and an endo-xylanase from wheat flour

A beta-D-xylosidase and an endo-xylanase were purified from European wheat (Triticum aestivum) flour. The beta-D-xylosidase had a molecular weight of approximately 64,000 and an isoelectric point of 5.5. It hydrolyzed p-nitrophenyl-beta-D-xylopyranoside and xylooligosaccharides and released D-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 alpha-L-arabinofuranosidase that hydrolyzed p-nitrophenyl-alpha-L-arabinofuranoside was partially purified.