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 w heat (Triticum aestivum) flour. The beta-D-xylosidase had a molecular weight of approximately 64,000 and an isoelectric point of 5.5. It hyd rolyzed p-nitrophenyl-beta-D-xylopyranoside and xylooligosaccharides a nd released D-xylose units from wheat arabinoxylan and oat spelts xyla n. An endo-xylanase with a molecular weight of approximately 55,000 wa s also obtained and it consisted of a number of isoforms with isoelect ric points between 4.0 and 5.0. The action of the isolated endo-xylana se depended on the degree of substitution of the polysaccharide. Unbra nched polymers were preferentially hydrolyzed. Since xylo-oligosacchar ides were not hydrolyzed, the enzyme appeared to need at least five or more consecutive unsubstituted xylose units. Finally, an alpha-L-arab inofuranosidase that hydrolyzed p-nitrophenyl-alpha-L-arabinofuranosid e was partially purified.