Purification and characterization of an extracellular beta-xylosidase froma newly isolated Fusarium verticillioides

An extracellular beta -xylosidase from a newly isolated Fusarium verticilli oides (NRRL 26518) was purified to homogeneity from the culture supernatant by concentration by ultrafiltration using a 10,000 cut-off membrane, ammon ium sulfate precipitation, DEAE Bio-Gel A agarose column chromatography and SP-Sephadex C-50 column chromatography. The purified beta -xylosidase (spe cific activity, 57 U/mg protein) had a molecular weight (mol. wt.) of 94,50 0 and an isoelectric point at pH 7.8. The optimum temperature and pH for ac tion of the enzyme were 65 degreesC and 4.5, respectively. It hydrolyzes xy lobiose and higher xylooligosaccharides but is inactive against xylan. The purified,beta -xylosidase had a K-m value of 0.85 mM (p-nitrophenol-beta -D -xyloside, pH 4.5, 50 degreesC) and was competitively inhibited by xylose w ith a K-i value of 6 mM. It did not require any metal ion for activity and stability.