title: Purification and characterization of an extracellular beta-xylosidase from a newly isolated Fusarium verticillioides.
abstract: An extracellular beta-xylosidase from a newly isolated Fusarium verticillioides (NRRL 26518) was purified to homogeneity from the culture supernatant by concentration by ultrafiltration using a 10,000 cut-off membrane, ammonium sulfate precipitation, DEAE Bio-Gel A agarose column chromatography and SP-Sephadex C-50 column chromatography. The purified beta-xylosidase (specific activity, 57 U/mg protein) had a molecular weight (mol. wt.) of 94,500 and an isoelectric point at pH 7.8. The optimum temperature and pH for action of the enzyme were 65 degrees C and 4.5, respectively. It hydrolyzes xylobiose 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 degrees C) and was competitively inhibited by xylose with a K(i) value of 6 mM. It did not require any metal ion for activity and stability.
authors.affiliation: Fermentation Biotechnology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Saha
mesh_terms: D001709:Biotechnology / Q000379:methods; D003470:Culture Media; D004187:Disaccharides / Q000378:metabolism; D005670:Fusarium / Q000201:enzymology* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013379:Substrate Specificity; D013696:Temperature; D014990:Xylans / Q000378:metabolism; D014995:Xylosidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004187:Disaccharides; D014990:Xylans; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase; C004173:xylobiose