title: Purification and properties of an extracellular beta-xylosidase from a newly isolated Fusarium proliferatum.
abstract: An extracellular beta-xylosidase from a newly isolated Fusarium proliferatum (NRRL 26517) capable of utilizing corn fiber xylan as growth substrate was purified to homogeneity from the culture supernatant by DEAE-Sepharose CL-6B batch adsorption chromatography, CM Bio-Gel A column chromatography, Bio-Gel A-0.5 m gel filtration and Bio-Gel HTP Hydroxyapatite column chromatography. The purified beta-xylosidase (specific activity, 53 U/mg protein) had a molecular weight of 91,200 as estimated by SDS-PAGE. The optimum temperature and pH for the action of the enzyme were 60 degrees C and 4.5, respectively. The purified enzyme hydrolyzed xylobiose and higher xylooligosaccharides but was inactive against xylan substrates. It had a Km value of 0.77 mM (p-nitrophenol-beta-D-xyloside, pH 4.5, 50 degrees C) and was competitively inhibited by xylose with a Ki value of 5 mM. The enzyme did not require any metal ion for activity and stability. Comparative properties of this enzyme with other fungal beta-xylosidases are presented.
authors.affiliation: Fermentation Biotechnology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, US Department of Agriculture, Peoria, IL 61604, USA. sahabc@ncaur.usda.gov
authors.forename: Badal C
authors.initials: BC
authors.lastname: Saha
mesh_terms: D004187:Disaccharides / Q000737:chemistry; D004789:Enzyme Activation; D004795:Enzyme Stability; D005670:Fusarium / Q000737:chemistry / Q000145:classification / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D013045:Species Specificity; D013379:Substrate Specificity; D013696:Temperature; D014995:Xylosidases / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification*
chemical_list: D004187:Disaccharides; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase; C004173:xylobiose