title: Purification and properties of a thermostable extracellular beta-D-xylosidase produced by a thermotolerant Aspergillus phoenicis.
abstract: A beta-D-xylosidase was purified from cultures of a thermotolerant strain of Aspergillus phoenicis grown on xylan at 45 degrees C. The enzyme was purified to homogeneity by chromatography on DEAE-cellulose and Sephadex G-100. The purified enzyme was a monomer of molecular mass 132 kDa by gel filtration and SDS-PAGE. Treatment with endoglycosidase H resulted in a protein with a molecular mass of 104 kDa. The enzyme was a glycoprotein with 43.5% carbohydrate content and exhibited a pl of 3.7. Optima of temperature and pH were 75 degrees C and 4.0-4.5, respectively. The activity was stable at 60 degrees C and had a Km of 2.36 mM for p-nitrophenyl-beta-D-xylopiranoside. The enzyme did not exhibit xylanase, cellulase, galactosidase or arabinosidase activities. The purified enzyme was active against natural substrates, such as xylobiose and xylotriose.
authors: Departamento de Bioquímica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil.
authors: A C
authors: AC
authors: Rizzatti
authors: J A
authors: JA
authors: Jorge
authors: H F
authors: HF
authors: Terenzi
authors: C G
authors: CG
authors: Rechia
authors: M L
authors: ML
authors: Polizeli
mesh_terms: D001230:Aspergillus / Q000201:enzymology* / Q000254:growth & development; D003470:Culture Media; D004795:Enzyme Stability; D007700:Kinetics; D013379:Substrate Specificity; D013696:Temperature; D014995:Xylosidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D003470:Culture Media; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase