title: Isolation and characterization of a thermostable beta-xylosidase in the thermophilic bacterium Geobacillus pallidus.
abstract: The isolation, purification, biochemical and biophysical characterization of the first reported beta-xylosidase from Geobacillus pallidus are described. The protein has an optimum pH close to 8 and an optimum temperature of 70 degrees C. These biochemical properties agree with those obtained by spectroscopic techniques, namely, circular dichroism (CD), infrared (FTIR) and fluorescence measurements. Thermal denaturation, followed by CD and FTIR, showed an apparent thermal denaturation midpoint close to 80 degrees C. The protein was probably a hydrated trimer in solution with, an elongated shape, as shown by gel filtration experiments. FTIR deconvolution spectra indicated that the protein contains a high percentage of alpha-helix (44%) and beta-sheet (40%). The sequencing of the N terminus and the biochemical features indicate that this new member of beta-xylosidases belongs to the GH52 family. Since there are no reported structural studies of any member of this family, our studies provide the first clue for the full conformational characterization of this protein family.
authors.affiliation: Departamento de Biología, Facultad Experimental de Ciencias y Tecnología, Universidad de Carabobo, Valencia, Venezuela.
authors.forename: Denny
authors.initials: D
authors.lastname: Quintero
authors.forename: Zoraida
authors.initials: Z
authors.lastname: Velasco
authors.forename: Estefanía
authors.initials: E
authors.lastname: Hurtado-Gómez
authors.forename: José L
authors.initials: JL
authors.lastname: Neira
authors.forename: Lellys M
authors.initials: LM
authors.lastname: Contreras
mesh_terms: D001406:Bacillaceae / Q000201:enzymology*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013379:Substrate Specificity; D014995:Xylosidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase