title: Purification and characterization of xylanases from Aspergillus giganteus.
abstract: A strain of Aspergillus giganteus cultivated in a medium with xylan produced two xylanases (xylanase I and II) which were purified to homogeneity. Their molar mass, estimated by SDS-PAGE, were 21 and 24 kDa, respectively. Both enzymes are glycoproteins with 50 degrees C temperature optimum; optimum pH was 6.0-6.5 for xylanase I and 6.0 for xylanase II. At 50 degrees C xylanase I exhibited higher thermostability than xylanase II. Hg2+, Cu2+ and SDS were strong inhibitors, 1,4-dithiothreitol stimulated the reaction of both enzymes. Both xylanases are xylan-specific; kinetic parameters indicated higher efficiency in the hydrolysis of oat spelts xylan. In hydrolysis of this substrate, xylotriose, xylotetraose and larger xylooligosaccharides were released and hence the enzymes were classified as endoxylanases.
authors.affiliation: Departamento de Bioquímica e Microbiologia, Instituto de Biociências, UNESP, 13506-900, Rio Claro, São Paulo, Brazil.
authors.forename: M B
authors.initials: MB
authors.lastname: Fialho
authors.forename: E C
authors.initials: EC
authors.lastname: Carmona
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry; D001230:Aspergillus / Q000201:enzymology* / Q000254:growth & development; D002850:Chromatography, Gel; D003300:Copper / Q000032:analysis / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry; D003911:Dextrans; D004229:Dithiothreitol; D004591:Electrophoresis, Polyacrylamide Gel; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D020536:Enzyme Activators / Q000032:analysis / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000032:analysis / Q000494:pharmacology; D004795:Enzyme Stability; D005590:Fractional Precipitation; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017669:Mercury Compounds / Q000032:analysis / Q000494:pharmacology; D008970:Molecular Weight; D012967:Sodium Dodecyl Sulfate; D013379:Substrate Specificity; D013696:Temperature; D014990:Xylans / Q000378:metabolism
chemical_list: D003470:Culture Media; D003911:Dextrans; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D006023:Glycoproteins; D017669:Mercury Compounds; D014990:Xylans; D012967:Sodium Dodecyl Sulfate; D003300:Copper; C025614:sephadex; D043364:Endo-1,4-beta Xylanases; D000645:Ammonium Sulfate; D004229:Dithiothreitol