title: A novel thermostable alpha-galactosidase from the thermophilic fungus Thermomyces lanuginosus CBS 395.62/b: purification and characterization.
abstract: High levels of an extracellular alpha-galactosidase are produced by the thermophilic fungus Thermomyces lanuginosus CBS 395.62/b when grown in submerse culture and induced by sucrose. The enzyme was purified 114-fold from the culture supernatant by (NH(4))(2)SO(4) fractionation, and by chromatographical steps including Sepharose CL-6B gel filtration, DEAE-Sepharose FF anion-exchange, Q-Sepharose FF anion-exchange and Superose 12 gel filtration. The purified enzyme exhibits apparent homogeneity as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and iso-electric focusing (IEF). The native molecular weight of the monomeric alpha-galactosidase is 93 kDa with an isoelectric point of 3.9. The enzyme displays a pH and temperature optimum of 5-5.5 and 65 degrees C, respectively. The purified enzyme retains more than 90% of its activity at 45 degrees C in a pH range from 5.5 to 9.0. The enzyme proves to be a glycoprotein and its carbohydrate content is 5.3%. Kinetic parameters were determined for the substrates p-nitrophenyl-alpha-galactopyranoside, raffinose and stachyose and very similar K(m) values of 1.13 mM, 1.61 mM and 1.17 mM were found. Mn(++) ions activates enzyme activity, whereas inhibitory effects can be observed with Ca(++), Zn(++) and Hg(++). Five min incubation at 65 degrees with 10 mM Ag(+) results in complete inactivation of the purified alpha-galactosidase. Amino acid sequence alignment of N-terminal sequence data allows the alpha-galactosidase from Thermomyces lanuginosus to be classified in glycosyl hydrolase family 36.
authors.affiliation: Department of Brewing and Distilling, Faculty of Food Science, Corvinus University of Budapest, H-1118 Budapest, Ménesi út 45, Hungary. judit.szabo@uni-corvinus.hu
authors.forename: Judit M
authors.initials: JM
authors.lastname: Rezessy-Szabó
authors.forename: Quang D
authors.initials: QD
authors.lastname: Nguyen
authors.forename: Agoston
authors.initials: A
authors.lastname: Hoschke
authors.forename: Christophe
authors.initials: C
authors.lastname: Braet
authors.forename: Gyöngyi
authors.initials: G
authors.lastname: Hajós
authors.forename: Marc
authors.initials: M
authors.lastname: Claeyssens
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000201:enzymology*; D002384:Catalysis; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D013696:Temperature; D000519:alpha-Galactosidase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000519:alpha-Galactosidase