title: Purification of thermostable α-galactosidase from Irpex lacteus and its use for hydrolysis of oligosaccharides.
abstract: A monomeric α-galactosidase (ILGI) from the mushroom Irpex lacteus was purified 94.19-fold to electrophoretic homogeneity. ILGI exhibited a specific activity of 18.36 U mg(-1) and demonstrated a molecular mass of 60 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). ILGI was optimally active at 80 °C and pH 5.0, and it was stable over a temperature range of 4-70 °C and a wide pH range of 2.0-12.0. ILGI was completely inactivated by Ag(+) and Hg(2+) ions and N-bromosuccinimide (NBS). Moreover, ILGI exhibited good resistance to proteases. Galactose acted as a noncompetitive inhibitor with Ki and Kis of 3.34 and 0.29 mM, respectively. The α-galactosidase presented a broad substrate specificity, which included p-nitrophenyl α-D-galactopyranoside (pNPGal), melibiose, stachyose, and raffinose with Km values of 1.27, 3.24, 7.1, and 22.12 mM, correspondingly. ILGI exhibited efficient and complete hydrolysis to raffinose and stachyose. The aforementioned features of this enzyme suggest its potential value in food and feed industries.
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing, P.R. China.
authors.forename: Yajie
authors.initials: Y
authors.lastname: Guo
authors.affiliation: School of Public Health, Peking University, Beijing, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: Beijing key Laboratory of Biodiversity and Organic Farming, College of Resources and Environmental Sciences, China Agricultural University, Beijing, P.R. China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Shao
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing, P.R. China.
authors.forename: Hexiang
authors.initials: H
authors.lastname: Wang
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing, P.R. China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Song
mesh_terms: D001487:Basidiomycota / Q000201:enzymology* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005690:Galactose / Q000378:metabolism*; D006868:Hydrolysis; D009844:Oligosaccharides / Q000378:metabolism*; D013025:Glycine max / Q000382:microbiology; D013379:Substrate Specificity; D000519:alpha-Galactosidase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D009844:Oligosaccharides; D000519:alpha-Galactosidase; D005690:Galactose
keywords: Characterization; Irpex lacteus; Purification; α-Galactosidase