Purification and Properties of β-Glucosidase from a Thermophilic Fungus Humicola lanuginosa (Griffon and Maublanc) Bunce

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An extracellular β-glucosidase (EC 3.2.1.21) has been purified to homogeneity from the culture filtrate of a thermophilic fungus, Humicola lanuginosa (Griffon and Maublanc) Bunce, using duplicating paper as the carbon source. The enzyme was purified 82-fold with a 43% yield by ion-exchange chromatography and gel filtration. The molecular weight of the protein was estimated to be 135,000 by gel filtration and 110,000 by electrophoresis. THe sedimentaiton coefficient was 10.5 S. It was an acidic protein containing high amounts of acidic amino acid residues. It was poor in sulphur-containing amino acids. It also contained 9% carbohydrate. The enzyme activity was optimum at pH 4.5 and at 60℃. The enzyme was stable in the pH range 6-9 for 24 h at 25℃. The enzyme had similar affinities towards cellobiose and p-nitrophenyl-β-D-glucoside with K_m values of 0.44 mM and 0.50 mM, respectively. THe enzyme was capable of hydrolysing larchwood xylan, xylobiose and p-nitrophenyl-β-D-xyloside, though to a lesser extent. The enzyme was specific for the β-configuration and glucose moiety in the substrate.
公益社団法人日本生物工学会の論文
1989-06-25