Purification and Characterization of β-Glucosidase from Agaricus bisporus (White Button Mushroom)

β-Glucosidase (β-D-glucoside glucohydrolase, EC 3.2.1.21) is a catalytic enzyme present in both prokaryotes and eukaryotes that selectively catalyzes either the linkage between two glycone residues or between glycone and aryl or alkyl aglycone residue. Growing edible mushrooms in the soil with increased cellulose content can lead to the production of glucose, which is a process dependent on β-glucosidase. In this study, β-glucosidase was isolated from Agaricus bisporus (white button mushroom) using ammonium sulfate precipitation and hydrophobic interaction chromatography, giving 10.12-fold purification. Biochemical properties of the enzyme were investigated and complete characterization was performed. The enzyme is a dimer with two subunits of approximately 46 and 62 kDa. Optimum pH for the enzyme is 4.0, while the optimum temperature is 55 °C. The enzyme was found to be exceptionally thermostable. The most suitable commercial substrate for this enzyme is p-NPGlu with Km and Vmax values of 1.751 mM and 833 U/mg, respectively. Enzyme was inhibited in a competitive manner by both glucose and δ-gluconolactone with IC50 values of 19.185 and 0.39 mM, respectively and Ki values of 9.402 mM and 7.2 µM, respectively. Heavy metal ions that were found to inhibit β-glucosidase activity are I(-), Zn(2+), Fe(3+), Ag(+), and Cu(2+). This is the first study giving complete biochemical characterization of A. bisporus β-glucosidase.