title: Purification and characterization of a beta-glucosidase with beta-xylosidase activity from Aspergillus sojae.
abstract: A beta-glucosidase (EC 3.2.1.21) was purified as an electrophoretically homogeneous protein from a solid culture of Aspergillus sojae. The molecular mass of the purified enzyme was estimated to be 250 kDa by gel filtration chromatography and 118 kDa by sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE). The isoelectric point of the enzyme was 3.80. The maximum velocity of rho-nitrophenyl beta-d-glucopyranoside degradation by the beta-glucosidase was attained at 60 degrees C and at pH 5.0. The purified enzyme was stable from pH 6.0 to 8.0, and up to 50 degrees C. The activity of the enzyme was significantly inhibited by Hg2+ and Cu2+, and stimulated by Mn2+ and Fe3+. The purified enzyme hydrolyzed beta-D-xylopyranosides as well as beta-D-glucopyranosides; the Km and Vmax values on rho-nitrophenyl beta-D-glucopyranoside were 0.14 mM and 16.7 micromol/min/mg protein, and on rho-nitrophenyl beta-D-xylopyranoside 0.51 mM and 12.2 micromol/min/mg protein, respectively.
authors.affiliation: Kagawa Prefectural Fermentation and Food Experimental Station, 1351-1 Nouma, Shouzu-gun 761-4421, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Kimura
authors.forename: N
authors.initials: N
authors.lastname: Yoshioka
authors.forename: S
authors.initials: S
authors.lastname: Tajima