We had investigated the enzymatic hydrolysis of soybean saponins and selected soybean saponin hydrolase from Aspergillus oryzae KO-2. We attempted purification of this enzyme for further characterization. This enzyme was purified 1500-fold using ammonium sulfate fractionation and Sephadex G-200 gel filtrations. The enzyme was electrophoretically homogeneous and a glycoprotein by PAS staining. By gel filtration, the molecular weight of enzyme was 158,000 and SDS-PAGE showed the enzyme to have a tetrameric structure composed of heterogeneous subunits of 35,000 and 45,000. The enzyme activity was stable at temperatures below 40 degrees C and stable from pH 5.0 to 8.0. The optimum pH was pH 4.5 to 5.0 and the optimum temperature was 50 degrees C. The Km and Vmax for soyasaponin I were 0.48 mM and 9.8 mumol/hr mg protein, respectively. After hydrolysis with the enzyme, soyasapogenol B and alpha-L-rhamnopyranosyl (1----2)-beta-D-galactopyranosyl (1----2)-D-glucuronopyranoside were released from soyasaponin I.

No abstract

We had investigated the enzymatic hydrolysis of soybean saponins and selected soybean saponin hydrolase from Aspergillus oryzae KO-2. We attempted purification of this enzyme for further characterization. This enzyme was purified 1500-fold using ammonium sulfate fractionation and Sephadex G-200 gel filtrations. The enzyme was electrophoretically homogeneous and a glycoprotein by PAS staining. By gel filtration, the molecular weight of enzyme was 158,000 and SDS-PAGE showed the enzyme to have a tetrameric structure composed of heterogeneous subunits of 35,000 and 45,000. The enzyme activity was stable at temperatures below 40 degrees C and stable from pH 5.0 to 8.0. The optimum pH was pH 4.5 to 5.0 and the optimum temperature was 50 degrees C. The Km and Vmax for soyasaponin I were 0.48 mM and 9.8 mumol/hr mg protein, respectively. After hydrolysis with the enzyme, soyasapogenol B and alpha-L-rhamnopyranosyl (1----2)-beta-D-galactopyranosyl (1----2)-D-glucuronopyranoside were released from soyasaponin I.

No abstract

Soyasaponin I-V, A1-A3, and acetylsoyasaponin A1-A61~8) were reported as the constituents of soybean saponins. They have a common structure of linking glucuronic acid at the C-3 site of soyasapogenol. It has been reported that soybean saponins have some physiological activities9' 10) and also undesirable bitter and astringent tastes.11} While soybean saponins are therefore likely to contribute to undesirable tastes in soybean-derived foods, Iijima et al.ll) have reported that the