- Partial hydrolysis of soyasaponin I and the hepatoprotective effects of the hydrolytic products. Study of the structure-hepatoprotective relationship of soyasapogenol B analogs
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As a part of our studies of hepatoprotective drugs, we prepared some soyasapogenol B analogs from soyasaponin I. We examined the hepatoprotective effects of these analogs, using immunologically-induced liver injury, in primary cultured rat hepatocytes. Soyasaponin III and soyasapogenol B monoglucuronide were more effective than soyasaponin I. Both compounds were significantly effective even at 30μM. The action of soyasapogenol B was almost equal to that of soyasaponin I, although glucuronic acid did not show any activity even at the highest dose (500μM). When the two compounds were mixed, the hepatoprotective action did not change, compared with soyasapogenol B. Therefore, we concluded that the linkage between glucuronic acid and soyasapogenol B could enhance the hepatoprotective activity.
- Ikeda, Tsuyoshi,Udayama, Manabu,Okawa, Masafumi,Arao, Tomonori,Kinjo, Junei,Nohara, Toshihiro
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- Purification and some properties of soybean saponin hydrolase from Aspergillus oryzae KO-2.
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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.
- Kudou,Tsuizaki,Uchida,Okubo
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