两种菌产皂苷糖苷酶的性质比较

对微生物Absidiasp.D0d菌产的薯蓣皂苷糖苷酶(RhaD)和微生物Absidiasp.A3r菌产的黄芪皂苷糖苷酶(RhaA)进行了分离纯化,并对它们的酶性质做了比较。RhaD的分子质量是59 ku,最适反应pH是5.0,pH稳定范围是3.0~8.0;最适反应温度是40℃,在60℃以下稳定。金属离子Na+、K+对酶反应基本没有影响,Mg2+、Zn2+、Ca2+、Cu2+、Fe3+对酶反应有抑制作用。酶反应动力学参数Km为19.26 mmol/L,Vmax为1.23 mmol/(L.h)。RhaA的分子质量是54 ku,最适反应pH是5.0,pH稳定范围是3.0~6.0;最适反应温度是40℃,在60℃以下稳定,Mg2+和Ca2+对RhaA的酶反应没有影响,Fe3+、Cu2+的抑制作用较为明显。酶反应动力学参数Km为17.86 mmol/L,Vmax为1.18 mmol/(L.h)。RhaD只能水解与穿山龙薯蓣皂苷母环结构相似的异螺甾烷醇型的皂苷上的α-鼠李糖,不能水解pNP--αL-Rha。RhaA仅水解四环三萜环阿屯烷型的黄芪皂苷16上的α-鼠李糖,不能水解pNP--αL-Rha。

Comparison of twoglycosidase from Absidia sp.

Dioscin-glycosidase(RhaD) from Absidia sp.D0d and Astragaloside glycosidase(RhaA) from Absidia sp.A3r was purified.The molecular mass of RhaD was 59 ku.The optimum pH and temperature of RhaD for enzyme activity was 5.0 and 40 ℃ respectively.RhaD was stable at pH 3.0-8.0 and below 60 ℃.K+ and Na+ showed no effect on the enzyme activity,while Mg2+,Zn2+,Ca2+,Cu2+,Fe3+ inhibited the enzyme.The Km and Vmax were 19.26 mmol/L and 1.23 mmol/(L·h).The molecular mass of RhaA was 54 ku.The optimum pH and temperature of RhaA for enzyme activity was 5.0 and 40 ℃ respectively.RhaA was stable at 3.0-6.0,and below 60 ℃.Mg2+ and Ca2+ showed no effect on the enzyme activity,while Cu2+ and Fe3+ inhibited the enzyme.The Km and Vmax were 17.86 mmol/L and 1.18 mmol/(L·h).RhaD can hydrolyze α-rhamnoside of Dioscin but not pNP-α-L-Rha.RhaA can hydrolyze α-rhamnoside of Astragaloside16 but not pNP-α-L-Rha.