【摘要】 以生物合成单葡糖苷酸基甘草次酸为目的,建立了一种合成单葡糖苷酸基甘草次酸生物催化剂的筛选方法,并筛选到一株青霉菌属真菌,表达的葡糖酸苷酶具有高度底物特异性,能定向水解甘草酸生成单葡糖苷酸基甘草次酸,且研究了其酶学特质。结果表明:该催化反应的活化能Ea为116.072kJ·mol-1,反应动力学常数Km为0.328mmol·L-1,最大反应速度Vmax为3.53×10-3 mmol·L-1·min-1。催化体系的最适反应温度为50℃,最适反应pH为4.2。该催化剂在45℃以下较稳定,pH稳定性维持在4.6～5.8,Mg2+对催化活力有一定促进作用,而Cu2+、Fe2+、Fe3+、Ag+有较大抑制作用。更多还原

【Abstract】 A fungus which can biosynthesize glycyrrhetinic acid monoglucuronide(GAMG)from glycyrrhizin(GL)directionally was obtained by a self-designed biocatalyst screening method.This strain is capable of expressing glucuronidase with high substrate specificity.The investigation results of its enzymatic characteristic show that using the strain obtained,the activation energy of hydrolyzing of glucuronidase is 116.072 kJ·mol-1,maximum reaction velocity is 3.53×10-3 mmol·L-1·min-1 and Michaelis constant is 0.328 mmol·L-1.The suitable reaction temperature and pH for using the obtained strain to biosynthesize GAMG were determined as 50℃ and 4.2,respectively,and it was found that the enzyme catalyst,glucuronidase,is relatively stable under 45℃ and pH 4.6～5.8.The experiments also show that metal ion Mg2+ has activation effect,while some other cations,such as Cu2+,Fe2+,Fe3+ and Ag+,have inhibition effect on the catalytic activity of glucuronidase.更多还原