中文摘要：

从海栖热袍菌克隆出编码热稳定性β-葡萄糖醛酸酶基因，以热激载体pHsh为表达质粒，在大肠杆菌中得到高效表达。基因表达产物通过一步热处理后，酶纯度达电泳均一。纯化重组酶酶学性质研究表明，β-葡萄糖醛酸酶的最适反应温度为80℃，最适反应pH为5．0，pH5．8～8．2之间酶的稳定性较好，80℃的半衰期为2h，SDS—PAGE结果显示分子量为65.9kD，与理论推算值相吻合。以对硝基苯-β-葡萄糖醛酸苷（pN/PG）为底物时，其动力学参数Km值0.18mmol／L，Vmax值为312u／mg。初步的应用分析表明，该重组酶能催化甘草酸转化为甘草次酸。

英文摘要：

The gene of β-glucuronidase from Thermotoga maritima was cloned into the plasmid pHsh, and expressed in Escherichia coli JM109. The recombinant protein was purified to homogeneity by a simple step, heat treatment. The recombinant enzyme had a molecular mass of 65.9 kD. The optimal activity of β-glucuronidase was found at pH 5.0 and 80℃. The purified enzyme was stable over a pH range from 5.8 to 8.2 and had a half life of 2 h at 80℃. The kinetic experiments at 80℃ with p-nitrophenyl-β- glucuronide as substrate gave a Km and Vmax of 0.18 mmol/L and 312 u per mg of protein. The purified enzyme could transform glycyrrhizin to glycyrrhetinic acid.