中文摘要：

从 thermophilic 细菌 Geobacillus sp 编码 carboxylesterase 的基因(741 bp ) 。ZHl 被克隆并且在 Escherichia coli 的 overexpressed。净化的 recombinant 蛋白质由 SDS 页分析介绍了大约 40 kDa 的一个分子的团。当底层证实了它的 esterase 活动，用有不同的酰的 p-nitrophenyl 酉旨的酶试金锁住长度，产出有 p-nitrophenyl 醋酸盐的最高特定的活动。在测试的 p-nitrophenyl 酉旨之中， carboxylesterase 更高效地为 p-nitrophenyl caprylate，而是 hydrolyzed p-nitrophenyl 丁酸盐介绍了偏爱。当 p-nitrophenyl 丁酸盐被用作底层时， recombinant carboxylesterase 在 pH 展出了最高的活动 8.0 和 60 瑡潩 ? 景挠汨牯灯票汬愠 ? 桃 ??? 慳楬楮祴 ? 楤獳汯敶 ? 湩牯慧楮 ? 楮牴杯湥 ???? 楤獳汯敶 ? 硯杹湥 ? 佄 ? 湡 ? 楳楬慣整 ? 楓 ?? 慷 ? 敲灳湯楳汢? 潦 ? 桴 ? 慶楲瑡潩獮椠 ? 潺灯慬歮潴 ? 潣浭湵瑩 ? 瑳畲瑣牵 ? 湩琠敨匠湡敭 ? 慂吗？

英文摘要：

The gene （741 bp） encoding carboxylesterase from the thermophilic bacterium Geobacillus sp. ZH1 was cloned and overexpressed in Escherichia coll. The purified recombinant protein presented a molecular mass of about 40 kDa by SDS-PAGE analysis. Enzyme assays using p-nitrophenyl esters with different acyl chain lengths as the substrates confirmed its esterase activity, yielding highest specific activity with p-nitrophenyl acetate. Among the p-nitrophenyl esters tested, the carboxylesterase presented preference for p-nitrophenyl caprylate, but hydrolyzed p-nitrophenyl butyrate more efficiently. When p-nitrophenyl butyrate was used as a substrate, the recombinant carboxylesterase exhibited highest activity at pH 8.0 and 60℃. Almost no decrease in esterase activity was observed at 60℃ for 3 h, and over 40% of activity was still maintained after incubation at 90℃ for 3 h. These results indicate that Geobacillus sp. ZH1 recombinant esterase was thermostable. The enzymatic activity was inhibited by the addition of phenylmethylsulfonyl fluoride, indicating that it contains serine residue, which plays a key role in the catalytic mechanism. Except SDS and xylene, this esterase showed stability toward other tested detergents and organic solvents. Cloning, expression, and biochemical characterization of Geobacillus sp. ZH1 carboxylesterase lay a good foundation for its structural characterization and industrial application.