羧酸酯酶A2在大肠杆菌中的表达及特征分析

本研究采用RT-PCR法从抗性蚊虫(Culex quinquefasciatus)中克隆了羧酸酯酶A2的全长cDNA,对其进行了序列测定,并构建了融合表达质粒pET-ESTA2。转化大肠杆菌BL21后,在异丙基硫代牛乳糖苷(IPTG)的诱导下,使羧酸酯酶A2在大肠杆菌内得到表达。表达产物经亲和层析纯化获得了1条带的重组蛋白。与报道的从蚊虫体内纯化的羧酸酯酶相比,从表达产物中纯化的羧酸酯酶Km与其一致,但从表达产物纯化的羧酸酯酶的Vm比蚊虫中纯化的羧酸酯酶的Vm高。表明用亲和层析纯化的羧酸酯酶A2比从蚊虫中提取的纯度高。羧酸酯酶A2表达纯化及特征分析为其应用奠定了基础。

EXPRESSION AND CHARACTERIZATION OF CARBOXYLESTERASE A2 IN E. COLI

The most commonly observed change that has been linked to resistance development is the increase in activity of carboxylesterases. The putative mechanism involves an overproduction of this enzyme for the sequestration and the hydroxylation of various organophosphate and carbamate insecticides. Carboxylesterases A2 cDNA was amplified from Culex quinquefasciatus by RT-PCR and sequenced consequently. Target gene was inserted into pET-28a to create prokaryotic expression plasmid pET-EstA2. When pET-Es-tA2 was transformed into E. coli BL21, the recombinant was induced by IPTG. A pure recombinant protein was obtained by affinity purification. Compared with carboxylesterase A2 purified from Culex quinquefasciatus , carboxylesterase A2, purified from the product of the transgenic of E. coli, has the same Km, but the Vm was higher than that of it, which shows that carboxylesterase A2, purified from the product of E. coli by affinity, is purer than that from Culex quinquefasciatus. The study on the expression and characterization of carboxylesterase A2 in E. coli is more useful for its future application.