cbh1重组菌的构建、产酶条件及酶特性分析
Recombinant construction,optimization and enzymatic properties analysis of cellobiohydrolase 1
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摘要: 从匍枝根霉TP-02中克隆得到cbh1的c DNA,序列测定分析表明,该基因编码526个氨基酸的蛋白质。通过DS2.5同源模拟分析,CBHI酶的活性部位是一个"桶状"的隧道结构。将cbh1基因的c DNA序列克隆到大肠杆菌表达载体p ET22b(+)中,在大肠杆菌BL21(DE3)中进行诱导表达。采用两步层析法对重组的CBHI蛋白进行纯化,对纯酶的特性进行分析。结果表明:在异丙基-β-D-硫代吡喃半乳糖苷诱导终浓度为0.5 mmol/L,诱导温度为20℃,诱导时间为14 h,经过纯化后获得比活力为3.57 IU/mg。重组酶的最适反应温度和p H分别为55℃和5.5,在p H4.56.5的范围内稳定性较好,Fe3+和Co2+对其具有较强的激活作用;以微晶纤维素为底物,Km值为6.1 mg·m L-1。Abstract: In this study,the c DNA sequence was cloned from the total RNA of the strain Rhizopus stolonifer TP-02.Sequence analysis showed that this gene encoded a polypeptide with 526 amino acids. Homology modeling was established by DS2.5 software to study cbh1 catalytic hydrolysis and the active site of CBHI was a tunnel structure of “barrel. The cbh1 c DNA sequence of the gene was inserted into expression vector p ET22b(+) and expressed in E.coli BL21(DE3). Using two-step chromatography column to purification of CBHI. Enzymatic properties of the recombinant CBHI were also investigated. Results showed that the recombinant CBHI activity could reach 3.57 IU/mg at the IPTG concentration of 0.5 mmol/L at 20 ℃ for induction 14 h. The optimum reaction temperature and p H were 55 ℃ and 5.5,and it was stable over a range of p H 4.5~6.5. Fe3+and Co2+were promoted to CBHI activity and the Kmwas 6.1 mg·m L-1with avicel.