纤维素外切酶CelC7的异源表达及降解黄原胶性能

Heterologous expression and xanthan-degradation properties of cellulase exonuclease CelC7

为开发新型黄原胶外切酶、获得聚合度高度集中的黄原胶活性寡糖,对来自牛瘤胃真菌的纤维素酶CelC7的编码基因进行全基因合成,并在大肠杆菌中进行异源表达。该基因大小为1032 bp,编码344个氨基酸残基,表达蛋白产物理论分子质量为40 ku,属于糖苷水解酶GH7家族。该酶在大肠杆菌中高效可溶性表达,经过Ni-NTA亲和层析纯化后,可得到纯度达90%的纯酶。酶学性质分析结果表明,该酶最适反应温度为50℃,最适pH为6.0。CelC7能够有效地对黄原胶主链进行特异性切割,将其水解为低分子质量寡糖。亚铁离子螯合活性实验结果显示,该低分子质量寡糖对亚铁离子螯合活性的半清除活性IC50为3.60 mg/mL,表明成功制备黄原胶活性寡糖。

To develop a new exoxanthanase and obtain xanthan oligosaccharides with high degree of polymerization,the coding gene of cellulase CelC7 from bovine rumen fungi was synthesized and heterologously expressed in Escherichia coli.The gene is 1032 bp in size and encodes 344 amino acid residues.The theoretical molecular weight of CelC7 is 40 ku,belonging to the GH7 family of glycoside hydrolases.The enzyme was highly soluble in E.coli.The enzyme was obtained with a purity of 90%by Ni-NTA affinity chromatography.The analysis of enzymatic properties showed that the optimal reaction temperature was 50℃and the optimal pH was 6.0.CelC7 can effectively cut the main chain of xanthan specifically and hydrolyze it into low molecular weight oligosaccharides.The results of ferrous ion chelating activity showed that the semi scavenging activity IC 50 of the low molecular weight oligosaccharide for ferrous ion chelating activity was 3.60 mg/mL,indicating that the active xanthan oligosaccharide was successfully prepared.