Khalili Ghadikolaei Kamran, Akbari Noghabi Kambiz, Shahbani Zahiri Hossein
Department of Energy and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran.
Appl Microbiol Biotechnol. 2017 Sep;101(18):6929-6939. doi: 10.1007/s00253-017-8430-2. Epub 2017 Aug 1.
The camel rumen metagenome is an untapped source of glycoside hydrolases. In this study, novel genes encoding for a modular xylanase (XylC) and a cellulase (CelC) were isolated from a camel rumen metagenome and expressed in Escherichia coli BL21 (DE3). XylC with xylanase (Xyn), CBM, and carbohydrate esterase (CE) domains was characterized as a β-1,4-endoxylanase with remarkable catalytic activity on oat-spelt xylan (K = 2919 ± 57 s). The implication of XylC's modular structure in its high catalytic activity was analyzed by truncation and fusion construction with CelC. The resulting fusions including Cel-CBM, Cel-CBM-CE, and Xyn-CBM-Cel showed remarkable enhancement in CMCase activity with K values of 742 ± 12, 1289 ± 34.5, and 2799 ± 51 s compared to CelC with a K of 422 ± 3.5 s. It was also shown that the bifunctional Xyn-CBM-Cel with synergistic xylanase/cellulase activities was more efficient than XylC and CelC in hydrolysis of rice and barley straws.
骆驼瘤胃宏基因组是糖苷水解酶的一个未开发来源。在本研究中，从骆驼瘤胃宏基因组中分离出编码模块化木聚糖酶（XylC）和纤维素酶（CelC）的新基因，并在大肠杆菌BL21（DE3）中表达。具有木聚糖酶（Xyn）、碳水化合物结合模块（CBM）和碳水化合物酯酶（CE）结构域的XylC被鉴定为一种β-1,4-内切木聚糖酶，对燕麦-斯佩尔特木聚糖具有显著的催化活性（K = 2919 ± 57 s）。通过与CelC进行截短和融合构建，分析了XylC模块化结构对其高催化活性的影响。与K为422 ± 3.5 s的CelC相比，所得融合蛋白Cel-CBM、Cel-CBM-CE和Xyn-CBM-Cel的羧甲基纤维素酶（CMCase）活性显著增强，K值分别为742 ± 12、1289 ± 34.5和2799 ± 51 s。还表明，具有协同木聚糖酶/纤维素酶活性的双功能Xyn-CBM-Cel在水稻和大麦秸秆水解中比XylC和CelC更有效。
