Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
Bioresour Technol. 2011 Feb;102(4):3973-6. doi: 10.1016/j.biortech.2010.11.114. Epub 2010 Nov 29.
A β-glucosidase from Clostridium cellulovorans (CcBG) was fused with one of three different types of cellulases from Clostridium thermocellum, including a cellulosomal endoglucanase CelD (CtCD), a cellulosomal exoglucanase CBHA (CtCA) and a non-cellulosomal endoglucanase Cel9I (CtC9I). Six bifunctional enzymes were constructed with either β-glucosidase or cellulase in the upstream. CtCD-CcBG showed the favorable specific activities on phosphoric acid swollen cellulose (PASC), an amorphous cellulose, with more glucose production (2 folds) and less cellobiose accumulation (3 folds) when compared with mixture of the single enzymes. Moreover, CtCD-CcBG had significantly improved thermal stability with a melting temperature (T(m)) of 10.9°C higher than that of CcBG (54.5°C) based on the CD unfolding experiments. This bifunctional enzyme is thus useful in industrial application to convert cellulose to glucose.
来自纤维梭菌（Clostridium cellulovorans）的β-葡萄糖苷酶（CcBG）与三种不同类型的来自嗜热纤维梭菌（Clostridium thermocellum）的纤维素酶融合，包括纤维小体内切葡聚糖酶 CelD（CtCD）、纤维小体外切葡聚糖酶 CBHA（CtCA）和非纤维小体内切葡聚糖酶 Cel9I（CtC9I）。在上下游构建了六个具有β-葡萄糖苷酶或纤维素酶的双功能酶。与单酶混合物相比，CtCD-CcBG 在磷酸膨胀纤维素（PASC）上具有更好的比活性，对无定形纤维素的葡萄糖产量更高（2 倍），细胞二糖积累更少（3 倍）。此外，基于 CD 展开实验，CtCD-CcBG 的热稳定性显著提高，熔点（T(m)）比 CcBG（54.5°C）高 10.9°C。因此，这种双功能酶在将纤维素转化为葡萄糖的工业应用中很有用。
