Langston James A, Brown Kimberly, Xu Feng, Borch Kim, Garner Ashley, Sweeney Matt D
Novozymes, Inc., Davis, CA 95618, USA.
Biochim Biophys Acta. 2012 Jun;1824(6):802-12. doi: 10.1016/j.bbapap.2012.03.009. Epub 2012 Mar 30.
The enzyme cellobiose dehydrogenase (CDH) is of considerable interest, not only for its biotechnological applications, but also its potential biological role in lignocellulosic biomass breakdown. The enzyme catalyzes the oxidation of cellobiose and other cellodextrins, utilizing a variety of one- and two-electron acceptors, although the electron acceptor employed in nature is still unknown. In this study we show that a CDH is present in the secretome of the thermophilic ascomycete Thielavia terrestris when grown with cellulose, along with a mixture of cellulases and hemicellulases capable of breaking down lignocellulosic biomass. We report the cloning of this T. terrestris CDH gene (cbdA), its recombinant expression in Aspergillus oryzae, and purification and characterization of the T. terrestris CDH protein (TtCDH). The TtCDH shows spectral properties and enzyme activity similar to other characterized CDH enzymes. Substrate specificity was determined for a number of carbohydrate electron donors in the presence of the two-electron acceptor 2,6-dichlorophenol-indophenol. The TtCDH also shows dramatic synergy with Thermoascus aurantiacus glycoside hydrolase family 61A protein in the presence of a β-glucosidase for the cleavage of cellulose.
纤维二糖脱氢酶（CDH）不仅因其在生物技术领域的应用而备受关注，还因其在木质纤维素生物质分解中的潜在生物学作用而备受瞩目。该酶催化纤维二糖和其他纤维糊精的氧化，利用多种单电子和双电子受体，尽管自然界中使用的电子受体仍不清楚。在本研究中，我们表明，嗜热子囊菌土栖嗜热放线菌（Thielavia terrestris）在以纤维素生长时，其分泌组中存在一种CDH，同时还存在一组能够分解木质纤维素生物质的纤维素酶和半纤维素酶。我们报道了该土栖嗜热放线菌CDH基因（cbdA）的克隆、其在米曲霉（Aspergillus oryzae）中的重组表达，以及土栖嗜热放线菌CDH蛋白（TtCDH）的纯化和表征。TtCDH表现出与其他已表征的CDH酶相似的光谱特性和酶活性。在双电子受体2,6-二氯酚靛酚存在的情况下，测定了多种碳水化合物电子供体的底物特异性。在存在β-葡萄糖苷酶的情况下，TtCDH与橙色嗜热子囊菌（Thermoascus aurantiacus）糖苷水解酶家族61A蛋白在纤维素裂解方面也表现出显著的协同作用。
