Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Khlong Luang, Pathum Thani 12120, Thailand.
Bioresour Technol. 2015 Jan;176:129-35. doi: 10.1016/j.biortech.2014.11.042. Epub 2014 Nov 15.
Expansins are non-catalytic proteins which loosen plant cell wall structure. In this study, binding kinetics and synergistic action of five bacterial expansins on cellulosic and hemicellulosic polysaccharides were studied. The expansins differed in binding capacity (Bmax) and affinity (Kd) for different substrates. A common pattern of binding efficiency (Bmax/Kd) was found among the expansins tested, in which efficiency was greatest for the phosphoric acid-swollen cellulose (PASC), then the hemicellulose arabinoxylan followed by the microcrystalline cellulose (Avicel PH101). The expansins enhanced the action of Trichoderma reesei cellulase/hemicellulase mixture for degrading all three substrates to varying degrees. Among the substrates and expansins tested, BpEX from Bacillus pumilus and CmEX from Clavibacter michiganensis showed the greatest enhancement effect on arabinoxylan with 11.4 and 12.2-fold greater reducing sugar yield than the reaction with enzyme alone. The work gives insights into the wider application of expansins on enhancing polysaccharide hydrolysis, particularly on hemicellulosic substrates.
扩展蛋白是一种非催化蛋白，可松弛植物细胞壁结构。在这项研究中，研究了五种细菌扩展蛋白对纤维素和半纤维素多糖的结合动力学和协同作用。扩展蛋白对不同底物的结合能力（Bmax）和亲和力（Kd）存在差异。在测试的扩展蛋白中发现了一种常见的结合效率（Bmax/Kd）模式，其中效率最高的是磷酸膨胀纤维素（PASC），其次是半纤维素阿拉伯木聚糖，然后是微晶纤维素（Avicel PH101）。扩展蛋白增强了里氏木霉纤维素酶/半纤维素酶混合物对所有三种底物的降解作用，在不同程度上提高了降解效率。在所测试的底物和扩展蛋白中，来自芽孢杆菌的 BpEX 和来自密歇根棒状杆菌的 CmEX 对半木聚糖的增强效果最大，与单独使用酶的反应相比，还原糖产量分别增加了 11.4 倍和 12.2 倍。这项工作深入了解了扩展蛋白在增强多糖水解方面的更广泛应用，特别是对半纤维素底物的应用。
