Polymer Program, Institute of Material Science, §Department of Chemistry, and ∥Department of Molecular and Cellular Biology, University of Connecticut , Storrs, Connecticut 06269, United States.
ACS Appl Mater Interfaces. 2013 Sep 11;5(17):8486-94. doi: 10.1021/am401916k. Epub 2013 Aug 22.
The formation of polycatalytic enzyme complexes may enhance the effectiveness of enzymes due to improved substrate interaction and synergistic actions of multiple enzymes in proximity. Much effort has been made to develop highly efficient polycatalytic cellulase complexes by immobilizing cellulases on low-cost polymer or nanoparticle scaffolds, aiming at their potential applications in biomass conversion to fuels. However, some key cellulases carry out the hydrolytic reaction on crystalline cellulose in a directional, processive manner. A large, artificial polycatalytic complex is unlikely to undergo a highly coordinated motion to slide on the cellulose surface as a whole unit. The mechanism underlying the activity enhancements observed in some artificial cellulase complexes and the limit of this approach remain elusive. Herein, we report the synthesis of polycatalytic cellulase complexes bound to colloidal polymer nanoparticles with a magnetic core and describe their unique adsorption, hydrolytic activities, and motions on cellulose. The polycatalytic clusters of cellulases on colloidal polymers show an increased rate of hydrolytic reactions on cellulose, but this was observed mainly at relatively low cellulase-to-cellulose ratios. Enhanced efficiency is mainly attributed to increased local concentrations of cellulases on the scaffolds and their polyvalent interactions with cellulose. However, once bound, the polycatalytic complexes can only carry out reactions locally and are not capable of relocating to new sites rapidly due to their lack of long-range surface mobility and their extremely tight binding. The development of highly optimized polycatalytic complexes may arise by developing novel nanoscaffolds that induce concerted motion of the complex as a whole.
多酶复合物的形成可以通过提高酶与底物的相互作用和多个酶在邻近区域的协同作用来提高酶的效率。人们已经做出了很大的努力，通过将纤维素酶固定在低成本的聚合物或纳米颗粒支架上来开发高效的多酶纤维素复合酶，旨在将其潜在应用于生物质转化为燃料。然而，一些关键的纤维素酶以定向、连续的方式对结晶纤维素进行水解反应。大型的人工多酶复合物不太可能像整体单元那样进行高度协调的运动来在纤维素表面上滑动。在一些人工纤维素复合酶中观察到的活性增强的机制以及这种方法的局限性仍然难以捉摸。在此，我们报道了与具有磁性核的胶体聚合物纳米颗粒结合的多酶纤维素复合酶的合成，并描述了它们在纤维素上的独特吸附、水解活性和运动。胶体聚合物上的多酶纤维素簇在纤维素上显示出水解反应速率的提高，但主要是在相对较低的纤维素酶与纤维素的比例下观察到的。效率的提高主要归因于支架上纤维素酶的局部浓度增加及其与纤维素的多价相互作用。然而，一旦结合，多酶复合物由于缺乏长程表面迁移性和极其紧密的结合，只能在局部进行反应，而不能迅速重新定位到新的位置。通过开发诱导复合物整体协调运动的新型纳米支架，可能会出现高度优化的多酶复合物的发展。
