Department of Physics, Emory University, Atlanta, Georgia 30322, United States.
J Phys Chem Lett. 2023 Aug 17;14(32):7157-7164. doi: 10.1021/acs.jpclett.3c01464. Epub 2023 Aug 4.
The reactivity of individual solvent-coupled protein configurations is used to track and resolve the progress coordinate for the core reaction sequence of substrate radical rearrangement and hydrogen atom transfer in the ethanolamine ammonia-lyase (EAL) enzyme from . The first-order decay of the substrate radical intermediate is the monitored reaction. Heterogeneous confinement from sucrose hydrates in the mesophase solvent surrounding the cryotrapped protein introduces distributed kinetics in the non-native decay of the substrate radical pair capture substate, which arise from an ensemble of configurational microstates. Reaction rates increase by >10-fold across the distribution to approach that for the native enabled substate for radical rearrangement, which reacts with monotonic kinetics. The native progress coordinate thus involves a collapse of the configuration space to generate optimized reactivity. Reactivity tracking reveals fundamental features of solvent-protein-reaction configurational coupling and leads to a model that refines the ensemble paradigm of enzyme catalysis for strongly adiabatic chemical steps.
利用单个溶剂耦合蛋白构象的反应性来跟踪和解析乙醇胺氨裂解酶（EAL）中底物自由基重排和氢原子转移核心反应序列的进展坐标。监测的反应是底物自由基中间体的一级衰减。在冷冻捕获蛋白质周围的中间相溶剂中的蔗糖水合物的非均相限制在非天然的底物自由基对捕获亚基的衰减中引入了分布动力学，这是由于构象微态的集合。反应速率在整个分布中增加了 10 倍以上，接近用于自由基重排的天然使能亚基的反应速率，后者以单调动力学反应。因此，天然进展坐标涉及到构象空间的坍塌以产生优化的反应性。反应性跟踪揭示了溶剂-蛋白质-反应构象耦合的基本特征，并导致了一个模型，该模型改进了酶催化的集合范例，用于强绝热化学步骤。
