Atomic resolution experimental interrogation of hydride quantum tunnelling in enzyme reaction chemistry

酶是一种非凡的催化剂，与非催化反应相比，可加速反应高达10^21。在所有生物中，这些酶是特殊的蛋白质分子，催化生化反应，执行特定的生物功能。多年来，化学家和生物化学家都试图利用酶系统的这种催化潜力来加速自然界中通常不会发生的反应。酶作为“设计者”催化剂的开发需要对酶作用的物理化学有深入和定量的了解。为了了解酶催化威力的来源，人们开发了酶催化的定量物理模型--最新的结合了量子现象(如隧道效应)的模型，以解释酶对速率的加速。利用X射线结晶学和核磁共振光谱学等结构生物学方法阐明了生物催化剂的原子结构，进一步加强了这一点。这就定义了酶的“结构决定功能”范式，以及生物催化可以由底物分子(或其高能态)和蛋白质之间的互补作用驱动的概念。尽管取得了这些进展，但我们对生物催化的理解是非常不完整的，我们无法使用目前的物理模型来解释酶的催化能力的几个数量级。最近的一个焦点是蛋白质运动或动力学在驱动生物催化中的作用。这调用了一种灵活的酶催化剂，当与底物复合时，可以在各种不同的时间尺度(亚皮秒到几秒)内探索无数不同的结构状态。酶的催化能力与蛋白质的动态性质有关，但结构生物学方法只能提供催化剂的“静态”描述，或者充其量提供在催化中可能重要或可能不重要的时间平均结构集合。该领域面临的主要挑战是对动态变化和速率加速之间的联系提供改进的理论和分析，这将开辟更有效的酶催化剂开发途径。这样一来，这种范式就发展到了“动态决定功能”的模式。在这一应用中，我们提出了新的结构生物学方法，将提供对生物催化剂的高能结构亚状态的原子水平的洞察，这些高能结构亚状态只被瞬时填充(从毫秒到皮秒)。这一知识将为发展对酶系统中的催化过程的更详细的见解奠定基础，并将形成一个平台，为出现最终将促进酶的改进利用的更严格的理论提供平台。

Enzymes are phenomenal catalysts accelerating reactions by as much as 10^21 compared with the rate of the non-catalyzed reaction. In all living things, these enzymes are specialized protein molecules that catalyze biochemical reactions for carrying out specific biological functions. Over a number of years, chemists and biochemists alike have attempted to harness this catalytic potential of enzyme systems to accelerate reactions that do not normally occur in Nature. This exploitation of enzymes as 'designer' catalysts requires in-depth and quantitative understanding of the physical chemistry of enzyme action. The drive to understand the origin of the power of enzyme catalysis has led to the development of quantitative, physical models for enzyme catalysis - the most recent incorporating quantum phenomena such as 'tunnelling' - to explain rate accelerations by enzyme enzymes. This has been augmented by the elucidation of atomic structures of biological catalysts using structural biology methods such as X-ray crystallography and NMR spectroscopy. This has defined the 'structure determines function' paradigm for enzymes and the notion that biological catalysis can be driven, for example, by complementary interactions between substrate molecules (or high energy states thereof) and the protein. Despite these advances, our understanding of biological catalysis is very incomplete, and we are unable to account for several orders of magnitude of the catalytic power of enzymes using current physical models. A more recent focus has been on the role of protein motions or dynamics in driving biological catalysis. This invokes a flexible enzyme catalyst that, when in complex with a substrate, can explore a myriad of different structural states over a variety of different timescales (sub picosecond to seconds). The catalytic power of enzymes is linked to the dynamical properties of the protein, but structural biology methods provide only 'static' depictions of the catalyst, or at best provide a time averaged ensemble of structures that may, or may not, be important in catalysis. The major challenge to the field and one that will open up more effective exploitation of enzyme catalysts in general, is to provide improved theory and analysis of the link between dynamical change and rate acceleration. The paradigm has thus progressed to one in which 'dynamics determines function'. In this application, we propose novel structural biology approaches that will provide atomic level insight into those high energy structural sub-states of a biological catalyst that are populated only transiently (millisecond through to < picosecond). This knowledge will underpin the development of more detailed insight into catalytic processes in enzyme systems and will form a platform for the emergence of more rigorous theory that will ultimately facilitate the improved exploitation of enzymes.