The heat released during catalytic turnover enhances the diffusion of an enzyme

摘要

酶通过降低化学转化反应的活化能来催化这些反应。人们传统上假设，一次催化事件(一次rn"周转"事件)中所释放的热量不会以任何方式对酶产生扰动。在这篇论文中，作者利用rn"单分子荧光关联光谱"显示，对于催化具有大反应焓值的化学反应的酶(如过氧化氢酶或碱性磷酸酶)来说，催化过程中在蛋白活性点上所释放出的热量会瞬时转移蛋白的质量中心，实质上相当于产生一个推动酶前进的反冲效应。这项研究可帮助解释最近获得的以下发现：酶的扩散性在催化过程中会以依赖于基质的方式提高。%Recent studies have shown that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis. Although this observation has been reported and characterized for several different systems, the precise origin of this phenomenon is unknown. Calorimetric methods are often used to determine enthalpies from enzyme-catalysed reactions and can therefore provide important insight into their reaction mechanisms. The ensemble averages involved in traditional bulk calorimetry cannot probe the transient effects that the energy exchanged in a reaction may have on the catalyst. Here we obtain single-molecule fluorescence correlation spectroscopy data and analyse them within the framework of a stochastic theory to demonstrate a mechanistic link between the enhanced diffusion of a single enzyme molecule and the heat released in the reaction. We propose that the heat released during catalysis generates an asymmetric pressure wave that results in a differential stress at the protein-solvent interface that transiently displaces the centre-of-mass of the enzyme (chemoacoustic effect). This novel perspective on how enzymes respond to the energy released during catalysis suggests a possible effect of the heat of reaction on the structural integrity and internal degrees of freedom of the enzyme.