Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Langmuir. 2021 Oct 26;37(42):12263-12270. doi: 10.1021/acs.langmuir.1c01360. Epub 2021 Oct 14.
Enzyme-based systems have been shown to undergo chemotactic motion in response to their substrate gradient. This phenomenon has been exploited to direct the motion of enzymes and enzyme-attached particles to specific locations in space. Here, we propose a new kinetic model to analyze the directional movement of an ensemble of protein molecules in response to a gradient of the ligand. We also formulate a separate model to probe the motion of enzyme molecules in response to a gradient of the substrate under catalytic conditions. The only input for the new enzymatic model is the Michaelis-Menten constant which is the relevant measurable constant for enzymatic reactions. We show how our model differs from previously proposed models in a significant manner. For both binding and catalytic reactions, a net movement up the ligand/substrate gradient is predicted when the diffusivity of the ligand/substrate-bound protein is lower than that of the unbound protein (positive chemotaxis). Conversely, movement down the ligand/substrate gradient is expected when the diffusivity of the ligand/substrate-bound protein is higher than that of the unbound protein (negative chemotaxis). However, there is no net movement of protein/enzyme when the diffusivities of the bound and free species are equal. The work underscores the critical importance of measuring the diffusivity of the bound protein and comparing it with that of the free protein.
基于酶的系统已被证明会在其底物梯度的刺激下发生趋化运动。这种现象已被用于引导酶和酶附着颗粒向空间中的特定位置运动。在这里，我们提出了一个新的动力学模型来分析在配体梯度下蛋白质分子的定向运动。我们还制定了一个单独的模型来探测酶分子在催化条件下对底物梯度的运动。新酶模型的唯一输入是米氏常数，这是酶反应的相关可测量常数。我们展示了我们的模型与以前提出的模型有显著的不同。对于结合和催化反应，当配体/底物结合蛋白的扩散系数低于未结合蛋白时（正趋化性），预测会沿着配体/底物梯度向上产生净运动。相反，当配体/底物结合蛋白的扩散系数高于未结合蛋白时（负趋化性），预计会沿着配体/底物梯度向下产生运动。然而，当结合和游离物质的扩散系数相同时，蛋白质/酶没有净运动。这项工作强调了测量结合蛋白的扩散系数并将其与游离蛋白的扩散系数进行比较的重要性。
