多步酶促反应的统计性质
Statistical properties of multistep enzyme-mediated reactions
摘要：
酶介导的反应可以在产生最终产物分子之前通过多个中间构象状态进行，并且人们通常希望从产物产生的观察中鉴定这样的中间结构。在本文中，我们解决这个问题，解决各种酶促反应的化学主方程。我们设计了一个类似于量子力学中使用的微扰理论，使我们能够确定第一（<n>）和第二（方差）累积量的分布所创建的产品分子作为底物浓度和中间过程的动力学速率的函数。平均产物通量V=d<n>/dt（或“剂量-反应”曲线）和Fano因子F=方差f<n>都是实际可测量的量，虽然不同反应类型的平均通量通常相同，但Fano因子可能大不相同。这表明定性和定量的方法来区分不同的反应方案，我们探讨这种可能性的背景下，四个样品的多步酶促反应。我们认为，测量的平均通量和Fano因子不仅可以区分反应类型，但也可以提供一些详细的信息的内部，未观察到的动力学速率，这可以做到不测量单分子的过渡事件。
英文摘要：
Enzyme-mediated reactions may proceed through multiple intermediate conformational states before creating a final product molecule, and one often wishes to identify such intermediate structures from observations of the product creation. In this paper, we address this problem by solving the chemical master equations for various enzymatic reactions. We devise a perturbation theory analogous to that used in quantum mechanics that allows us to determine the first (<n>) and the second (variance) cumulants of the distribution of created product molecules as a function of the substrate concentration and the kinetic rates of the intermediate processes. The mean product flux V=d<n>/dt (or "dose-response" curve) and the Fano factor F=variance/<n> are both realistically measurable quantities, and while the mean flux can often appear the same for different reaction types, the Fano factor can be quite different. This suggests both qualitative and quantitative ways to discriminate between different reaction schemes, and we explore this possibility in the context of four sample multistep enzymatic reactions. We argue that measuring both the mean flux and the Fano factor can not only discriminate between reaction types, but can also provide some detailed information about the internal, unobserved kinetic rates, and this can be done without measuring single-molecule transition events.
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