On the Temperature Dependence of Enzyme-Catalyzed Rates
On the Temperature Dependence of Enzyme-Catalyzed Rates
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DOI：
10.1021/acs.biochem.5b01094
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发表时间：
2016-03-29
期刊：
影响因子：
2.9
通讯作者：
Schipper, Louis A.
中科院分区：
文献类型：
--
作者：
Arcus, Vickery L.;Prentice, Erica J.;Schipper, Louis A.
决定任何反应速度的关键变量之一是温度。例如，对于生物系统，温度的影响与酶催化、蛋白质稳定性和温度依赖调节的无数(往往是相反的)贡献交织在一起。我们创造了“大分子速率理论(MMRT)”来描述与稳定性或调节过程无关的酶催化速率的温度依赖性。MMRT的核心是观察到酶催化的反应发生时，Delta C-p的显著值通常为负值。也就是说，酶-底物复合体的热容(C-p)通常大于酶-过渡态复合体的热容(Cp)。与酶催化的经典描述一致，Delta C-p的负值是酶与底物结合相对较弱而与过渡态结合非常紧密的结果。这种负增量C-p的观察对于酶催化速率的温度依赖性具有重要的意义。在这里，我们将介绍MMRT的基本原理。我们提出了一些直接来自MMRT的假设，包括酶的大小的理论证明和它们的最佳温度的基础。我们对嗜冷酶的行为进行了合理化，并描述了一个限制酶在低温环境中进化的“嗜冷陷阱”。生物学的一个显著特征是由酶催化化学反应，而酶驱动新陈代谢的大部分。因此，我们也期待看到MMRT在细胞、整个生物体甚至生态系统层面的特征。
One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes. Central to MMRT is the observation that enzyme-catalyzed reactions occur with significant values of Delta C-p that are in general negative. That is, the heat capacity (C-p) for the enzyme-substrate complex is generally larger than the Cp for the enzyme-transition state complex. Consistent with a classical description of enzyme catalysis, a negative value for Delta C-p is the result of the enzyme binding relatively weakly to the substrate and very tightly to the transition state. This observation of negative Delta C-p has important implications for the temperature dependence of enzyme-catalyzed rates. Here, we lay out the fundamentals of MMRT. We present a number of hypotheses that arise directly from MMRT including a theoretical justification for the large size of enzymes and the basis for their optimum temperatures. We rationalize the behavior of psychrophilic enzymes and describe a "psychrophilic trap" which places limits on the evolution of enzymes in low temperature environments. One of the defining characteristics of biology is catalysis of chemical reactions by enzymes, and enzymes drive much of metabolism. Therefore, we also expect to see characteristics of MMRT at the level of cells, whole organisms, and even ecosystems.