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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Dissipation and maintenance of stable states in an enzymatic system: analysis and simulation.
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Dissipation and maintenance of stable states in an enzymatic system: analysis and simulation.

机译：酶系统中稳态的耗散和维持：分析和模拟。

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摘要

The constraint-based analysis has emerged as a useful tool for analysis of biochemical networks. An essential assumption for constraint-based analysis is the formation of a stable steady state. This work investigates dissipation and maintenance of stable states in a simple reversible enzymatic reaction with substrate inhibition. Under mass-action kinetics, the conditions under which the reaction maintains a stable steady state are analytically derived and numerically confirmed. It is shown that, in order to maintain a steady state in the regulated reaction, maximal enzyme activity must be much higher than input rate. Moreover, it is revealed that requirements for large enzyme activity are due to substrate inhibition. It is suggested that high activities of enzymes may play a vital role in protecting a stable state from its catastrophic collapse, giving an additional explanation to an intriguing problem--why the activities of some enzymes greatly exceed the flux capacity of a pathway. In addition, dissipation of the enzymatic reaction is analysed. It is shown that the collapse of stable states is always associated with a point at which dissipation is the highest. Therefore, in order to maintain a stable state, dissipation of the reaction must be less than a critical value. Moreover, although external forcing may not change net mass flow, it may lead to collapse of stable states. Furthermore, when stable states collapse at a critical forcing amplitude and period, dissipation also reaches a highest value. It is concluded that collapse of stable steady state in the enzyme system with substrate inhibition always corresponds to critical points at which dissipation is highest, regardless if the reaction is forced or not. Therefore, for the substrate inhibited reaction, maintenance of stable states is intrinsically related to level of dissipation.
机译：基于约束的分析已成为分析生化网络的有用工具。基于约束的分析的基本假设是形成稳定的稳态。这项工作研究了具有底物抑制作用的简单可逆酶促反应中稳态的耗散和维持。在质量作用动力学下，通过分析推导并数值确定了反应保持稳定稳态的条件。结果表明，为了在调节的反应中保持稳定状态，最大酶活性必须远高于输入速率。此外，揭示了对大酶活性的需求是由于底物抑制。有人提出，酶的高活性可能在保护稳定状态免受灾难性崩溃的影响中起着至关重要的作用，这进一步解释了一个有趣的问题-为什么某些酶的活性大大超过途径的通量。另外，分析了酶促反应的耗散。结果表明，稳态崩溃总是与最大耗散点相关。因此，为了维持稳定状态，反应的耗散必须小于临界值。而且，尽管外部强迫可能不会改变净质量流量，但可能导致稳态崩溃。此外，当稳定状态在临界强迫幅度和周期崩溃时，耗散也达到最大值。结论是，无论是否强迫反应，具有底物抑制作用的酶系统中稳定稳态的崩溃总是对应于耗散最高的临界点。因此，对于底物抑制的反应，稳定状态的维持本质上与耗散水平有关。

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