Ngo L G, Roussel M R
Department of Chemistry, University of Lethbridge, Alberta, Canada.
Eur J Biochem. 1997 Apr 1;245(1):182-90. doi: 10.1111/j.1432-1033.1997.00182.x.
It has been noted that single-enzyme systems can undergo strongly damped transient oscillations. In this paper, we present a nonlinear dynamics analysis of oscillations in undriven chemical systems. This analysis allows us to classify transient oscillations into two groups. In the first group, oscillations arise from rapid oscillatory relaxation to a slower transient relaxation mode. These oscillations are always strongly damped. In the second group, it is the slowest relaxation mode which is implicated in the oscillations so these can be very lightly damped. This second class of oscillations has not previously been studied in enzymology. We show that a remarkably simple single-enzyme system, namely competitive inhibition with substrate flow, generates transient oscillations which belong to the second class. In an attempt to design an experimentally realizable version of this model, we then discovered a system which is capable of sustained oscillations. In this experimentally realizable model, two substrates compete to bind to a macromolecule. The flow of one substrate is controlled by a simple feedback device. Sustained oscillations are observed over a very wide range of parameters. In both models, oscillations are favored by a wide disparity in rates of binding and dissociation of the two substrates to the macromolecule.
人们已经注意到，单酶系统可能会经历强烈阻尼的瞬态振荡。在本文中，我们对无驱动化学系统中的振荡进行了非线性动力学分析。这种分析使我们能够将瞬态振荡分为两组。在第一组中，振荡源于快速振荡弛豫到较慢的瞬态弛豫模式。这些振荡总是强烈阻尼的。在第二组中，振荡涉及最慢的弛豫模式，因此这些振荡可以是非常轻微阻尼的。第二类振荡以前在酶学中尚未被研究过。我们表明，一个非常简单的单酶系统，即具有底物流动的竞争性抑制，会产生属于第二类的瞬态振荡。为了设计这个模型的一个实验可实现版本，我们随后发现了一个能够持续振荡的系统。在这个实验可实现的模型中，两种底物竞争与一种大分子结合。一种底物的流动由一个简单的反馈装置控制。在非常广泛的参数范围内都观察到了持续振荡。在这两个模型中，两种底物与大分子结合和解离速率的巨大差异有利于振荡的发生。
