The Relaxation Concept of Enzyme Catalysis

The theories on the conformational changes of the enzyme molecule in the course of a catalyzed reaction and the crucial role of these changes for en- 

The main feature of the Sidorenko-Descherevsky approach was the statement that conformational relaxation of the functioning enzyme molecule can acquire an important role in enzyme activity. Meanwhile, the mechanism of the chemical transformation of the substrate was considered as the conventional one. The conformational changes in the course of enzyme relaxation influence the activity of an enzyme, but do not take an immediate part in performing the elementary chemical act. 

The first notion on the deviation of elementary catalytic acts of enzyme reaction, from that prescribed by classical thermodynamic and kinetic approaches, was, probably, formulated in 1971 [19]. It had been shown that the application of basic postulates of activated state theory to the majority of enzyme processes can lead to physically meaningless values of the activation parameters (energy and entropy of activation). It was emphasized that enzyme functioning is more similar to the work of a mechanical construction than to the catalytic homogeneous chemical reaction. The selfconsistent phenomenological relaxation theory of enzyme catalysis was proposed in 1972 [20, 21]. 

What is the principal idea of the relaxation concept This is not simply a question of the conformational relaxation of the substrate-enzyme complex associated with changing the enzyme catalytic activity. The substrate binding to an enzyme active center initiates the conformational relaxation acting as the driving force that pushes the chemical system substrate molecule attached to the catalytic center) along the reaction coordinate. 

Speaking, for certainty, of the substrate binding as the factor triggering the conformational transition of a system to the new state of equilibrium, we have to remember other factors. As noted in Section 4.1, any local chemical 

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The immediate relation to the relaxation concept of enzyme catalysis [3,4, 20, 21] is the theory of rate processes that has been developed by Fain [35]. In this paper. Fain states that the conventional approach to the kinetics of chemical reactions does not hold true for highly ordered macromolecular structures. The traditional approach to the problem implies that all vibrational modes undergo fast relaxation to thermal equilibrium. In the conventional approach to chemical kinetics, the changes in electronic states and nuclear vibration amplitudes were considered separately. Fain has proposed the self-consistent description of simultaneous changes taking place in the... 

I.5. ATP Synthesis from ADP and Pg as Considered from the Viewpoint of the Relaxation Concept of Enzyme Catalysis... 

The results of experiments on acid-base phosphorylation (the pH jump-induced ATP synthesis) performed by isolated or membrane-bound H ATPases could be interpreted on the basis of the relaxation concept of enzyme catalysis. This concept allows us to suggest a model for ATP synthesis consistent with all the experimental data considered above. It has been proposed, in [182-187, 190, 191], that the fast ionization of certain acid... 

Independently of McClare, similar ideas have been put forward by one of us [1, 2] who elaborated on the concept of molecular machines for enzyme catalysis and energy transduction in chemical and biochemical systems. A central point of this concept was founded on the notion of the crucial role of the conformational relaxation of biopolymers in catalyzing biochemical processes. We will consider the application of this relaxation concept to enzymo-logy and bioenergetics in Chapters 4 and 5. We now focus our attention on the general principles of energy transduction by molecular machines. 

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