Optimum motion principle

THE PRINCIPLE OF OPTIMUM MOTION IN ELEMENTARY ACTS OF CHEMICAL AND ENZYMATIC PROSESSES. 

Principle of optimum motion and mechanisms of enzymes reactions... 

Each stage of the catalytic process should obey the principle of optimum motion (Sections 2. and 2.9). Eventually, constrained pretransition-state complex that activates cleavage or formation of chemical bonds, have to be formed. The realization of this last requirement is the most challenging and difficult problem of the mimicking enzymes processes. 

Likhtenshtein, G.I. (1977a) On the principle of optimum motion in elementary acts of chemical and biological processes, I. Estimation of the synchronization factor for model processes. Kinetika I Kataliz (Kinetics and Catalysis), 28 878-882. 

Enzyme catalysts typically have low activation energies. The synchronized action of multi-atom displacements to optimize the interaction energy with the pretransition-state complex imphes a decrease in the entropic state of the complex. This has been analyzed by Liktensteinl l, who formulated the principle of optimum motion , in contrast to the principle of minimum motion . 

When a reactant molecule adsorbs on a particular site, entropy is lost compared with the reactant state in solvent or gas phase. This was described earlier in the chapter on zeolites. Within the rigid lock and key model, this entropy loss would be maximum, thus reducing the free energy gained upon adsorption. This is an additional reason why an optimum fit between reactant and enzyme cavity is not preferred. When the fit between the reactant and the cavity is not optimum, the reactant will maintain some mobility in the adsorbed state, hence the entropy loss is less. The basic mechanistic principles for enzyme catalysis discussed so far include the induced fit of the enzyme cavity as a response to substrate shape and size, pretransition-state stabilization of activated molecules and the principle of optimum motion. A reaction that proceeds through intermediates via transient covalent bonds is preferred. 

The principle of optimum motion in elementary acts of chemical and enzymatic processes... 

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