Question

Provide a detailed rationale for the observation that an enzyme that stabilizes its Michaelis (ES) complex as much as its transition state does not catalyze a reaction. Include appropriate reaction coordinate diagrams to support your answer.

Answer 1

Enzymes catalyzes a reaction by lowering the activation energy.

In a Michaelis equation when there is formation of ES complex, it should be less stable so that it can easily covert into product and enzyme. During the transition state when ES get prepare to form product, enzyme-induce changes in electron distribution in the substrate and changes its conformational state. These transition states are surrounded by lower energy complexes so that it accelerate the rate of product formation.

Catalysis require relaxation of the transition state energ as early as possible to allow the dissociation products .IN order to catalyse a reaction, it is very important that Michaelis complex should be diffusional having rate of constant approximately10⁹ M⁻¹sec⁻¹. Higher the diffusional event constant, higher will be the rate of relaxation of tansition state and subsequently the formation of product rate.Vice-versa happened when Michaelis complex becomes stabilizes as much as transition state. So when ES complex gets stabilised in the reaction, in the same manner as transition state, there would be no conformaational change and the reaction will set an equilibrium state between ES complex and the reactants that will halt the reaction at this stage and hence no catalysis will take place and product will not form.

This diagram depicts the relation of transition state and ES complex and their significance/effect in prduct formation