Isomerization of Transitory Complexes and Stable Enzyme Forms

7 ISOMERIZATION OF TRANSITORY COMPLEXES AND STABLE ENZYME FORMS 

Isomerization of a transitory complex in any mechanism does not affect the form of the rate equation, but if a stable enzyme form isomerizes, additional terms occur in the denominator. 

The following reaction shows an isomerization of transitory EA and EQ complexes in the Ordered Bi Bi mechanism. 

The isomerization of a transitory conplex does not affect the algebraic form of the velocity equation in the absence or in the presence of products, but the composition of some kinetic constants are changed by introducing the rate constants for isomerization k and jtff in the forward dii on and and k in the reverse direction. The isomerization of transitory complexes is very common in many enzyme reactions, particularly among pyridine-dependent dehydrogenases. 

Although isomerization of transitory forms does not alter the algebraic form of the rate equation, the existence of isomerization of non-central transitory complexes can often be inferred from kinetic data alone, or from comparison of kinetic data with the equilibrium constant (Chapter 10). 

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