Relationship of Binding to Catalysis in Unimolecular Reactions

A general treatment does not require that the detailed shape of the free energy surface for interaction of S with E contain a discrete minimum corresponding to a stable E-S complex. The only requirement is that the enzyme must interact with the substrate before it is fully converted to the transition state. It is usually 

Formation of an E-S complex results in the saturation kinetics usually associated with enzymic reactions. At a fixed level of enzyme, the rate initially increases linearly with substrate concentration, but then levels off to approach a limiting maximal rate at saturating substrate level. The maximal rate is given by 

kait describes how rapidly the bound states can produce free product and regenerate free enzyme whereas the ratio describes how well the enzyme 

In the case of Fig. IB the enzyme has equal binding affinity for S, TS, and P as indicated by the equal free energy differences between the bound and free forms of each species. The energy barrier for conversion of S to TS is the same as that for conversion of E-S to E-TS, and equals the rate constant, k , for the nonenzymic process. This situation as well does not produce catalysis since the net rate for conversion of S to P is not increased by addition of E as shown by 

Nonenzymic velocity = nfStoiail Velocity with enzyme = fcnlS] + //kni)lSUEl = [S] + [ES1 = k S] + lESl) 

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