Models for Enzymatic Activity

In 1948, Pauling proposed a model for understanding enzyme activity. Pauling stated 

I think that enzymes are molecules that are complementary in stmcture to the activated complexes of the reactions they catalyze. The attraction of the enzyme molecule for the activated complex would thus lead to a decrease in its energy and hence to a decrease in the energy of activation of the reaction, and an increase in the rate of the reaction. 

Computational Organic Chemistry, Second Edition. Steven M. Bachrach 2014 John Wiley Sons, Inc. Published 2014 by John Wiley Sons, Inc. 

This argument goes by the name transition state stabilization and remains the dominant model in the enzymatic community today Amyes and Richard recently reviewed a selection of enzymes whose behaviors are well understood within this Pauling paradigm. 

This latter quantity is the difference in free energy between the MC and the TS. For all enzymes, AG j is less than AG j, oftentimes very much so. 

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