The tools of transition state theory provide a powerful analytical framework for interpreting the role of catalysts.

In transition state theory, we view progress along a reaction pathway as following the reaction coordinate where intermediates and stable forms are separated by transition states, energy barriers which must be crossed. The rate of the reaction is determined by the fraction of reagent possessing sufficient energy to achieve the transition state.

The rate of a reaction may be increased by increasing the concentration of reagents present at the rate determining step, increasing the temperature, or lowering the transition state barrier. The last represents the function of a catalyst, to lower the transition state barrier. The activity of protein enzymes is much more coherent if you understand that the enzyme is lowering the energy of the transition state.