It is helpful to emphasize what enzymes can and cannot do.
- Accelerate reactions by factors from 109 to 1020. This capability allows the millions of reactions necessary in your body to proceed on the short time scales that they do.
- Recognize substrates
, the reactants of the chemical reactions enzymes catalyze, sometimes with exquisite sensitivity. Some enzymes are so specific they will not recognize a molecule that differs from its preferred substrate by as little as a single methyl (-CH3) group.
- Alter the thermodynamics of a reaction. Enzymes help reactants and products of a reaction to reach equilibrium much faster than otherwise would happen, but enzymes do not alter their equilibrium concentrations. If more products are added from outside the system, for example, enzymes will accelerate the reverse reaction to the same extent as the forward reaction.
The reason for these capabilities and drawbacks is that enzymes act in the same way as all catalysts, by stabilizing the transition state of a reaction.