Hydrogen bonding in enzymatic catalysis: analysis of energetic contributions.

Enzymes can provide catalysis by increasing the strengthening of hydrogen bonds to groups undergoing charge rearrangement in the course of reaction relative to the strengthening of the hydrogen bonds in the corresponding solution reactions. This can be accomplished by using hydrogen bond donors and acceptors that are stronger than water and by lowering the effective dielectric relative to that in aqueous solution. We suggest that these electrostatic effects are of general significance in enzymatic catalysis. The effective dielectric is lowered by the overall "rigidity" of the folded enzyme, which facilitates the formation of active site interactions, and by the fixation of active site functional groups within the enzyme x substrate complex. This underscores the fundamental interconnection of catalytic mechanisms in enzymatic catalysis.