Pure and Applied Chemistry

Abstract: This paper begins with a brief review of theories and concepts that have influenced today's view of enzyme catalysis: transition-state stabilization, entropy, orbital steering, proximity, and intramolecularity. The discussion then launches into the "spatiotemporal" model of enzyme catalysis in which fast intramolecular and enzymatic rates are ascribed to short distances that are imposed rigidly upon the reacting entities. An equation relating rate and distance is set forth, as are experimental and computational data supporting this relationship. Finally, enzyme systems themselves are analyzed in terms of the distance parameter and the so-called "split-site" model in which ground-state geometries play a crucial role. Among the many surprising conclusions is a transition-state stabilization by noncovalent forces (e.g., hydrogen-bonding) that are positioned far away from the actual transition-state chemistry. The model also confronts and dismisses the claim in classical enzymology that the ubiquitous enzyme-substrate complex is either inconsequential or inhibitory to the overall reaction rate.