Facilitated Proton Transfer in Enzyme Catalysis

Abstract

The article proposes that facilitated proton transfer along rigidly and accurately held H bonds in the enzyme-substrate complexes may play a crucial role in enzyme catalysis. In other words, enzymes catalyze not only by lowering the free energy of the transition state (or states), as assumed in all previous theories, but also by enabling the system to reach the transition-state (or states) faster through facilitated proton transfer along strategically fixed H bonds. The available evidence concerning carbonic anhydrase, a-chymotrypsin, trypsin, thiol-subtilisin, RNase, and alcohol dehydrogenases seems to support the proposed mechanism, although decisive information is still wanting. If the present interpretation proves to be correct, it will provide a new dimension for understanding the efficiency and specificity of enzyme action and even more appreciation of the advantage of using proteins to make enzymes.