Stereochemistry and the Mechanism of Enzymatic Reactions

The isolation and purification of an enzyme makes it possible to consider the reaction which it catalyzes from the standpoint of organic chemistry, i.e. as a reaction between organic molecules in which the catalyst happens to be a protein. Such a consideration allows the tools of physical organic chemistry to be applied to the the study of the enzyme mechanism, and, since a number of enzymes have been purified, to obtain correlations of what might otherwise appear to be unrelated processes. One of the particularly powerful tools used in the elucidation of chemical mechanisms is stereochemistry, and it would be expected that similar conditions might lead to a clarification of enzymatic mechanisms and enzyme-substrate intermediates. In this article, the effect of enzymatic reactions on the configuration of the asymmetric carbon atoms involved in the reaction has been examined and the observed changes described by mechanisms which are compatible with both the chemical and biochemical evidence.