In the course of phylogenetic evolution, the substrate specificity of alcohol dehydrogenase, the enzyme which detoxicates ethyl alcohol, has apparently broadened. Thus, while the enzyme from yeast oxidizes ethyl alcohol and only a few other alcohols,1 the enzyme of the horse liver is capable of oxidizing a range of other alcohols.1,2 The human enzyme has an even wider range,3 since contrary to the horse enzyme it oxidizes both ethyl alcohol and ethylene glycol. While chemically ethylene glycol is very similar to ethyl alcohol, both these compounds are toxic to man. Detailed studies of the enzymatic oxidation of ethylene glycol demonstrate that ethyl alcohol, the natural substrate, is a potent competitive inhibitor of the oxidation of ethylene glycol.3 Hence, low concentrations of ethyl alcohol prevent the oxidation of large concentrations of ethylene glycol.
These biochemical features of the catalytic behavior of human-liver alcohol dehydrogenase have served as