The objective of our proposed research is to provide enhanced understanding at the molecular level of the mechanisms of substrate inhibition, and activation by chloride and imidazole, of the liver alcohol dehydrogenase reaction. The EE isoenzyme of horse liver alcohol dehydrogenase will be studied, using fluorescence techniques and rapid reaction kinetics. The mechanisms by which high ethanol concentrations, chloride and imidazole modify the rate constant for NADH dissociation from the enzyme will be sought. The concentration dependence of each effect and rates of the various interactions will be quantitated. We intend to evaluate the roles of ligand-NADH interactions, ligand-protein interactions and protein conformational changes in these phenomena. The results of our studies should elucidate some of the factors affecting the rate of ethanol metabolism.