Molecular Pharmacology, Vol 9, 191-198, Copyright © 1973 by the American Society for Pharmacology and Experimental Therapeutics

The Inhibition of Alcohol and Aldehyde Dehydrogenases by Propranolol

¹ Laboratory of Chemical Neurobiology, Department of Psychiatry, McGill University, Montreal 112, Quebec, Canada

Propranolol inhibits horse liver alcohol dehydrogenase (EC 1.1.1.1), yeast alcohol dehydrogenase (EC 1.1.1.1), and pig brain aldehyde dehydrogenase (EC 1.2.1.3). In each case the inhibition is reversible. The form of the inhibitions is consistent with the formation of an enzyme-propranolol complex which in some cases may bind the coenzyme. Various kinetic constants for the inhibitions have been calculated; K_i values lie between 100 and 360 µM for these enzymes. Propranolol increases the dissociation constants of both 5'-AMP and phenanthroline from their complexes with liver alcohol dehydrogenase, but ternary complexes of enzyme with propranolol and 5'-AMP or phenanthroline are formed. Propranolol in concentrations up to 1 mM inhibits neither rat liver lactate dehydrogenase (EC 1.1.1.27) nor malate dehydrogenase (EC 1.1.1.37) from rat liver or from pig heart. Pronethalol inhibits liver alcohol dehydrogenase with a K_{i slope} value of 84 µM. From these enzymatic results propranolol has the potential of slowing ethanol oxidation, and since aldehyde dehydrogenase is involved in the catabolism of the biogenic amines, propranolol may modify the metabolism of the deaminated biogenic amines.