Inhibition Studies on Liver Alcohol Dehydrogenase

Abstract

The rate of reaction of liver alcohol dehydrogenase with iodoacetamide is independent of pH between pH 6–10. Orthophenanthroline, ADP‐ribose and ADP protect the enzyme against alkylation. For iodoacetate, the rate of alkylation decreases with increasing pH over the range 7–9 and reflects the titration of a group with a pK of 7.9. Imidazole enhances the rate of alkylation by both iodoacetamide and iodoacetate and renders the rate of alkylation by iodoacetate pH independent. The interactions of ADP‐ribose and imidazole with the enzyme are shown to be independent of each other. A mechanism is suggested in which the substrate and coenzyme are simultaneously bound to zine. Mechanisms for the activation of both reaction partners are presented.