Molecular Pharmacology, Vol 15, 313-321, Copyright © 1979 by the American Society for Pharmacology and Experimental Therapeutics

Drug-Protein Interactions: Evaluation of the Binding of Antipsychotic Drugs to Glutamate Dehydrogenase by Quantitative Affinity Chromatography

¹ Institute of Pharmaceutical Chemistry (Centro di Chimica del Farmaco e dei Prodotti Biologicamente Attivi del CNR), University of Padova
² The Laboratory of Chemical Biology, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014 USA

The interactions of psychoactive drugs with bovine glutamate dehydrogenase were evaluated by quantitative affinity chromatography on Perphemazine-Sepharose. An affinity matrix containing a relatively low density of immobilized ligand was used to achieve competitive elution of zones of the enzyme with buffers containing soluble phenotbiazines and butyrophenones. These competitive elution data indicate that all of the drugs tested bind at the same protein site. The variation of elution volume with soluble drug concentration allowed the calculation of apparent dissociation constants for the binding of these substances. Especially among the phenothiazines, the relative magnitudes of the dissociation constants for the various drugs are similar both to the relative inhibitory effects by these substances on dehydrogenase catalysis and to their relative pharmacological potencies. A close but nondirect interrelationship between drug, NADH, and GTP binding to glutamate dehydrogenase was observed by chromatographic elutions with various combinations of these substances in the eluting buffers.

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ACKNOWLEDGMENTS We wish to thank Drs. Norton Neff (National Institute of Mental Health) and David L. Martin (University of Maryland) for their helpful reviews of this manuscript.