SPECIFICITY AND FUNCTION OF ALCOHOL DEHYDROGENASES

University Of Iowa, Iowa City IA

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Abstract

DESCRIPTION: (Adapted from the Investigator's Abstract) The overall objectives of this research are to determine the specificities of alcohol dehydrogenases for substrates and inhibitors, to elucidate the functions of the enzymes in the metabolism of alcohols and carbonyl compounds, and to develop agents to inhibit metabolism of particular substrates that might be involved in alcoholism. Liver alcohol dehydrogenase is a rate-limiting factor in alcohol metabolism, but the tissue distribution and multiplicity of isoenzymes and their broad specificities for substrates suggest that the enzymes oxidize not only ethanol but also a great variety of endogenous substrates. Furthermore, ethanol oxidation may accelerate the reduction of carbonyl compounds by a coupled enzymatic reaction that disturbs metabolism of other substrates. The specificities of the horse E and S, mouse A (1) and C(4), and the human alpha, beta 1, gamma 2, pi and sigma enzymes on various substrates will be defined by steady-state and transient kinetics. The mechanisms of the enzymes and the rate constants for each step will be determined, so that specificity data can be correlated with binding and catalysis. Uncompetitive inhibitors of the enzymes will be developed in order to better define specificity and to prevent metabolism of methanol or ethylene glycol and compounds that might contribute to alcoholism. Three-dimensional structures of selected complexes will be determined by x-ray crystallography in order to confirm and extend models of active site topologies for prediction of specificities. The kinetic parameters determined in vitro will be used to simulate metabolism of alcohols and carbonyl compounds in mice and men, and the rates of the coupled exchange will be simulated in order to assess the capabilities of the enzymes to alter metabolic states in vivo.