Characterization of rat testicular alcohol dehydrogenase.

A protein from rat testes that catalyzes the oxidation of ethanol in the presence of NAD+, but not NADP+, has been characterized enzymatically and compared to that of hepatic alcohol dehydrogenase obtained from the same animals. The testicular enzyme, like the hepatic enzyme, has a Km value for ethanol in the 0.5-1.0-mM range and can utilize other alcohols such as n-propanol, n-butanol, and isobutanol, although the Km values for these other alcohols are considerably lower (0.03-0.08 mM) that that for ethanol. The testicular enzyme is more heat-labile than is the hepatic enzyme. Finally, the testicular enzyme catalyzes the oxidation of retinol and its retinol dehydrogenase activity is inhibited by ethanol.