Retinol and alcohol dehydrogenases in retina and liver

Isozymes of alcohol dehydrogenase (alcohol: NAD⁺ oxidoreductase, EC 1.1.1.1) and retinol (vitamin A₁) dehydrogenase (retinol: NAD⁺ oxidoreductase) were studied in retina and liver extracts of rat by starch-gel electrophoresis. The retina demonstrated two zones of retinol dehydrogenase activity and a separate zone of alcohol dehydrogenase activity. The liver had single zones each of retinol and alcohol dehydrogenase activity, neither of which coincided with the three zones from the retina. It is concluded on the basis of the electrophoretic findings supplemented with inhibition, heat inactivation, and pH studies that these five zones represent five different enzymes, and that vitamin A is oxidized in the retina and the liver by specific and distinct enzymes. Liver-type alcohol dehydrogenase is absent from the eyes and eye-type is absent from the liver.