DHDH encodes an enzyme that belongs to the family of dihydrodiol dehydrogenases, which exist in multiple forms in mammalian tissues and are involved in the metabolism of xenobiotics and sugars. These enzymes catalyze the NADP1-linked oxidation of transdihydrodiols of aromatic hydrocarbons to corresponding catechols. This enzyme is a dimeric dihydrodiol dehydrogenase, and it differs from monomeric dihydrodiol dehydrogenases in its high substrate specificity for trans-dihydrodiols of aromatic hydrocarbons in the oxidative direction.