Catalyzes the NAD-dependent oxidation of glycerol to dihydroxyacetone (glycerone). Allows microorganisms to utilize glycerol as a source of carbon under anaerobic conditions. Exhibits a rather broad substrate specificity since it can also oxidize 1,2-propanediol and 2,3-butanediol and reduce dihydroxyacetone. Cannot use NADP(+) as an electron acceptor for the oxidation of glycerol. glycerol + NAD(+) = dihydroxyacetone + H(+) + NADH Inhibited by zinc. Polyol metabolism; glycerol fermentation; glycerone phosphate from glycerol (oxidative route): step 1/2. Homohexamer. Belongs to the iron-containing alcohol dehydrogenase family.