Alcohol dehydrogenase, molecular model. Alcohol dehydrogenase (ADH) is an enzyme that facilitates the break-down of alcohols in the body, which could otherwise be toxic. The alcohol is converted to acetaldehyde, an even more toxic molecule, which is then quickly converted into acetate and other molecules that can be utilised by our cells. There are at least nine different forms of ADH that mix and match their subunits in order to create different forms of the enzyme. These mixed dimers are able to target other substances, such as retinol, steroids, and fatty acids.