The second step in the metabolism of ethanol, the oxidation of acetaldehyde to acetate, is important for eliminating the potentially toxic acetaldehyde (Zakhari, 2006). Unlike the oxidation of ethanol to acetaldehyde, this step is essentially irreversible (Hurley et al., 2002). There are 19 human aldehyde dehydrogenases, but three closely related ones (68% amino acid sequence identity) are most relevant to the metabolism of acetaldehyde: ALDH1A1, ALDH1B1 and ALDH2 (Jackson et al., 2011, Vasiliou et al., 2004). All three act as homotetramers, and have broad substrate specificities.
