Alcohol dehydrogenases metabolize alcohol to acetaldehyde in the first step of alcohol metabolism. The rate at which ethanol is oxidized influences the concentration of ethanol and acetaldehyde. This is the hypothesized mechanism by which ADH variations affect the risk for alcoholism. There are seven alcohol dehydrogenases in humans: ADH1A, ADH1B, ADH1C, ADH4, ADH5, ADH6, and ADH7 [11]. Class I ADHs (ADH1A, ADH1B and ADH1C) contribute to 70% of ethanol metabolism in the liver [12]. Coding variations in ADH1B have a strong effect on the risk for alcoholism; a single nucleotide polymorphism (SNP) that leads to an arginine to histidine change in the coding sequence (rs1229984; R48H) increases the catalytic rate of the enzyme and was shown to be protective against alcoholism [13–20].
