Researchers have identified SNPs in the ADH1B and ADH1C genes that result in the production of enzymes with different kinetic properties. These SNPs and their effects have been widely studied in different populations (see other articles in this issue). There are three different ADH1B alleles that alter the amino acid sequence of the encoded β subunit (Table 2). The ADH1B*1 allele encodes the β1 subunit that has argi-nine (Arg) at positions 48 and 370;4 this is the reference allele. ADH1B*2 encodes the β2 subunit that has the amino acid histidine (His) at position 48; this allele is common in Asians. ADH1B*3 encodes the β3 subunit that has cysteine (Cys) at position 370; this allele primarily is found in people of African descent. In both the β2 and β3 subunits, the amino acid substitutions occur at an amino acid that makes contact with the coenzyme nicotinamide adenine dinucleotide (NAD+), which is required for ethanol oxidation (Hurley et al. 2002). In both cases, the substitutions result in enzymes that have a 70- to 80-fold higher turnover rate than the β1 subunit because the coenzyme is released more rapidly at the end of the reaction.
