The three most studied alleles of ADH1B usually are referred to as ADH1B*1 (the reference allele, which encodes the β2 form of the enzyme and carries the amino acid arginine [Arg] at positions 48 and 370 in the amino acid chain), ADH1B*2 (encoding β2 and carrying histidine [His] at position 48: ADH1B-His48Arg370; rs1229984), and ADH1B*3 (encoding β3 and carrying cysteine [Cys] at position 370: ADH1B-Arg48Cys370; rs2066702). The encoded enzyme variants differ significantly in the ethanol concentrations they require for maximal function and in how fast they metabolize the ethanol (i.e., in their kinetic properties), with both ADH1B*2 and ADH1B*3 encoding enzymes with faster turnover (i.e., higher Vmax) than the reference allele (see table 1). One study of Japanese alcoholics who checked into a hospital 1 day after heavy drinking showed that those who carried two copies of (i.e., were homozygous for) the ADH1B*1 allele still had significant blood ethanol concentrations (BECs), whereas those who carried at least one ADH1B*2 allele had very low BECs, consistent with a more rapid ethanol metabolism by ADH1B*2 (Yokoyama et al. 2007). The current model
