There are 3 isoforms of ADH1B that are relatively common in at least some populations. The ADH1B enzyme with arginine at both positions 48 and 3702 is commonly known as ADH1B*1 (in earlier literature it is called β1-ADH or ADHB*1; Table 1). ADH1B*1 metabolizes ethanol at the slowest rate among the 3 isoforms. It is the most common isoform globally except in much of East Asia, and is the form to which others are compared. The isoform with histidine at position 48 is called ADH1B*2 (β2-ADH or ADHB*2), and differs only due to rs1229984. In vitro, ADH1B*2 oxidizes ethanol much faster than ADH1B*1 (Table 1). Computer modeling suggests that at 17 mM ethanol, ADH1B*2 homodimers could oxidize ethanol at about 11 times the rate of ADH1B*1 homodimers (interpolated from (Chi et al., 2018)); heterodimers behave as equal mixtures of the homodimers (Edenberg and Bosron, 2018). The difference in metabolic rate is much smaller in vivo, due to contributions of the other ADH enzymes and limitations by cofactor levels. Neumark et al. (Neumark et al., 2004) found a small (~14%) but
