ADH1C is expressed at modest levels in liver (1/3 that of ADH1B), and to a smaller extent in stomach, with little expression in other tissues (Figure 2). There are two major isoforms of ADH1C, and they differ at 2 sites simultaneously: ADH1C*1 (γ1 ADH, ADH1C[Arg272; Ile350]) and ADH1C*2 (γ2 ADH, ADH1C[Gln272;Val350]). The Arg/Gln at position 272 is encoded by rs1693482 and the Ile/Val at 350 by rs698. In vitro kinetic assays show ADH1C*1 is about 1.5 to 2-fold more active than ADH1C*2 (Hurley et al., 2002, Chi et al., 2018) (Table 1). These kinetic differences are almost certainly due to the difference at amino acid 272 (Arg/Gln; rs1693482). Most genetic literature focuses on the other SNP, rs698, for historic and technical reasons (Xu et al., 1988). This does not affect conclusions, because Arg272 is virtually always found together with Ile350, and Gln272 with Val350: the correlation between these SNPs is complete (r2 = 1.0) in 24 of the 26 populations in the 1000 genomes database, and nearly so in the other 2 (r2 = 0.97 in ITU, 0.93 in YRI).
