The ILE349VAL variant has been designated as I350V based on numbering which includes the translation initiation codon (Edenberg, 2007).
Hoog et al. (1986) found 2 amino acid differences between the gamma-1 and gamma-2 alleles: an arg271-to-gln (R271Q; 103730.0001) substitution in exon 6 and an ile349-to-val (rs698) substitution in exon 8 of the ADH1C gene. They determined that the R272Q substitution was responsible for the differences in enzymatic properties, whereas the I350V substitution had no special importance. The location of R272Q appeared important for total charge and catalytic properties, as well as NADH coenzyme interaction.
The gamma-1 allele, now known as ADH1C*1, was originally defined as a gamma subunit that has arg272 and ile350 (Hoog et al., 1986). In almost all cases, these 2 SNPs are in linkage disequilibrium with one another. The gamma-2 allele, now known as ADH1C*2, has gln272 and val350. Homozygosity for the ADH1C*1 allele has a 70% higher turnover rate than homozygosity for ADH1C*2 allele (Edenberg, 2007).
Xu et al. (1988) used the I350V substitution to distinguish ADH1C*1 from ADH1C*2 by means of allele-specific oligonucleotide probes.
Osier et al. (1999) showed that I350V substitution is in linkage disequilibrium with the ADH1B arg48-to-his (R48H; 103720.0001) substitution, and identified the R48H variant as being responsible for differences in ethanol metabolism and alcoholism (103780) among Taiwanese, with the I350V variant showing association only because of linkage disequilibrium.
Chai et al. (2005) examined ADH1B, ADH1C, and ALDH2 polymorphisms in 72 alcoholic and 38 nonalcoholic healthy Korean men; 48 patients had type I alcoholism, and 24 had type II alcoholism. The frequency of ADH1B*1 (103720.0001) and ADH1C*2 alleles was significantly higher in men with type II alcoholism (103780) than in men with type I alcoholism and in healthy men. The frequency of the ALDH2*1 (100650.0001) allele was significantly higher in men with alcohol dependence than in healthy men. Chai et al. (2005) suggested that the genetic characteristics of alcohol metabolism in type I alcoholism fall between nonalcoholism and type II alcoholism.
Among 9,080 Caucasian Danish men and women using the Michigan Alcohol Screening Test, Tolstrup et al. (2008) found that men heterozygous or homozygous for the slower metabolizing ADH1C*2 allele had a 40 to 70% higher risk for heavy or excessive alcohol intake compared to those homozygous for the fast metabolizing ADH1C*1 allele. Similar results were found for women, but effect sizes were smaller and reached significance only for heavy drinking.
