Polymorphism of human liver alcohol dehydrogenase: identification of ADH2 2-1 and ADH2 2-2 phenotypes in the Japanese by isoelectric focusing.

Liver homogenate-supernatants from most Japanese exhibit an "atypical" pH optimum for ethanol oxidation at pH 8.8 instead of 10.5, the "typical" pH-activity optimum. It has been proposed that atypical livers contain alcohol dehydrogenase isozymes with beta 2 subunits while typical livers contain isozymes with beta 1 subunits, both produced by the ADH2 gene. Because it is difficult to differentiate the atypical ADH2 2-2 phenotype from the ADH2 2-1 phenotype by starch gel electrophoresis, an agarose isoelectric focusing procedure was developed that clearly separated the atypical Japanese livers into two groups, A1 and A2. The beta beta isozymes in A1 and A2 livers were purified. Type A1 livers contained a single beta beta isozyme with an atypical pH-rate profile; it was designated beta 2 beta 2. Three beta beta isozymes were isolated from A2 livers, two of which corresponded to beta 1 beta 1 and beta 2 beta 2. A third, absent from the typical and the atypical A1 livers, had an intermediate mobility; it was designated beta 2 beta 1. Type A1 livers are, therefore, the homozygous ADH2 2-2 phenotype, and type A2 livers, the heterozygous ADH2 2-1 phenotype. The ADH2 2-2 phenotype was found in 53% of 194 Japanese livers, and the ADH2 2-1 phenotype, in 31%. Accordingly, the frequency of ADH2(2) was 0.68.