Comparison of the ADH7 gene structure in Caucasian and Japanese subjects

The ADH 7 gene, encoding the sigma-alcohol dehydrogenase isozyme, was cloned from a Caucasian genomic DNA library. Comparison of the nucleotide sequence of its exon 7 with that of an ADH 7 previously cloned from a Japanese subject revealed a substitution of the glycine-287 in the Caucasian sigma isozyme with valine in the Japanese. Since a possible mutation at this site could account for ethnic differences in the gastric activity of this isozyme, the frequency of this change was examined in both races. The exon 7 of the ADH 7 was amplified by PCR from 7 Caucasian and 7 Japanese genomic DNA and applied to restriction fragment length polymorphism analysis, using Ava II to digest the sequence encoding glycine-287 and Mae III to digest that encoding valine-287. Regardless of ethnicity, all PCR amplicons were digested by Ava II and none by Mae III, suggesting that the ethnic difference in the 287 amino acid may represent an uncommon mutation, which does not account for the high frequency of minimal activity of the sigma-alcohol dehydrogenase in the Japanese stomach compared to those of non-Orientals.