 Most Caucasians have two major isozymes, while approximately 50% of East Asians have one normal copy of the ALDH2 gene and one variant copy (ALDH2*2, rs671) that encodes an inactive mitochondrial isoenzyme.In native Japanese, this variant ALDH2 gene encodes lysine instead of glutamic acid at amino acid 487 and therefore encodes a product protein that is completely inactive in metabolizing acetaldehyde to acetic acid.In the overall Japanese population, about 57% of individuals are homozygous for the normal gene, 40% are heterozygous for the variant gene, and 3% are homozygous for the variant gene.