The best-known ALDH genetic polymorphism is in ALDH2, with the variant form, ALDH2*2 (rs671) encoding for a low activity isoform that has a 100-fold higher Km for acetaldehyde, resulting in a nearly inactive enzyme under physiological conditions after drinking (113). This very prominent variant allele has been seen in about half of the East Asian populations studied (including the Han Chinese, Taiwanese, and Japanese) but has not been observed in populations of Caucasian ancestry (120, 172, 173).
