There are 2 main isoforms of the ALDH2 enzyme. The one common in most of the world, ALDH2*1, has glutamate at amino acid 487 of the mature protein (504 of the precursor). A variant, ALDH2*2, has a lysine there instead, encoded by rs671. Allele frequencies for ALDH2*2 are highest in Han Chinese and Japanese, with lower frequencies elsewhere in Asia; it is rarely found outside Asia (Table 2). Even a single ALDH2*2 subunit renders the tetrameric enzyme nearly inactive under physiological conditions (Crabb et al., 1989, Zhou and Weiner, 2000, Hurley et al., 2002) and it is also more rapidly degraded (Xiao et al., 1996).
