▁ast h ma ▁and ▁card i ov asc ular ▁collapse , ▁an ap hy la xis , ▁and ▁even ▁death ▁may ▁occur . ▁ ▁These ▁re actions ▁appear ▁due ▁to ▁a ▁def ic iency ▁in ▁the ▁met abol ism ▁of ▁the ▁eth an ol ▁in ▁the ▁alco hol ic ▁be verage . ▁ ▁Hum ans ▁met abol ize ▁eth an ol ▁primarily ▁through ▁N AD - dependent ▁alco hol ▁de h ydro gen ase ▁( AD H ) ▁class ▁I ▁en zym es ▁( i . e . ▁AD H 1 A , ▁AD H 1 B , ▁and ▁AD H 1 C ) ▁to ▁ac etal de hy de ▁and ▁then ▁met abol ize ▁ac etal de hy de ▁primarily ▁by ▁N AD - dependent ▁al de hy de ▁de h ydro gen ase ▁ 2 ▁( AL D H 2 ) ▁to ▁ac etic ▁acid . ▁ ▁Eastern ▁A si ans ▁have ▁a ▁def ic iency ▁in ▁ac etal de hy de ▁met abol ism ▁in ▁a ▁surprising ly ▁high ▁percentage ▁( appro aching ▁ 5 0 %) ▁of ▁their ▁populations . ▁ ▁The ▁def ic iency ▁has ▁been ▁most ▁thoroughly ▁investig ated ▁in ▁native ▁Japanese ▁who ▁have ▁a ▁variant ▁A LD H 2 ▁alle le ▁term ed ▁gl u 4 8 7 ly s , ▁A LD H 2 * 2 , ▁or ▁A LD H 2 * 5 0 4 ly s ▁which ▁is ▁a ▁single ▁nucle ot ide ▁polym orphism ▁alle le ▁encoding ▁in ▁its ▁am ino ▁acid