ADH4 (π-ADH) has Km for ethanol of 34 mM (Table 1). Its expression is relatively high in liver and extremely low elsewhere. A paradox is that there are over 5500 eQTL for ADH4, but all are in tissues in which expression is extremely low; there are no significant eQTLs affecting the expression of ADH4 in liver. There are few coding variants in ADH4, one of which (Ile309Val, rs1126671) affects the stability of the enzyme and its binding of ethanol (Stromberg et al., 2002); it is relatively common in Europeans (MAF = 0.30) and Africans (MAF=0.14) but rare in East Asians (MAF ~ 0.001).
