[ADH isoenzymes]

ADH isoenzymes are grouped in three distinctive "classes" based on their enzymatic characteristics. Until recently, five kinds of subunit (alpha, beta, gamma, pi and chi) governed by five nonallelic genes, ADH 1, ADH 2, ADH 3, ADH 4 and ADH 5, respectively, have been identified. However, additional forms have been reported. Thus, a mammalian gastric enzyme has been isolated and proven to be a new alcohol dehydrogenase class (class IV). Furthermore, the human protein encoded ADH 6 has been reported. In this review, I shall present the current knowledge concerning the expression and the catalytic properties of ADH isoenzymes, and the possible relationships of polymorphism of ADH isoenzymes to individual differences in alcohol-oxidizing capacity and to liability to alcohol abuse.