A HUMAN ALCOHOL-DEHYDROGENASE GENE (ADH6) ENCODING AN ADDITIONAL CLASS OF ISOZYME

The human alcohol dehydrogenase (ADH; alcohol:NAD+ oxidoreductase, EC 1.1.1.1) gene family consists of five known loci (ADH1-ADH5), which have been mapped close together on chromosome 4 (4q21-25). ADH isozymes encoded by these genes are grouped in three distinct classes in terms of their enzymological properties. A moderate structural similarity is observed between the members of different classes. We isolated an additional member of the ADH gene family by means of cross-hybridization with the ADH2 (class I) cDNA probe. cDNA clones corresponding lo this gene were derived from PCR-amplified libraries as well. The coding sequence of a 368-amino-acid-long open reading frame was interrupted by introns into eight exons and spanned approximately 17 kilobases on the genome. The gene contains a glucocorticoid response element at the 5' region. The transcript was detected in the stomach and liver. The deduced amino acid sequence of the open reading frame showed about 60% positional identity with known human ADHs. This extent of homology is comparable to interclass similarity in the human ADH family. Thus, the newly identified gene, which is designated ADH6, governs the synthesis of an enzyme that belongs to another class of ADHs presumably with a distinct physiological role.