Five non-allelic genes which encode five types of alcohol dehydrogenase subunits have been identified in humans. An additional gene (ADH6) and cDNA, whose coding sequences were not highly analogous to any of the known alcohol dehydrogenase subunits, were recently cloned (Yasunami et al., Proc. Natl. Acad. Sci. USA 88, 7610-7614, 1991). The full-length ADH6 cDNA was expressed in the E.coli expression system and in the in vitro translation system of rabbit reticulocytes. The protein produced had its isoelectric point at pH 8.6, optimum pH at pH 10, and a lower Km for benzylalcohol than for ethanol and propanol. These characteristics are compatible to the properties of mu- or sigma-alcohol dehydrogenase isozyme existing in human stomach, indicating that ADH6 gene encodes the mu- or sigma-alcohol dehydrogenase subunit.