The overexpression systems of Cytophag a alcohol dehydrogenase and aldehyde dehydrogenase in Escherichia coli were constructed, and both enzymes were purified to homogeneity. The alcohol dehydrogenase contained 2 g-atoms of zinc per subunit, but the aldehyde dehydrogenase was independent of any metals. Both enzymes showed low substrate specificities. They showed thermostability, although were produced by a psychrophilic bacterium: the half-life times of Cytophag a alcohol dehydrogenase and aldehyde dehydrogenase were over 200 and 65 min at 50°C, respectively. The Km value of Cytophag a alcohol dehydrogenase is 40-50 times lower than that of the Saccharomyces enzyme, and the kcat/Km value of the Cytophag a enzyme is much higher than that of the Saccharomyces enzyme. Ethanol was determined with about 175 times less Cytophag a alcohol dehydrogenase than the Saccharomyces enzyme. The addition of Cytophag a aldehyde dehydrogenase led to an increase in sensibility.
