An Iron-Dependent Alcohol Dehydrogenase Is Involved in Ethanol Metabolism of Aromatoleum aromaticum

The NAD+-dependent alcohol dehydrogenase AdhB from Aromatoleum aromaticum EbN1 belongs to family III of Fe-dependent alcohol dehydrogenases. It was recombinantly produced in Escherichia coli and biochemically characterized, showing activity only with ethanol or n-propanol. The enzyme contained substoichiometric amounts of Fe, Zn and Ni and a yet unidentified nucleotide-like cofactor, as indicated by mass spectrometric data. As suggested by its narrow substrate spectrum and complementation of a related species to growth on ethanol, the most probable physiological function of AdhB is the oxidation of short aliphatic alcohols such as ethanol or n-propanol. AdhB was also tested for its biotechnological applicability as auxiliary enzyme for the conversion of acetate to ethanol in coupled enzyme assays with the tungsten enzyme aldehyde oxidoreductase.