Monomeric and dimeric quinoprotein alcohol dehydrogenase from alcohol-grown Pseudomonas BB1

Summary: Pseudomonas BB1, grown on alcohols, contained a quinoprotein alcohol dehydrogenase, whose substrate specificity was between those of typical methanol dehydrogenases and ethanol dehydrogenases, and which had a higher turnover number and a different amino acid composition. The enzyme occurred in a dimeric as well as in a monomeric form, and the ratio in which the two forms were found depended on the culture conditions. The mechanism of action and the substrate specificity and affinity of the two forms were identical, while the turnover number of the dimer was twice that of the monomer. This indicates that the catalytic activity of the monomer does not change on dimerization. On inactivating alcohol oxidation of whole cells with cyclopropanol, monomeric and dimeric enzyme became fully inactivated. It is tentatively concluded that both forms participate in alcohol oxidation in vivo.