Alcohol dehydrogenases from a facultative methylotrophic bacterium

Alcohol-oxidizing enzymes of the facultative methylotroph PAR were investigated after growth of the bacteria on methanol and ethanol. During methanol growth only a phenazine methosulfate-linked alcohol dehydrogenase was detected. This enzyme had broad specificity for primary alcohols and was also capable of oxidation of secondary alcohols. It had a molecular weight of 112,000, was composed of two subunits of equal molecular weight, and showed an absolute requirement for ammonium ion for activation. During ethanol growth this enzyme was absent and was replaced by a typical nicotinamide adenine dinucleotide-linked alcohol dehydrogenase of molecular weight 150,000. The latter enzyme also had broad specificity but could not oxidize methanol. This enzyme was not found during methanol growth. These data show that the organism has two distinctly separate mechanisms for oxidation of alcohols.