Tri- and tetramethylhydroquinone as electron donors for ammonia monooxygenase in whole cells ofNitrosomonas europaea

Ten redox reagents have been tested as electron donors to ammonia monooxygenase in whole cells of Nitrosomonas europaea. Positive results were obtained with tri- and tetramethylhydroquinone. An earlier study showed that phenol was converted into hydroquinone by the monooxygenase. Cells were therefore incubated with trimethylphenol, to see if its hydroxylation to trimethylhydroquinone would lead to a self-sufficient conversion of trimethylphenol into trimethylquinone. No trimethylquinone could be detected. The maximal rates of propene epoxidation obtained with tri-and tetramethylhydroquinone were 1.8 and 4.6 μmol · h−1 · mg protein−1, respectively.