Characterization of Pseudooxynicotine Amine Oxidase of Pseudomonas putida S16 that Is Crucial for Nicotine Degradation

Pseudooxynicotine amine oxidase (Pnao) is essential to the pyrrolidine pathway of nicotine degradation of Pseudomonas putida strain S16, which is significant for the detoxification of nicotine, through removing the CH(3)NH(2) group. However, little is known about biochemical mechanism of this enzyme. Here, we characterized its properties and biochemical mechanism. Isotope labeling experiments provided direct evidence that the newly introduced oxygen atom in 3-succinoylsemialdehyde-pyridine is derived from H(2)O, but not from O(2). Pnao was very stable at temperatures below 50 °C; below this temperature, the enzyme activity increased as temperature rose. Site-directed mutagenesis studies showed that residue 180 is important for its thermal stability. In addition, tungstate may enhance the enzyme activity, which has rarely been reported before. Our findings make a further understanding of the crucial Pnao in nicotine degradation.