title: Novel nicotine oxidoreductase-encoding gene involved in nicotine degradation by Pseudomonas putida strain S16.
abstract: There are quite a few ongoing biochemical investigations of nicotine degradation in different organisms. In this work, we identified and sequenced a gene (designated nicA) involved in nicotine degradation by Pseudomonas putida strain S16. The gene product, NicA, was heterologously expressed and characterized as a nicotine oxidoreductase catalyzing the initial steps of nicotine metabolism. Biochemical analyses using resting cells and the purified enzyme suggested that nicA encodes an oxidoreductase, which converts nicotine to 3-succinoylpyridine through pseudooxynicotine. Based on enzymatic reactions and direct evidence obtained using H(2)(18)O labeling, the process may consist of enzyme-catalyzed dehydrogenation, followed by spontaneous hydrolysis and then repetition of the dehydrogenation and hydrolysis steps. Sequence comparisons revealed that the gene showed 40% similarity to genes encoding NADH dehydrogenase subunit I and cytochrome c oxidase subunit I in eukaryotes. Our findings demonstrate that the molecular mechanism for nicotine degradation in strain S16 involves the pyrrolidine pathway and is similar to the mechanism in mammals, in which pseudooxynicotine, the direct precursor of a potent tobacco-specific lung carcinogen, is produced.
authors.affiliation: Key Laboratory of Microbial Metabolism, Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, People's Republic of China.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Tang
authors.forename: Lijuan
authors.initials: L
authors.lastname: Wang
authors.forename: Xiangzhou
authors.initials: X
authors.lastname: Meng
authors.forename: Lanying
authors.initials: L
authors.lastname: Ma
authors.forename: Shuning
authors.initials: S
authors.lastname: Wang
authors.forename: Xiaofei
authors.initials: X
authors.lastname: He
authors.forename: Geng
authors.initials: G
authors.lastname: Wu
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D002074:Butanones / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D009245:NADH Dehydrogenase / Q000235:genetics; D009538:Nicotine / Q000031:analogs & derivatives / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D016958:Pseudomonas putida / Q000201:enzymology* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D002074:Butanones; D004269:DNA, Bacterial; C081694:pseudooxynicotine; D009538:Nicotine; D010088:Oxidoreductases; C034523:nicotine oxidase; D009245:NADH Dehydrogenase; D003576:Electron Transport Complex IV