Novel Nicotine Oxidoreductase-Encoding Gene Involved in Nicotine Degradation by Pseudomonas putida Strain S16
Novel Nicotine Oxidoreductase-Encoding Gene Involved in Nicotine Degradation by Pseudomonas putida Strain S16
复制标题
新型尼古丁氧化还原酶编码基因参与恶臭假单胞菌菌株 S16 降解尼古丁
DOI：
10.1128/aem.02300-08
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发表时间：
2009-02-01
影响因子：
4.4
通讯作者：
Xu, Ping
中科院分区：
文献类型：
--
作者：
Tang, Hongzhi;Wang, Lijuan;Xu, Ping
有相当多的正在进行的关于尼古丁在不同生物体中降解的生化研究。在这项工作中，我们对恶臭假单胞菌S16菌株的尼古丁降解相关基因(命名为nica)进行了鉴定和测序。基因产物NICA被异源表达，并被鉴定为尼古丁氧化还原酶，催化尼古丁代谢的初始步骤。利用静息细胞和纯化的酶进行的生化分析表明，NICA编码一个氧化还原酶，该酶通过伪氧烟碱将尼古丁转化为3-琥珀酰基吡啶。根据酶促反应和H-2O-18标记获得的直接证据，该过程可能包括酶催化脱氢，然后自发水解，然后重复脱氢和水解步骤。序列比较表明，该基因与真核生物中编码NADH脱氢酶亚基I和细胞色素C氧化酶亚基I的基因有40%的相似性。我们的发现表明，S16菌株尼古丁降解的分子机制涉及吡咯烷途径，与哺乳动物的机制相似，在该机制中产生了一种有效的烟草特异性肺癌致癌物的直接前体伪氧烟碱。
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 O-18 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.