title: Conversion of nornicotine to 6-hydroxy-nornicotine and 6-hydroxy-myosmine by Shinella sp. strain HZN7.
abstract: Nornicotine is a natural alkaloid produced by plants in the genus Nicotiana and is structurally related to nicotine. Importantly, nornicotine is the direct precursor of tobacco-specific nitrosamine N'-nitrosonornicotine, which is a highly potent human carcinogen. Microbial detoxification and degradation of nicotine have been well characterized; however, until now, there has been no information on the molecular mechanism of nornicotine degradation. In this study, we demonstrate the transformation of nornicotine by the nicotine-degrading strain Shinella sp. HZN7. Three transformation products were identified as 6-hydroxy-nornicotine, 6-hydroxy-myosmine, and 6-hydroxy-pseudooxy-nornicotine by UV spectroscopy, high-resolution mass spectrometry, nuclear magnetic resonance, and Fourier transform-infrared spectroscopy analyses. The two-component nicotine dehydrogenase genes nctA1 and nctA2 were cloned, and their product, NctA, was confirmed to be responsible for the conversion of nornicotine into 6-hydroxy-nornicotine as well as nicotine into 6-hydroxy-nicotine. The 6-hydroxy-nicotine oxidase, NctB, catalyzed the oxidation of 6-hydroxy-nornicotine to 6-hydroxy-myosmine, and it spontaneously hydrolyzed into 6-hydroxy-pseudooxy-nornicotine. However, 6-hydroxy-pseudooxy-nornicotine could not be further degraded by strain HZN7. This study demonstrated that nornicotine is partially transformed by strain HZN7 via nicotine degradation pathway.
authors: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Jiguo
authors: J
authors: Qiu
authors: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Na
authors: N
authors: Li
authors: College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.
authors: Zhenmei
authors: Z
authors: Lu
authors: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Youjian
authors: Y
authors: Yang
authors: College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
authors: Yun
authors: Y
authors: Ma
authors: College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
authors: Lili
authors: L
authors: Niu
authors: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China. hejian@njau.edu.cn.
authors: Jian
authors: J
authors: He
authors: College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
authors: Weiping
authors: W
authors: Liu
mesh_terms: D000470:Alkaloids / Q000378:metabolism*; D001711:Biotransformation; D003001:Cloning, Molecular; D007306:Insecticides / Q000378:metabolism*; D009538:Nicotine / Q000031:analogs & derivatives* / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics / Q000378:metabolism; D012230:Rhizobiaceae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013057:Spectrum Analysis
chemical_list: D000470:Alkaloids; D007306:Insecticides; D009538:Nicotine; C005311:nornicotine; C002398:myosmine; D000587:Oxidoreductases Acting on CH-NH Group Donors; C066274:nicotine dehydrogenase
keywords: 6-Hydroxy-myosmine; 6-Hydroxy-nicotine oxidase; 6-Hydroxy-nornicotine; 6-Hydroxy-pseudooxy-nornicotine; Nicotine dehydrogenase; Nornicotine; Shinella sp. HZN7