title: Molecular mechanism of nicotine degradation by a newly isolated strain, Ochrobactrum sp. strain SJY1.
abstract: A newly isolated strain, SJY1, identified as Ochrobactrum sp., utilizes nicotine as a sole source of carbon, nitrogen, and energy. Strain SJY1 could efficiently degrade nicotine via a variant of the pyridine and pyrrolidine pathways (the VPP pathway), which highlights bacterial metabolic diversity in relation to nicotine degradation. A 97-kbp DNA fragment containing six nicotine degradation-related genes was obtained by gap closing from the genome sequence of strain SJY1. Three genes, designated vppB, vppD, and vppE, in the VPP pathway were cloned and heterologously expressed, and the related proteins were characterized. The vppB gene encodes a flavin-containing amine oxidase converting 6-hydroxynicotine to 6-hydroxy-N-methylmyosmine. Although VppB specifically catalyzes the dehydrogenation of 6-hydroxynicotine rather than nicotine, it shares higher amino acid sequence identity with nicotine oxidase (38%) from the pyrrolidine pathway than with its isoenzyme (6-hydroxy-l-nicotine oxidase, 24%) from the pyridine pathway. The vppD gene encodes an NADH-dependent flavin-containing monooxygenase, which catalyzes the hydroxylation of 6-hydroxy-3-succinoylpyridine to 2,5-dihydroxypyridine. VppD shows 62% amino acid sequence identity with the hydroxylase (HspB) from Pseudomonas putida strain S16, whereas the specific activity of VppD is ∼10-fold higher than that of HspB. VppE is responsible for the transformation of 2,5-dihydroxypyridine. Sequence alignment and phylogenetic analysis suggested that the VPP pathway, which evolved independently from nicotinic acid degradation, might have a closer relationship with the pyrrolidine pathway. The proteins and functional pathway identified here provide a sound basis for future studies aimed at a better understanding of molecular principles of nicotine degradation.
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China tanghongzhi@sjtu.edu.cn pingxu@sjtu.edu.cn.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Xiongyu
authors.initials: X
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Yangyang
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China tanghongzhi@sjtu.edu.cn pingxu@sjtu.edu.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
mesh_terms: D001711:Biotransformation; D002244:Carbon / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004734:Energy Metabolism; D019143:Evolution, Molecular; D015870:Gene Expression; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008969:Molecular Sequence Data; D009538:Nicotine / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D042041:Ochrobactrum / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D009538:Nicotine; D002244:Carbon; D009584:Nitrogen