title: Novel three-component Rieske non-heme iron oxygenase system catalyzing the N-dealkylation of chloroacetanilide herbicides in sphingomonads DC-6 and DC-2.
abstract: Sphingomonads DC-6 and DC-2 degrade the chloroacetanilide herbicides alachlor, acetochlor, and butachlor via N-dealkylation. In this study, we report a three-component Rieske non-heme iron oxygenase (RHO) system catalyzing the N-dealkylation of these herbicides. The oxygenase component gene cndA is located in a transposable element that is highly conserved in the two strains. CndA shares 24 to 42% amino acid sequence identities with the oxygenase components of some RHOs that catalyze N- or O-demethylation. Two putative [2Fe-2S] ferredoxin genes and one glutathione reductase (GR)-type reductase gene were retrieved from the genome of each strain. These genes were not located in the immediate vicinity of cndA. The four ferredoxins share 64 to 72% amino acid sequence identities to the ferredoxin component of dicamba O-demethylase (DMO), and the two reductases share 62 to 65% amino acid sequence identities to the reductase component of DMO. cndA, the four ferredoxin genes, and the two reductases genes were expressed in Escherichia coli, and the recombinant proteins were purified using Ni-affinity chromatography. The individual components or the components in pairs displayed no activity; the enzyme mixture showed N-dealkylase activities toward alachlor, acetochlor, and butachlor only when CndA-His6 was combined with one of the four ferredoxins and one of the two reductases, suggesting that the enzyme consists of three components, a homo-oligomer oxygenase, a [2Fe-2S] ferredoxin, and a GR-type reductase, and CndA has a low specificity for the electron transport component (ETC). The N-dealkylase utilizes NADH, but not NADPH, as the electron donor.
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Cheng-Hong
authors.initials: CH
authors.lastname: Wang
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Shi-Kai
authors.initials: SK
authors.lastname: Deng
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Ya-Dong
authors.initials: YD
authors.lastname: Wu
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yao
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yan
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China hejian@njau.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: He
authors.affiliation: Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Shun-Peng
authors.initials: SP
authors.lastname: Li
mesh_terms: D000081:Acetamides / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D003640:Dealkylation; D014450:Electron Transport Complex III / Q000235:genetics / Q000378:metabolism*; D006540:Herbicides / Q000378:metabolism*; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D042301:Sphingomonadaceae / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D000081:Acetamides; D001426:Bacterial Proteins; D006540:Herbicides; C037989:Rieske iron-sulfur protein; D009243:NAD; C078188:2-chloro-N-(ethoxymethyl)-N-(2-methyl-6-(trifluoromethyl)phenyl)acetamide; D010105:Oxygenases; D014450:Electron Transport Complex III