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Functional identification of two novel genes from Pseudomonas sp. strain HZN6 involved in the catabolism of nicotine.

ABSTRACT: Nicotine is a natural alkaloid produced by tobacco plants, and the mechanisms of its catabolism by microorganisms are diverse. In the present study, we reported the mutation, cloning, and identification of two novel genes involved in nicotine degradation from the newly isolated Pseudomonas sp. strain HZN6. Transposon mutagenesis identified a HZN6 mutant in which the nicotine-degrading pathway was blocked at pseudooxynicotine. A 3,874-bp DNA fragment flanking the transposon insertion site was obtained through self-formed adaptor PCR. Two open reading frames (designated pao and sap) were analyzed, and the deduced amino acid sequences shared 29% identity with 6-hydroxy-l-nicotine oxidase from Arthrobacter nicotinovorans and 49% identity with an aldehyde dehydrogenase from Bartonella henselae. Both pao and sap were cloned and functionally expressed in recombinant Escherichia coli BL21. The pao gene encoded a novel pseudooxynicotine amine oxidase with noncovalently bound flavin adenine dinucleotide (FAD) and exhibited substrate specificity removing the methylamine from pseudooxynicotine with the formation of 3-succinoylsemialdehyde-pyridine and hydrogen dioxide. The sap gene encoded a NADP(+)-dependent 3-succinoylsemialdehyde-pyridine dehydrogenase that catalyzed the dehydrogenation of 3-succinoylsemialdehyde-pyridine to 3-succinoyl-pyridine. Genetic analyses indicated that the pao gene played an essential role in nicotine or pseudooxynicotine mineralization in strain HZN6, whereas the sap gene did not. This study provides novel insight into the nicotine-degrading mechanism at the genetic level in Pseudomonas spp.

SUBMITTER: Qiu J

PROVIDER: S-EPMC3302611 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Functional identification of two novel genes from Pseudomonas sp. strain HZN6 involved in the catabolism of nicotine.

Qiu Jiguo J Ma Yun Y Wen Yuezhong Y Chen Liansheng L Wu Lifei L Liu Weiping W

Applied and environmental microbiology 20120120 7

Nicotine is a natural alkaloid produced by tobacco plants, and the mechanisms of its catabolism by microorganisms are diverse. In the present study, we reported the mutation, cloning, and identification of two novel genes involved in nicotine degradation from the newly isolated Pseudomonas sp. strain HZN6. Transposon mutagenesis identified a HZN6 mutant in which the nicotine-degrading pathway was blocked at pseudooxynicotine. A 3,874-bp DNA fragment flanking the transposon insertion site was obt ...[more]

PMID: 22267672

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Project description:The gene loci fcs, encoding feruloyl coenzyme A (feruloyl-CoA) synthetase, ech, encoding enoyl-CoA hydratase/aldolase, and aat, encoding beta-ketothiolase, which are involved in the catabolism of ferulic acid and eugenol in Pseudomonas sp. strain HR199 (DSM7063), were localized on a DNA region covered by two EcoRI fragments (E230 and E94), which were recently cloned from a Pseudomonas sp. strain HR199 genomic library in the cosmid pVK100. The nucleotide sequences of parts of fragments E230 and E94 were determined, revealing the arrangement of the aforementioned genes. To confirm the function of the structural genes fcs and ech, they were cloned and expressed in Escherichia coli. Recombinant strains harboring both genes were able to transform ferulic acid to vanillin. The feruloyl-CoA synthetase and enoyl-CoA hydratase/aldolase activities of the fcs and ech gene products, respectively, were confirmed by photometric assays and by high-pressure liquid chromatography analysis. To prove the essential involvement of the fcs, ech, and aat genes in the catabolism of ferulic acid and eugenol in Pseudomonas sp. strain HR199, these genes were inactivated separately by the insertion of omega elements. The corresponding mutants Pseudomonas sp. strain HRfcsOmegaGm and Pseudomonas sp. strain HRechOmegaKm were not able to grow on ferulic acid or on eugenol, whereas the mutant Pseudomonas sp. strain HRaatOmegaKm exhibited a ferulic acid- and eugenol-positive phenotype like the wild type. In conclusion, the degradation pathway of eugenol via ferulic acid and the necessity of the activation of ferulic acid to the corresponding CoA ester was confirmed. The aat gene product was shown not to be involved in this catabolism, thus excluding a beta-oxidation analogous degradation pathway for ferulic acid. Moreover, the function of the ech gene product as an enoyl-CoA hydratase/aldolase suggests that ferulic acid degradation in Pseudomonas sp. strain HR199 proceeds via a similar pathway to that recently described for Pseudomonas fluorescens AN103.

Dataset Information

Functional identification of two novel genes from Pseudomonas sp. strain HZN6 involved in the catabolism of nicotine.

Publications

Functional identification of two novel genes from Pseudomonas sp. strain HZN6 involved in the catabolism of nicotine.

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