• Title/Summary/Keyword: Polychlorinated Biphenyls

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Genetic and Biochemical Characterization of the Biphenyl Dioxygenase from Pseudomonas sp. Strain B4

  • Rodarie, David;Jouanneau, Yves
    • Journal of Microbiology and Biotechnology
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    • v.11 no.5
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    • pp.763-771
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    • 2001

  • Biphenyl dioxygenase (BPDO), which catalyzes the first step in the bacterial degradation of biphenyl and polychlorinated biphenyls, was characterized in Pseudomonas sp. B4. The bphA locus containing the four structural genes encoding BPDO were cloned and sequenced. A regulatory gene as well as a putative regulatory sequence were identified upstream of this locus. A transposase-like gene was found within a 1-kb region further upstream, thereby suggesting that the bphA locus may be carried on a transposable element. The three components of the BPDO enzyme have been separately overexpressed and purified from E. coli. The ferredoxin and terminal dioxygenase components showed biochemical properties comparable to those of two previously characterized BPDOs, whereas the ferredoxin reductase exhibited an unusually high lability. The substrate selectivity of BPDO was examined in vivo using resting cell assays performed with mixtures of selected polychlorinated biphenyls. The results indicated that para-substituted congeners were the preferred substrates. In vitro studies were carried out on a BPDO complex where the reductase from strain B4 we replaced by the more stable isoform from Comamonas testosteroni B-356. The BPDO enzyme had a specific activity of $0.26{\pm}0.02 {\mu}mol {min^-1}{mg^-1}\;of\;ISP_{BPH}$ with biphenyl as the substrate. The 2,3-, 4,4'-, and 2,4,4'-chlorobiphenyls were converted to single dihydrodiols, while 2,4'-dichlorobiphenyl gave rise to two dihydrodiols. The current data also indicated that 2,4,4'-trichlorobiphenyl was a better substrate than the 4,4'-dichlorinated congener.

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Effects of Polychlorinated Biphenyls and Phenols on the Biosynthesis of 6-Methoxymellein, a Phytoalexin (당근 Phytoalexin 6-Methoxymellein 생합성에 미치는 Polychlorinated Biphenyls 및 Phenol의 영향)

  • Lim, Do-Hyung;Lim, Da-Som;Keum, Young-Soo
    • Korean Journal of Environmental Agriculture
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    • v.35 no.3
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    • pp.216-222
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    • 2016

  • BACKGROUND: Polychlorinated biphenyls (PCBs) are one of the most common environmental contaminants. Because of their recalcitrant properties and long-term toxicity, numerous studies have been performed. The toxicological concerns are focused on endocrinological effects of animal. Several different metabolites have been reported, including hydroxy PCBs, PCB quinones, and methylsulfonyl PCBs from animal tissues. However, details in plants have never been studied. It is well-known that plants can produce phytoalexin in response to chemical, physical, or pathological stress.METHODS AND RESULTS: In this study, the several PCBs and hydroxy derivatives were prepared by chemical syntheses. Their effects on secondary metabolite biosynthesis were determined in carrot roots. The levels of 6-methoxymellein were determined in several different treatments, using gas chromatography-mass spectrometry. In general, the concentration of 6-methoxymellein reached a maximum at 2 days and gradually decreased to trace level at 5 days in control experiments. However, the effects of PCBs or hydroxy derivatives were highly dependent on compounds. For example, the maximum concentrations of 6-methoxymellein were observed at 3 days for 2-hydroxy/4-hydroxybiphenyl, while 3,3',4,4',5-pentachlorobiphenyl and 3,5-dichloro-2-hydroxybiphenyl showed a rapid accumulation within 1 day, followed by rapid dissipation to undetectable levels.CONCLUSION: Biphenyl derivatives were effective elicitor of 6-methoxymellein accumulation. In general, hydroxybiphenyls (phenols) more efficiently induced phytoalexin biosynthesis than those without hydroxy groups. It can be concluded that PCBs or their possible metabolites could change the plant secondary metabolism.

  • https://doi.org/10.5338/KJEA.2016.35.3.23 인용 PDF KSCI KPUBS HTML