Dechlorination of pentachlorophenol by membrane bound enzymes of Rhodococcus chlorophenolicus PCP-I

Uotila, Jussi; Salkinoja‐Salonen, Mirja; Apajalahti, Juha

doi:10.1007/bf00122422

Cited by 61 publications

(45 citation statements)

References 18 publications

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“…The halohydroquinones formed by the para-hydroxylation were further dehalogenated by a soluble halohydroquinone dehalogenase. The results show that M. fortuitum CG-2 dehalogenases are similar to those previously described by us for R. chlorophenolicus PCP-1 and CP-2 (3,4,14,15,28 …”

supporting

confidence: 89%

“…(10), a Mycobacterium sp. (24)(25)(26), and R chlorophenolicus PCP-1 (3,4,28). The present paper demonstrates halophenol parahydroxylation in cell extracts of M. fortuitum CG-2.…”

Section: Discussionmentioning

confidence: 57%

“…Microbial P-450 enzymes are less well understood, and their catalytic properties are only partially characterized. Microbial P-450 enzymes are known to be involved in the dehalogenation of a haloaromatic compound in at least one bacterium, an actinomycete, R. chlorophenolicus PCP-1 (1,28), in which they catalyze the para-hydroxylation of a halophenol, deriving the oxygen required in this reaction from molecular oxygen under aerobic conditions (27). Monooxygenases are an important group of enzymes participating in the hydroxylation of various phenolic compounds (9).…”

Section: Discussionmentioning

confidence: 99%

“…We have shown that the degradation of polychlorophenols, guaiacols, and syringols proceeds through chlorinatedparahydroquinones in three different Rhodococcus chlorophenolicus strains (1,3,12,13,15) and is mediated by a membrane-associated cytochrome P-450 enzyme (28). The product of this para-hydroxylation, TeCH, is further orthohydroxylated by a soluble halohydroquinone dehalogenase (4,14,28).…”

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confidence: 99%

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Characterization of aromatic dehalogenases of Mycobacterium fortuitum CG-2

et al. 1992

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Two different dehalogenation enzymes were found in cell extracts ofMycobacteriumfortuitum CG-2. The first enzyme was a halophenol para-hydroxylase, a membrane-associated monooxygenase that required molecular oxygen and catalyzed the para-hydroxylation and dehalogenation of chlorinated, fluorinated, and brominated phenols to the corresponding halogenated hydroquinones. The membrane preparation with this activity was inhibited by cytochrome P-450 inhibitors and also showed an increase in the A4,, caused by CO. The second enzyme hydroxylated and reductively dehalogenated tetrahalohydroquinones to 1,2,4-trihydroxybenzene. This halohydroquinone-dehalogenating enzyme was soluble, did not require oxygen, and was not inhibited by cytochrome P-450 inhibitors.Actinomycetes are a large and variable group of microorganisms occurring in many habitats, where they take part in the degradation of organic material. Many microbial strains degrading various aromatic pollutants have been isolated from this group. Enzymes so far characterized have been reported to be monooxygenases, hydroxylases, or dioxygenases (for a review, see reference 31). Actinomycetes, including those degrading xenobiotic compounds, have also been shown to be environmentally tenacious, making them a potential source of microorganisms for bioremediation (6,18,29,30).Mycobacterium fortuitum CG-2 was isolated from a tetrachloroguaiacol enrichment culture and shown to degrade several chlorinated phenols, guaiacols, and syringols at micromolar levels (15). Pentachlorophenol (PCP) was shown to be mineralized to CO2, and tetrachloro-para-hydroquinone (TeCH) was detected as an initial intermediate. We have shown that the degradation of polychlorophenols, guaiacols, and syringols proceeds through chlorinatedparahydroquinones in three different Rhodococcus chlorophenolicus strains (1,3,12,13,15) and is mediated by a membrane-associated cytochrome P-450 enzyme (28). The product of this para-hydroxylation, TeCH, is further orthohydroxylated by a soluble halohydroquinone dehalogenase (4,14,28).In this paper, we report on the enzymatic dehalogenation of chlorinated, brominated, and fluorinated phenols and hydroquinones by M. fortuitum CG-2 cell fractions. We show that the halogenated phenols were converted to halogenated para-hydroquinones by a membrane-associated cytochrome P-450 enzyme. The halohydroquinones formed by the para-hydroxylation were further dehalogenated by a soluble halohydroquinone dehalogenase. The results show that M. fortuitum CG-2 dehalogenases are similar to those previously described by us for R. chlorophenolicus PCP-1 and CP-2 (3, 4, 14, 15, 28). MATERIALS AND METHODSBacterial strains and culture conditions. M. fortuitum CG-2 (12, 16) was grown in nutrient broth-yeast extract medium (21) in a gyratory shaker at 28°C. Two-day-old cultures were harvested or induced by the addition of increasing amounts (10 to 50 FtM) of PCP at 24-h intervals and then harvested.Cell fractionation. Cells were harvested by centrifugation (3,000 x g, 10 min, 4°C), resus...

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supporting

confidence: 89%

“…(10), a Mycobacterium sp. (24)(25)(26), and R chlorophenolicus PCP-1 (3,4,28). The present paper demonstrates halophenol parahydroxylation in cell extracts of M. fortuitum CG-2.…”

Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Characterization of aromatic dehalogenases of Mycobacterium fortuitum CG-2

et al. 1992

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“…The strains which we studied are able to degrade several chlorinated phenols, guaiacols, and syringols (2,19,20,24), and they also 0-methylate various chlorinated phenolic compounds (24); however, there are some differences in substrate specificity. The M. chlorophenolicum strains, as well as a strain of M. fortuitum (35), degrade pentachlorophenol via two hydroxylations, followed by reductive dechlorinations, producing 1,2,4-trihydroxybenzene, which is mineralized to CO, (3,4,20,22,24,45,46). Interestingly, these polychlorophenol-degrading strains did not utilize most of the nonhalogenated aromatic compounds which we tested ( Table 4).…”

Section: Resultsmentioning

confidence: 94%