Branching of the p-nitrophenol (PNP) degradation pathway in burkholderia sp. Strain SJ98: Evidences from genetic characterization of PNP gene cluster

Background: Two-subunit hydroquinone 1,2-dioxygenase PnpCD is the ring cleavage enzyme in para-nitrophenol catabolism. Results:The structures of apo-PnpCD and its complex with substrate analog (hydroxybenzonitrile) were determined. Conclusion: PnpCD reveals a new class of Fe 2ϩ -dependent dioxygenases. Significance: PnpCD structure contains a pseudo "cupin" and a novel iron metallocenter in the catalytic PnpD, which adds to understanding of the ring cleavage mechanism of dioxygenases.

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“…5B). Combined with the previous reports (9,11,12), it can be inferred that the polymeric status (heterotetramer) of HQDOs is highly conserved.…”

Section: Structure Of Apo-pnpcd Pnpcd-fe 3ϩsupporting

confidence: 68%

Crystal Structure of PnpCD, a Two-subunit Hydroquinone 1,2-Dioxygenase, Reveals a Novel Structural Class of Fe2+-dependent Dioxygenases

Liu

Zhang

et al. 2015

Journal of Biological Chemistry

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“…To date, two typical HQ ring cleavage enzymes, including the LinE-like single-subunit HQ dioxygenase (41,42) and the HapCD-like two-subunit HQ dioxygenase (14,35,43), have been reported in bacterial catabolism of aromatics. Previously, strain RKJ300 was reported to degrade 2C4NP with initial formation of CHQ, which was further degraded via an HQ pathway (Fig.…”

Section: Discussionmentioning

confidence: 99%

A Two-Component para -Nitrophenol Monooxygenase Initiates a Novel 2-Chloro-4-Nitrophenol Catabolism Pathway in Rhodococcus imtechensis RKJ300

Min

Zhang

Zhou

2016

Appl Environ Microbiol

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bRhodococcus imtechensis RKJ300 (DSM 45091) grows on 2-chloro-4-nitrophenol (2C4NP) and para-nitrophenol (PNP) as the sole carbon and nitrogen sources. In this study, by genetic and biochemical analyses, a novel 2C4NP catabolic pathway different from those of all other 2C4NP utilizers was identified with hydroxyquinol (hydroxy-1,4-hydroquinone or 1,2,4-benzenetriol [BT]) as the ring cleavage substrate. Real-time quantitative PCR analysis indicated that the pnp cluster located in three operons is likely involved in the catabolism of both 2C4NP and PNP. The oxygenase component (PnpA1) and reductase component (PnpA2) of the two-component PNP monooxygenase were expressed and purified to homogeneity, respectively. The identification of chlorohydroquinone (CHQ) and BT during 2C4NP degradation catalyzed by PnpA1A2 indicated that PnpA1A2 catalyzes the sequential denitration and dechlorination of 2C4NP to BT and catalyzes the conversion of PNP to BT. Genetic analyses revealed that pnpA1 plays an essential role in both 2C4NP and PNP degradations by gene knockout and complementation. In addition to catalyzing the oxidation of CHQ to BT, PnpA1A2 was also found to be able to catalyze the hydroxylation of hydroquinone (HQ) to BT, revealing the probable fate of HQ that remains unclear in PNP catabolism by Gram-positive bacteria. This study fills a gap in our knowledge of the 2C4NP degradation mechanism in Gram-positive bacteria and also enhances our understanding of the genetic and biochemical diversity of 2C4NP catabolism.C hloronitrophenols, such as 2-chloro-4-nitrophenol (2C4NP), 4-chloro-2-nitrophenol (4C2NP), and 2-chloro-5-nitrophenol (2C5NP), with high toxicity to human beings and animals have been widely used in the pharmaceutical, agricultural, and chemical industries (1). The natural formation of chloronitrophenols is rare, and most of these compounds in the environment result from anthropogenic activity. Apparently, the introduction of chloronitrophenols into the environment has selected microorganisms to develop the ability to degrade these compounds. So far, several strains able to degrade chloronitrophenols have been isolated, including the 2C4NP-degrading strains Burkholderia sp. strain SJ98 (2), Burkholderia sp. strain RKJ800 (3), Rhodococcus imtechensis RKJ300 (4), and Arthrobacter sp. strain SJCon (5), the 4C2NP-degrading strain Exiguobacterium sp. strain PMA (6), and the 2C5NP-degrading strain Ralstonia eutropha JMP134 (7).Structurally, chloronitrophenols are chemical analogs of nitrophenols. The microbial degradation of nitrophenols has been extensively investigated at genetic and biochemical levels (8-13). In contrast to nitrophenols, chloronitrophenols are more resistant to microbial degradation due to the simultaneous existence of electron-withdrawing chloro and nitro groups, and the knowledge of their microbial degradation is thus very limited. Previously, the partially purified enzymes involved in meta-nitrophenol catabolism were reported to be able to catalyze 2C5NP transformation in Ralstonia eutroph...

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“…Other homologs of HapE protein are also present in Burkholderia sp., Sphingomonas sp., Azospirillum amazonense , and in Brachymonas petroleovorans . The enzyme is an oxidoreductase that used NADP nucleotides as electron acceptors [11, 12, 66]. It belongs to the NAD(P)-dependent aldehyde dehydrogenase superfamily, a group of enzymes with an important role either in detoxification reactions or in other metabolic pathways.…”

Section: Degradation Of Hydroquinone Under Aerobic Conditionsmentioning

confidence: 99%

Hydroquinone: Environmental Pollution, Toxicity, and Microbial Answers

Enguita

Leitão

2013

BioMed Research International

186

106

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Hydroquinone is a major benzene metabolite, which is a well-known haematotoxic and carcinogenic agent associated with malignancy in occupational environments. Human exposure to hydroquinone can occur by dietary, occupational, and environmental sources. In the environment, hydroquinone showed increased toxicity for aquatic organisms, being less harmful for bacteria and fungi. Recent pieces of evidence showed that hydroquinone is able to enhance carcinogenic risk by generating DNA damage and also to compromise the general immune responses which may contribute to the impaired triggering of the host immune reaction. Hydroquinone bioremediation from natural and contaminated sources can be achieved by the use of a diverse group of microorganisms, ranging from bacteria to fungi, which harbor very complex enzymatic systems able to metabolize hydroquinone either under aerobic or anaerobic conditions. Due to the recent research development on hydroquinone, this review underscores not only the mechanisms of hydroquinone biotransformation and the role of microorganisms and their enzymes in this process, but also its toxicity.

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Branching of the p-nitrophenol (PNP) degradation pathway in burkholderia sp. Strain SJ98: Evidences from genetic characterization of PNP gene cluster

Cited by 30 publications

References 26 publications

Crystal Structure of PnpCD, a Two-subunit Hydroquinone 1,2-Dioxygenase, Reveals a Novel Structural Class of Fe2+-dependent Dioxygenases

Crystal Structure of PnpCD, a Two-subunit Hydroquinone 1,2-Dioxygenase, Reveals a Novel Structural Class of Fe2+-dependent Dioxygenases

A Two-Component para -Nitrophenol Monooxygenase Initiates a Novel 2-Chloro-4-Nitrophenol Catabolism Pathway in Rhodococcus imtechensis RKJ300

Hydroquinone: Environmental Pollution, Toxicity, and Microbial Answers

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