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PubMed2006

Removal of 2,4-dichlorophenol and pentachlorophenol from waters by sorption using coal fly ash from a Portuguese thermal power plant.

Chlorophenols are one of the most important groups of priority pollutants, due to their high toxicity, mutagenicity and carcinogenicity. Although activated carbon has been the preferred choice for the removal of such pollutants from wastewaters, the search for cheaper alternative sorbents became common in the last years. Fly ash, a by-product from coal burning power plants, has a surface composition that may enable the sorption of specific organic compounds. Therefore, this feasibility study presents the optimization of the operating parameters of a fixed-bed column containing fly ash particles, percolated by aqueous solutions of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) with concentrations of 1 and 100 microg/ml. Both chlorophenols were analysed by gas chromatography with electron capture detection (GC-ECD), after solid-phase microextraction (SPME), with limits of detection (LODs) of 7.28 microg/l for 2,4-DCP and 1.76 microg/l for PCP. Removal efficiencies above 99% were obtained for an initial concentration of 10 microg/ml of chlorophenols. Column saturation was achieved after 7h of continuous operation for 2,4-DCP and 10h for the PCP for feed levels of 10 microg/ml. Fly ash exhibited more affinity towards the sorption of PCP, in comparison to 2,4-DCP.

Adsorption↗
PubMed2006

Degradation of pentachlorophenol in contaminated soil suspensions by potassium monopersulfate catalyzed oxidation by a supramolecular complex between tetra(p-sulfophenyl)porphineiron(III) and hydroxypropyl-beta-cyclodextrin.

To enhance the catalytic oxidation of pentachlorophenol (PCP) in contaminated soil suspensions using tetra(p-sulfophenyl)porphineiron(III) (Fe(III)-TPPS) as a catalyst and potassium monopersulfate (KHSO(5)) as the single-oxygen donor, the effect of added hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was examined. At pH 4 and 6, the percentage of PCP disappearance increased substantially in the presence of HP-beta-CD. In addition, the self-degradation of Fe(III)-TPPS was significantly retarded in the presence of HP-beta-CD. This retarded self-degradation can be attributed to the stabilization of Fe(III)-TPPS via the formation of a supramolecular complex with HP-beta-CD. The kinetic constant for the self-degradation of Fe(III)-TPPS in the presence of HP-beta-CD at pH 6 was much smaller than that at pH 4, indicating that Fe(III)-TPPS is more stable at pH 6. Thus, the amount of Fe(III)-TPPS, KHSO(5) and HP-beta-CD required to degrade PCP in contaminated soil suspensions was optimal at pH 6. When PCP-contaminated soil suspensions were treated under the optimized conditions, 12-18% and 24-28% of the PCP was mineralized to CO(2) in the absence and presence of HP-beta-CD, respectively. These results show that the presence of HP-beta-CD in the Fe(III)-TPPS/KHSO(5) catalytic system is effective in enhancing the degradation of PCP in contaminated soil suspensions.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

Pentachlorophenol treatment in vivo elevates point mutation rate in zebrafish p53 gene.

Pentachlorophenol (PCP), a probable human carcinogen, has been heavily used as an aseptic and a biocide throughout the world, and is widely present in the environment. Recent survey in Germany revealed that the average PCP amount in the urine of general German populations was 1.04 microg/L while the peak concentration could reach up to 19.1 microg/L. PCP was reported to cause DNA damage, but whether it can be involved in inducing point mutations in genome is unknown. To determine the genotoxicity of PCP on vertebrate, we first performed acute toxicity test on zebrafish for the effect of PCP exposure. The LC50 values of zebrafish exposed to PCP at 24, 48, 72 and 96 h were determined to be 0.196, 0.130, 0.130 and 0.130 mg/L, respectively. We then treated zebrafish with PCP for 10 days at 0 (control), 0.5, 5 and 50 microg/L, respectively, to determine whether PCP could be involved in inducing point mutations. Employing denaturing high-performance liquid chromatography analysis and DNA sequencing, we demonstrated that exposure of PCP to zebrafish at a concentration as low as 5 microg/L for 10 days elevates point mutation rate in p53 gene in liver cells. This is the first direct evidence revealing that PCP can elevate point mutation rate in the vertebrate genomes. The result implies PCP might be involved in carcinogenesis by elevating point mutation rate in the somatic genomes.

Animals↗
PubMed2004

Degradation of pentachlorophenol in cyclodextrin extraction effluent using a photocatalytic process.

This work evaluates a process for the elimination of pentachlorophenol (PCP) from effluents provided by a cyclodextrin-assisted flushing of contaminated soils. The effectiveness of photocatalytic degradation of PCP in several cyclodextrin (CD) solutions was evaluated using TiO2 as a photocatalyst. Effects of CD type on PCP degradation rate were studied at two pH values. A similar effect was observed for all CDs used on degradation rate of PCP and the decay of PCP was found to be less extensive at pH 11 than at pH 7. The kinetic orders of the photocatalytic reactions of PCP for all of the solutions have been determined. The first-order rate constants were found to be 0.0884, 0.0362, 0.0197 and 0.0053 min(-1) in CD solutions, respectively, at 0, 1, 2 and 5 mmol l(-1) of CD. Batch experiments were performed in order to study the CD extraction enhancement of PCP previously adsorbed on soil. The results show that the removal capacity of PCP from soil increases with CD concentration (from 0 to 5 mmol l(-1)). When the CD concentration was 5 mmol l(-1), an extraction of about 70% of PCP adsorbed on soil was observed, whereas only 37% was removed when water was used as the flushing solution. The optimal conditions for such a coupled method depend on the nature and concentration of the extracting agent and also on the photocatalytic experimental conditions. This work revealed that the coupling of cyclodextrin-enhanced solubilization and photocatalytic treatment is a promising method for contaminated soil remediation.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

Evaluation of dissipation mechanisms by Lolium perenne L, and Raphanus sativus for pentachlorophenol (PCP) in copper co-contaminated soil.

Though phytoremediation is widely studied in remediation of metal contaminated soils or organic contaminated soils, little information is available regarding the effectiveness and processes of phytoremediation of sites co-contaminated with organic and metal pollutants. Sites co-contaminated with organic and metal pollutants are common and considered to be a more complex problem as the two components often cause a synergistic effect on cytotoxicity as measured both by growth inhibition and colony-forming ability. In this paper, the dissipation mechanisms for pentachlorophenol (PCP) in copper co-contaminated soil by Lolium perenne L, and Raphanus sativus was investigated in a greenhouse experiment by monitoring the growth response of plants, evaluating the removal efficiency of extractable PCP, differentiating PCP residuals in strongly and loosely adhering rhizosphere soils, and analyzing the microbial activity in the rhizosphere. In copper co-contaminated soil with the initial PCP concentration of 50 mg/kg, plants grew better with the increment of soil Cu level (0, 150, 300 mg/kg), which implied that combinations of inorganic and organic pollutants sometimes exerted antagonistic effects on plant cytotoxicity. The observed higher PCP dissipation in soil spiked with 50 mg/kg PCP in the presence of Cu and the less difference of PCP residual between strongly and loosely adhering soils further suggests the occurrence of Cu-PCP interaction and the enhanced degradation and mass flow are two possible explanations. In copper co-contaminated soil with the initial PCP concentration of 100 mg/kg, however, both plant growth and microbial activity were inhibited with the increment of soil Cu level. The lowered degrading activity of microorganisms and the reduced mass flow were probably responsible for the significantly lower levels of PCP dissipation in copper co-contaminated soil. These results showed that remediation of sites co-contaminated with organic and metal pollutants is a complex problem and a more thorough understanding of the extent and mechanisms by which metals inhibit organic degradation is needed to develop phytoremediation of co-contaminated sites.

Biodegradation, Environmental↗
PubMed2006

Bioavailability and toxicity of pentachlorophenol in contaminated soil evaluated on coelomocytes of Eisenia andrei (Annelida: Lumbricidae).

Pentachlorophenol (PCP) is widely distributed and highly persistent in soil, and represents a threat to the health of ecosystems. The present study aimed to assess the toxicity and bioavailability of PCP in soils as a function of different aging periods with the attempt to select a good toxicological assay for Eisenia andrei Bouché (Annelida: Lumbricidae). The experiments were performed on soil contaminated with PCP at 15 and 150ppm. After different aging periods (20, 60 and 120 days from spiking), bioavailability and toxicity were evaluated on E. andrei kept for 7 and 14 days in treated soils. The actual bioavailability decreased in relation to the aging for both PCP concentrations. No membrane damage was observed on coelomocytes collected by ethanol extrusion. Modifications in distribution of coelomocyte subpopulations were detected by flow cytometry on samples aged for 60 and 120 days at 150ppm PCP contamination. The reduction of lysosomal membrane stability, measured by neutral red retention time, was observed in all treatments. Worm mortality increased with aging in soils spiked with 150ppm of PCP. In conclusion, aging did not seem to reduce PCP cytotoxicity. This is the first report on in vivo toxicity of PCP evaluated on coelomocytes of E. andrei using different assays.

Animals↗
PubMed2003

Aqueous chemistry and interactive effects on non-ionic surfactant and pentachlorophenol sorption to soil.

Non-ionic surfactant addition was investigated as a method to remediate pentachlorophenol (PCP) contaminated soil. The goal was to quantify surfactant (Tergitol NP-10 (TNP10)) and PCP sorption to soil and their interactive effects under varying pH, ionic strength, and soil conditions. Up to 16,700 mg/kg of TNP10 partitioned to soil, with increasing sorption far above the critical micelle concentration (CMC) and with greater amounts of PCP present. Approximately 40-45 times more TNP10 and 20-30 times more PCP sorbed to the finer soil with higher organic matter content. Aqueous TNP10 concentrations well above the CMC (>/=5500 mg/L) were required to enhance PCP desorption from the soil. As pH increased by 0.5-0.85 units, TNP10 sorption decreased by 14-25% and PCP sorption as measured by the log of the equilibrium partition coefficient decreased by 1-1.5. A lower ionic strength of 0.03 versus 0.112 M increased PCP desorption from contaminated soil by 5-17% in the presence of TNP10. This work is relevant to designing ex situ soil washing or surfactant-aided PCP remediation.

Adsorption↗
PubMedDate not supplied

Modelling the dynamics of pentachlorophenol bioavailability in column experiments.

The aqueous-phase concentration of an organic pollutant found in a subsurface environment is often assumed to be its bioavailable concentration. However, the aqueous-phase concentration does not adequately reflect the dynamics of contaminant availability to microbes in flow-through systems. This paper assesses the effects of interacting processes such as sorption, biodegradation, and transport on contaminant bioavailability, and the fraction of the bioavailable contaminant that is taken up by microbes. The evolution of the bioavailable and uptake fractions is studied in two ways. Firstly, column experiments are conducted in which the introduced contaminant (pentachlorophenol, PCP) can flow through the columns, be consumed by microorganisms, or be sorbed by a solid matrix. Secondly, a phenomenological model (Flow/Sink/Reservoir model) that illustrates the dynamic nature of bioavailability and quantifies the uptake fraction is developed, based on a flow balance. Results show that after 60 h of sorption-limited bioavailability, the microorganisms induce desorption, so that the sorbed pool becomes bioavailable and bioavailability is limited by the PCP injection rate. A conclusion is drawn that the aqueous-phase concentration is a poor indicator of contaminant bioavailability to microbes.

Adsorption↗
PubMed2005

Non-ionic surfactant flushing of pentachlorophenol from NAPL-contaminated soil.

Column studies were conducted to assess the suitability of a non-ionic surfactant Tergitol NP-10 (TNP10) for washing pentachlorophenol (PCP) from soil and non-aqueous phase liquids (NAPLs). Flushing of 50 and 200 pore volumes of 5 g/L TNP10 was required to exhaust the surfactant sorption capacity of the soil and soil plus NAPL, respectively. The sorption of surfactant to the soil in the columns was four times greater than the quantity previously observed in batch tests. Flushing with 5 g/L TNP10 removed 71-79% of the 200mg/kg soil-sorbed PCP after 160 pore volumes compared to 0.7-2% PCP removal without surfactant. In columns additionally containing 0.2% and 0.4% PCP-contaminated heavy oil NAPL, the PCP removal efficiency after flushing 200 pore volumes of 5g/L TNP10 was nearly 100%. Therefore, removal of the PCP was more efficient in the NAPL-containing columns, potentially due to competition of the NAPL for PCP sorption sites. Rate-limited desorption of PCP and TNP10 likely occurred.

Adsorption↗
PubMed2005

Coupling enhanced water solubilization with cyclodextrin to indirect electrochemical treatment for pentachlorophenol contaminated soil remediation.

This study undertakes to examine, at laboratory scale, the technical feasibility, mechanisms and performances provided by coupling the enhanced flushing abilities of cyclodextrin solutions for pentachlorophenol (PCP) removal from contaminated soil with indirect electrochemical treatment for the final disposal of soil extract solutions containing high PCP loads (0.77mmolL(-1)). The hydroxypropyl-beta-cyclodextrin (HPCD) solution increased the aqueous concentration of PCP in soil extract effluents to as much as 3.5 times the concentrations obtained during the water flush of the soil. PCP was treated with electrochemically generated Fenton's reagent in an aqueous medium. The increase in PCP water solubility in the presence of HPCD is balanced by the corresponding decrease in PCP degradation rate under indirect electrochemical treatment. This is due to the high carbon content (HPCD and dissolved natural organic matter) in the soil extract solutions, which compete for the non-selective hydroxyl radical reaction to PCP. However, our results indicate that HPCD has a beneficial effect on the degradation rates of PCP. This relative improvement in PCP degradation could be explained by the formation of the ternary complex (PCP-cyclodextrin-iron) which may direct hydroxyl reaction to PCP and which would, in any case, justify the use of a Fenton -like process for the final treatment of soil extract solutions. Total disappearance of PCP and 90% abatement of the chemical oxygen demand were achieved within an 11h electrolysis treatment time. Elucidation of the PCP degradation pathway indicates that after successive PCP hydroxylations, oxidative opening of the PCP aromatic ring quickly occurred, leading to small unstable non-chlorinated or partially chlorinated short chain carboxylic acids, such as monochloroacetic and dichloromaleic acid. Determination of the concentration of these acids shows that indirect electrochemical treatment leads to oxalic acid accumulation in aqueous solutions treated. A decrease in toxicity was observed at the end of the treatment time.

Carbon↗
PubMed1986

Catabolism of pentachlorophenol by a Flavobacterium sp.

The pathway employed for pentachlorophenol (PCP) degradation by an aerobic, chlorophenol-utilizing Flavobacterium sp. was initiated by conversion of PCP to tetrachloro-p-hydroquinone (TCH). 18O labelling experiments demonstrated that the first dechlorination, where a hydroxyl replaced the chlorine at PCP ring position number 4, involved a hydrolytic reaction. Then two reductive dechlorinations of TCH followed to yield firstly trichlorohydroquinone (TrCH) and then 2,6-dichlorohydroquinone (DCH). Thus, the initial steps in catabolism of PCP by the Flavobacterium were: PCP----TCH----TrCH.

Chlorine↗
PubMed2004

Distribution of pentachlorophenol in phospholipid bilayers: a molecular dynamics study.

Molecular dynamics computer simulations of pentachlorophenol (PCP) in palmitoyl-oleoyl-phosphatidylethanolamine and palmitoyl-oleoyl-phosphatidylcholine lipid bilayers were carried out to investigate the distribution of PCP and the effects of PCP on the phospholipid bilayer structure. Starting from two extreme starting structures, including PCP molecules outside the lipid bilayer, the PCP distribution converges in simulations of up to 50 ns. PCP preferentially occupies the region between the carbonyl groups and the double bonds in the acyl chains of the lipid molecules in the bilayer. In the presence of PCP, the lipid chain order increases somewhat in both chains, and the average tilt angle of the lipid chains decreases. The increase in the lipid chain order in the presence of PCP was more pronounced in the palmitoyl-oleoyl-phosphatidylcholine bilayer compared to the palmitoyl-oleoyl-phosphatidylethanolamine bilayer. The number of trans conformations of lipid chain dihedrals does not change significantly. PCP aligns parallel to the alkyl chains of the lipid to optimize the packing in the dense ordered chain region of the bilayer. The hydroxyl group of PCP forms hydrogen bonds with both water and lipid oxygen atoms in the water/lipid interface region.

Computer Simulation↗
PubMed1990

Adsorption to dipalmitoylphosphatidylcholine membranes in gel and fluid state: pentachlorophenolate, dipicrylamine, and tetraphenylborate.

UNLABELLED: We measured the dependence of electrophoretic mobility of dipalmitoylphosphatidylcholine (DPPC) vesicles on the aqueous concentration of negatively charged ions of pentachlorophenol (PCP), dipicrylamine (DPA), and tetraphenylborate (TPhB). The objective was to determine how the physical state of hydrocarbon chains of lipids affects adsorption of lipophilic ions. The studies were done at 25 and 42 degrees C to determine adsorption properties of DPPC membrane in the gel and fluid state, respectively. From the analysis of zeta-potential isotherms in terms of Langmuir-Stern-Grahame model we obtained the association constant, K, the area of the adsorption site, Ps, and the linear partition coefficient, beta. RESULTS: K, (x 10(4)M-1): K(gel): PCP (0.49 +/- 0.28), DPA (25 +/- 10), TPhB (31 +/- 10); K(fluid): PCP (4.5 +/- 0.9), DPA (74 +/- 21), TPhB (59 +/- 14); Ps, (nm2): Ps(gel): PCP (5.4 +/- 2.3), DPA (5.9 +/- 2), TPhB (5.0 +/- 1.7); Ps(fluid): PCP (4.5 +/- 0.4), DPA (5.2 +/- 0.4), TPhB (4.1 +/- 0.2); beta, (x 10(-5) m): beta(gel): PCP (0.15 +/- 0.09), DPA (7.1 +/- 0.3), TPhB (10 +/- 7); beta(fluid): PCP (1.7 +/- 0.3), DPA (24 +/- 7), TPhB (24 +/- 6). It was interesting to find that the adsorption site area for PCP, DPA, and TPhB were very similar for both the gel and fluid membranes; also, the areas were independent of the size and molecular structure of the adsorbing species. Using a simple discrete charge model the adsorption site areas for all species were consistent with a dielectric constant of 8-10 and with an ion adsorption depth of 0.4-0.6 nm below the water/dielectric interface. The delta delta G0 = delta G0(gel) - delta G0(fluid) was found to be about twice as large for PCP than for DPA and TPhB. This indicates that PCP will be significantly more adsorbed in the fluid and disordered regions of biomembranes, whereas the distribution of DPA and TPhB is expected to be relatively more even.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Domains and anomalous adsorption isotherms of dipalmitoylphosphatidylcholine membranes and lipophilic ions: pentachlorophenolate, tetraphenylborate, and dipicrylamine.

Dipalmitoylphosphatidylcholine (DPPC) vesicles acquire negative surface charge on adsorption of negatively charged pentachlorophenolate (PCP-), and lipophilic ions tetraphenylborate (TPhB-), and dipicrylamine (DPA-). We have obtained (a) zeta-potential isotherms from the measurements of electrophoretic mobility of DPPC vesicles as a function of concentration of the adsorbing ions at different temperatures (25-42 degrees C), and (b) studied the effect of PCP- on gel-to-fluid phase transition by measuring the temperature dependence of zeta-potential at different PCP- concentrations. The zeta-potential isotherms of PCP- at 25, 32, and 34 degrees C correspond to adsorption to membrane in its gel phase. At 42 degrees C the zeta-potential isotherm corresponds to membrane in its fluid phase. These isotherms are well described by a Langmuir-Stern-Grahame adsorption model proposed by McLaughlin and Harary (1977. Biochemistry. 15:1941-1948). The zeta-potential isotherm at 37 degrees C does not follow the single-phase adsorption model. We have also observed anomalous adsorption isotherms for lipophilic ions TPhB- and DPA- at temperatures as low as 25 degrees C. These isotherms demonstrate a gel-to-fluid phase transition driven by ion adsorption to DPPC membrane during which the membrane changes from weakly to a strongly adsorbing state. The anomalous isotherm of PCP- and the temperature dependence of zeta-potential can be described by a two-phase model based on the combination of (a) Langmuir-Stern-Grahame model for each phase, (b) the coexistence of gel and fluid domains, and (c) depression of gel-to-fluid phase transition temperature by PCP-. Within the anomalous region the magnitude of zeta-potential rapidly increases concentration of adsorbing species, which was characterized in terms of a Esin-Markov coefficient. This effect can be exploited in membrane-based devices. Comments are also made on the possible effect of PCP, as an uncoupler, in energy transducing membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Different cell death mechanisms and gene expression in human cells induced by pentachlorophenol and its major metabolite, tetrachlorohydroquinone.

Pentachlorophenol (PCP) and its salt are used extensively as biocide and wood preservative. Due to improper disposal, PCP has become an environmental pollutant and is now considered to be ubiquitos. Metabolic studies carried out in rodents or human liver homogenate have indicated that PCP undergoes oxidative dechlorination to form tetrachlorohydroquinone (TCHQ). The cytotoxicity, cell death mechanisms and gene expression of PCP and TCHQ are investigated in human liver and bladder cells and show that TCHQ induces apoptosis and DNA genomic fragmentation in bladder cells but not liver cells. No apoptotic features could be induced by treatment of PCP in both cell lines. The concentrations of PCP required to cause 50% cell death in T-24 and Chang liver cells were 5-10-fold greater than the concentrations of TCHQ. Several gene products are important in controlling the apoptotic and necrotic processes. Of these, hsp 70, CAS, bcl-2 and bax were studied. The expression of the hsp70 gene increased significantly (2-3-fold) in cells treated with TCHQ. However, no significant change was found in the cells treated with PCP. The expression of CAS gene decreased significantly in T-24 cells treated with both TCHQ and PCP. Whereas, no significant change was found in Chang liver cells with the same treatment. In addition, the expression of the bcl-2/bax protein decreased significantly in these two cell lines treated with TCHQ but not PCP.

Apoptosis↗
PubMed2000

Mechanism of the synergistic cytotoxicity between pentachlorophenol and copper-1,10-phenanthroline complex: the formation of a lipophilic ternary complex.

When non- or sub-toxic levels of pentachlorophenol (PCP) and bis-(1, 10-phenanthroline)cupric complex, Cu(II)(OP)(2), were combined, a remarkable synergistic toxicity was observed as indicated by growth inhibition and bacterial inactivation. Similar synergistic cytotoxic effects were observed with other polychlorinated phenols and other positively charged cupric complexes. The synergism observed for these chemicals and similar reactive pairs of chemicals was found to be due to the formation of lipophilic ternary complexes which facilitated copper transport into the bacterial cells. The formation of ternary complexes of similar lipophilic character could be of relevance as a general mechanism of toxicity.

Biological Transport↗
PubMed2001

Characterization of metabolic activation of pentachlorophenol to quinones and semiquinones in rodent liver.

Pentachlorophenol (PCP), a widely used biocide, induces liver tumors in mice but not in rats. Metabolic activation of PCP to chlorinated quinones and semiquinones in liver cytosol from Sprague-Dawley rats and B6C3F1 mice was investigated in vitro (1) with microsomes in the presence of either beta-nicotinamide adenine dinucleotide phosphate (NADPH) or cumene hydroperoxide (CHP), (2) with CHP in the absence of microsomes, and (3) with horseradish peroxidase (HRP) and H2O2. Mono-S- and multi-S-substituted adducts of tetrachloro-1,4-benzoquinone (Cl4-1,4-BQ) and Cl4-1,2-BQ and their corresponding semiquinones [i.e. tetrachloro-1,4-benzosemiquinone (Cl4-1,4-SQ) and tetrachloro-1,2-benzosemiquinone (Cl4-1,2-SQ)] were measured by gas chromatography-mass spectrometry (GC-MS). Qualitatively, the metabolites of PCP were the same in both rats and mice for all activation systems. Induction of PCP metabolism by either 3MC or PB-treated microsomes was observed in NADPH- but not in CHP-supported systems. In rats, the amount of induction was comparable with either 3MC or PB. 3MC was a stronger inducer than PB in mice and also induced a greater amount of metabolism than in rats. This suggests that induction of specific P450 isozymes may play a role in the toxicity of PCP to mice. Both HRP/H2O2 and CHP led to production of the full spectrum of chlorinated quinones and semiquinones, confirming the direct oxidation of PCP. CHP (with or without microsomes) converted PCP into much greater quantities of quinones and semiquinones than did microsomal P450/NADPH or HRP/H2O2 in both species. This implies that, under conditions of oxidative stress, endogenous lipid hydroperoxides may increase PCP metabolism sufficiently to enhance the toxicity and carcinogenicity of PCP.

Animals↗
PubMed1999

PcpA, which is involved in the degradation of pentachlorophenol in Sphingomonas chlorophenolica ATCC39723, is a novel type of ring-cleavage dioxygenase.

The pentachlorophenol (PCP) mineralizing bacterium Sphingomonas chlorophenolica ATCC39723 degrades PCP via 2,6-dichlorohydroquinone (2,6-DCHQ). The pathway converting PCP to 2,6-DCHQ has been established previously; however, the pathway beyond 2,6-DCHQ is not clear, although it has been suggested that a PcpA plays a role in 2, 6-DCHQ conversion. In this study, PcpA expressed in Escherichia coli was purified to homogeneity and shown to have novel ring-cleavage dioxygenase activity in conjunction with hydroquinone derivatives, and converting 2,6-DCHQ to 2-chloromaleylacetate.

Amino Acid Sequence↗