Removal mechanisms of pentachlorophenol in a horizontal-flow anaerobic immobilized biomass reactor (HAIB) inoculated with an indigenous estuarine sediment microbiota: adsorption and biodegradation processes.

Pentachlorophenol (PCP) is a highly toxic and carcinogenic compound with significant environmental impact, necessitating effective treatment technologies. This study evaluates PCP removal mechanisms, including adsorption and biodegradation, during the startup of a horizontal-flow anaerobic immobilized biomass reactor (HAIB), and examines the impact of PCP concentration on microbial diversity using denaturing gradient gel electrophoresis (DGGE). The primary mechanism for PCP removal in the HAIB was adsorption, effectively described by the Freundlich isotherm model. Adsorption efficiency ranged from 86 to 104% for PCP concentrations between 0.2 and 5.0 mg/L, and 46% to 64% for concentrations between 0.098 and 0.05 mg/L. Additionally, PCP degradation intermediates such as 2,3-DCP and 2,6-DCP were detected, indicating that biodegradation also occurred in the HAIB. Organic matter degradation averaged 81 ± 9%, and methane content in the biogas averaged 46 ± 9%, confirming the anaerobic process. No inhibition of microbial activity was observed due to PCP toxicity, even at a PCP load of 5 mg PCP/g STV per day. While the archaeal community showed only slight changes, with similarity coefficients ranging from 88 to 95%, the bacterial community was significantly affected by PCP, with similarity coefficients ranging from 18 to 50%. Bacterial groups were responsible for the initial PCP degradation, while the archaeal community was involved in metabolizing the resulting byproducts. The use of indigenous inoculum from the Santos-São Vicente estuary demonstrated its potential for effective PCP removal. Polyurethane foam proved to be an effective support material, enhancing the adsorption process and reducing PCP toxicity to the microbial consortium. This study provides valuable insights into PCP adsorption and biodegradation mechanisms in HAIB, highlighting the effectiveness of indigenous inoculum and polyurethane foam for PCP removal.

The metabolic activation of pentachlorophenol to chloranil as a potent inhibitor of human and rat placental 3ß-hydroxysteroid dehydrogenases.

Pentachlorophenol (PCP) is a widely used pesticide. However, whether PCP and its metabolite chloranil have endocrine-disrupting effects by inhibiting placental 3ß-hydroxysteroid dehydrogenase 1 (3ß-HSD1) remains unclear. The study used in vitro assays with human and rat placental microsomes to measure 3ß-HSD activity as well as human JAr cells to evaluate progesterone production. The results showed that PCP exhibited moderate inhibition of human 3ß-HSD1, with an IC50 value of 29.83 µM and displayed mixed inhibition in terms of mode of action. Conversely, chloranil proved to be a potent inhibitor, demonstrating an IC50 value of 147 nM, and displaying a mixed mode of action. PCP significantly decreased progesterone production by JAr cells at 50 µM, while chloranil markedly reduced progesterone production at ≥1 µM. Interestingly, PCP and chloranil moderately inhibited rat placental homolog 3ß-HSD4, with IC50 values of 27.94 and 23.42 µM, respectively. Dithiothreitol (DTT) alone significantly increased human 3ß-HSD1 activity. Chloranil not PCP mediated inhibition of human 3ß-HSD1 activity was completely reversed by DTT and that of rat 3ß-HSD4 was partially reversed by DTT. Docking analysis revealed that both PCP and chloranil can bind to the catalytic domain of 3ß-HSDs. The difference in the amino acid residue Cys83 in human 3ß-HSD1 may explain why chloranil is a potent inhibitor through its interaction with the cysteine residue of human 3ß-HSD1. In conclusion, PCP is metabolically activated to chloranil as a potent inhibitor of human 3ß-HSD1.

Co-exposure to pentachlorophenol (PCP) and cadmium (Cd) triggers apoptosis-like cell death in Eschericia coli.

Pentachlorophenol (PCP) - cadmium (Cd) complex pollution has been identified as a form of persistent soil pollution in south China, exerting detrimental impacts on the indigenous soil bacterial communities. Hence, it is worthwhile to investigate whether and how bacterial populations alter in response to these pollutants. In this study, Escherichia coli was used as a model bacterium. Results showed that PCP exposure caused bacterial cell membrane permeability changes, intracellular ROS elevation, and DNA fragmentation, and triggered apoptosis-like cell death at low exposure concentration and necrosis at high exposure concentration. Cd exposure caused severe oxidative damage and cell necrosis in the tested bacterial strain. The co-exposure to PCP and Cd elevated the ROS level, stimulated the bacterial caspase activity, and induced DNA fragmentation, thereby leading to an apoptosis-like cell death. In conclusion, PCP-Cd complex pollution can cause bacterial population to decrease through apoptosis-like cell death pathway. However, it is worth noting that the subpopulation survives under the complex pollution stress.

Effects of nano-TiO2 and pentachlorophenol on the bioenergetics of mussels under predatory stress.

Organic and nanoparticle pollutants are the main environmental problems affecting marine species, which have received great attention. However, the combined effect of pollutants on marine life in the presence of predators needs to be clarified. In this study, the effects of pentachlorophenol (PCP) and titanium dioxide nanoparticles (nano-TiO2) on the energy metabolism of mussels (Mytilus coruscus) in the presence of predators were assessed through cellular energy allocation (CEA) approach. Mussels were exposed to PCP (0, 1, and 10 µg/L), nano-TiO2 (1 mg/L, 25 and 100 nm), and predators (Portunus trituberculatus presence/absence) for 14 days. Exposure to high concentrations of PCP (10 µg/L) with small particle size nano-TiO2 (25 nm) decreased cellular energy stores (carbohydrates, lipids, and proteins) and increased cellular energy demand (measured as the activity of the mitochondrial electron transport system, ETS). During the first 7 days, energy was supplied mainly through the consumption of carbohydrates, while lipids are mobilized to participate after 7 days. The presence of predators caused a further decrease in energy stores. These findings demonstrate that PCP, nano-TiO2 and predators have a negative impact on energy metabolism at the cellular level. Carbohydrates are not able to meet the metabolic demand, lipids need to be consumed, and energy metabolism was also mediated by the involvement of proteins. Overall, our results suggest that PCP, nano-TiO2 and predators disrupt the cellular energy metabolism of mussels through reduced cellular energy allocation, small particles and predators drive mussels to exert energetic metabolic adjustments for detoxification reactions when toxic contaminants are present.

Toxicity assessment and detoxification metabolism of sodium pentachlorophenol (PCP-Na) on marine economic species: a case study of Moerella iridescens and Exopalaemon carinicauda.

Sodium pentachlorophenol (PCP-Na) is widespread in the marine environment; however, its impact on marine organisms remains under-researched. Moerella iridescens and Exopalaemon carinicauda are marine species of economic importance in China and under threat from PCP-Na pollution. Thus, this study aimed to assess the toxicity and detoxification metabolism of PCP-Na on M. iridescens and E. carinicauda. The study revealed that the 96 h median lethal concentration (LC50) of PCP-Na for M. iridescens and E. carinicauda were 9.895 mg/L and 14.143 mg/L, respectively. A species sensitivity distribution (SSD) for PCP-Na was developed specifically for marine organisms, determining a hazardous concentration to 5% of the species (HC5) of 0.047 mg/L. During the sub-chronic exposure period, PCP-Na accumulated significantly in M. iridescens and E. carinicauda, with highest concentrations of 41.22 mg/kg in the soft tissues of M. iridescens, 42.58 mg/kg in the hepatopancreas of E. carinicauda, and only 0.85 mg/kg in the muscle of E. carinicauda. Furthermore, the study demonstrated that detoxifying metabolic enzymes and antioxidant defense system enzymes of E. carinicauda responded stronger to PCP-Na compared to M. iridescens, suggesting that E. carinicauda may possess a stronger detoxification capacity. Notably, five biomarkers were identified and proposed for monitoring and evaluating PCP-Na contamination. Overall, the results indicated that M. iridescens and E. carinicauda exhibit greater tolerance to PCP-Na than other marine species, but they are susceptible to accumulating PCP-Na in their tissues, posing a significant health risk. Consequently, conducting aquatic health risk assessments in areas with potential PCP-Na contamination is strongly recommended.

Fungal Biotransformation of Hazardous Organic Compounds in Wood Waste.

A diverse spectrum of organisms, such as fungi, bacteria, and actinomycetes, can degrade and transform organic matter, including wood, into valuable nutrients. A sustainable economy has the goal of efficiently using waste as raw materials, and in this optic, it uses biological preparations more and more often, supporting the decomposition of lignocellulosic waste. With reference to wood wastes, which are produced in a substantial amount by the forest and wood industry, one of the possibilities to biodegrade such lignocellulosic material is the composting process. In particular, microbiological inoculum containing dedicated fungi can contribute to the biodegradation of wood waste, as well as the biotransformation of substances from the protection of wood, such as pentachlorophenol (PCP), lindane (hexachlorobenzene) and polycyclic aromatic hydrocarbons (PAHs). The purpose of this research was to produce a literature review in terms of the selection of decay fungi that could potentially be used in toxic biotransformation unions. The findings of the literature review highlighted how fungi such as Bjerkandera adusta, Phanerochaete chrysosporium, and Trametes versicolor might be ingredients of biological consortia that can be effectively applied in composting wood waste containing substances such as pentachlorophenol, lindane, and polycyclic aromatic hydrocarbons (PAHs).

Pentachlorophenol causes redox imbalance, inhibition of brush border membrane and metabolic enzymes, DNA damage and histological alterations in rat kidney.

Pentachlorophenol (PCP) is a synthetic organochlorine compound that is widely used in biocide and pesticide industries, and in preservation of wood, fence posts, cross arms and power line poles. Humans are usually exposed to PCP through air, contaminated water and food. PCP enters the body and adversely affects liver, gastrointestinal tract, kidney and lungs. PCP is a highly toxic class 2B or probable human carcinogen that produces large amount of reactive oxygen species (ROS) within cells. This work aimed to determine PCP-induced oxidative damage in rat kidney. Adult rats were given PCP (25, 50, 100, 150 mg/kg body weight), in corn oil, once a day for 5 days while control rats were given similar amount of corn oil by oral gavage. PCP increased hydrogen peroxide level and oxidation of thiols, proteins and lipids. The antioxidant status of kidney cells was compromised in PCP treated rats while enzymes of brush border membrane (BBM) and carbohydrate metabolism were inhibited. Plasma level of creatinine and urea was also increased. Administration of PCP increased DNA fragmentation, cross-linking of DNA to proteins and DNA strand scission in kidney. Histological studies supported biochemical findings and showed significant damage in the kidneys of PCP-treated rats. These changes could be due to redox imbalance or direct chemical modification by PCP or its metabolites. These results signify that PCP-induced oxidative stress causes nephrotoxicity, dysfunction of BBM enzymes and DNA damage.

Wide distribution of extracellular electron transfer functionality in natural proteinaceous organic materials for microbial reductive dehalogenation.

Extracellular electron transfer materials (EETMs) in the environment, such as humic substances and biochar, are formed from the humification/heating of natural organic materials. However, the distribution of extracellular electron transfer (EET) functionality in fresh natural organic materials has not yet been explored. In the present study, we reveal the wide distribution of EET functionality in proteinaceous materials for the first time using an anaerobic pentachlorophenol dechlorinating consortium, whose activity depends on EETM. Out of 11 natural organic materials and 13 reference compounds, seven proteinaceous organic materials (albumin, beef, milk, pork, soybean, yolk, and bovine serum albumin) functioned as EETMs. Carbohydrates and lipids did not function as EETMs. Comparative spectroscopic analyses suggested that a ß-sheet secondary structure was essential for proteins to function as EETMs, regardless of water solubility. A high content of reduced sulfur was potentially involved in EET functionality. Although proteinaceous materials have thus far been considered simply as nutrients, the wide distribution of EET functionality in these materials provides new insights into their impact on biogeochemical cycles. In addition, structural information on EET functionality can provide a scientific basis for the development of eco-friendly EETMs.

Complete pentachlorophenol biodegradation in a dual-working electrode bioelectrochemical system: Performance and functional microorganism identification.

Bioelectrochemical system (BES) can effectively promote the reductive dechlorination of chlorophenols (CPs). However, the complete degradation of CPs with sequential dechlorination and mineralization processes has rarely achieved from the BES. Here, a dual-working electrode BES was constructed and applied for the complete degradation of pentachlorophenol (PCP). Combined with DNA-stable isotope probing (DNA-SIP), the biofilms attached on the anodic and cathodic electrode in the BES were analyzed to explore the dechlorinating and mineralizing microorganisms. Results showed that PCP removal efficiency in the dual-working BES (84% for 21 days) was 4.1 and 4.7 times higher than those of conventional BESs with a single anodic or cathodic working electrode, respectively. Based on DNA-SIP and high-throughput sequencing analysis, the cathodic working electrode harbored the potential dechlorinators (Comamonas, Pseudomonas, Methylobacillus, and Dechlorosoma), and the anodic working enriched the potential intermediate mineralizing bacteria (Comamonas, Stenotrophomonas, and Geobacter), indicating that PCP could be completely degraded under the synergetic effect of these functional microorganisms. Besides, the potential autotrophic functional bacteria that might be involved in the PCP dechlorination were also identified by SIP labeled with 13C-NaHCO3. Our results proved that the dual-working BES could accelerate the complete degradation of PCP and enrich separately the functional microbial consortium for the PCP dechlorination and mineralization, which has broad potential for bioelectrochemical techniques in the treatment of wastewater contaminated with CPs or other halogenated organic compounds.

Study on the toxic effects of sodium pentachlorophenol (PCP-Na) on razor clam (Sinonovacula constricta).

Currently, research on toxic effects of PCP Na is greatly insufficient. The aim of this study is to explore the toxic effects of PCP-Na for better conducting future work on PCP-Na toxicology. For this purpose, S. constricta adults were exposed to PCP-Na for toxicity testing. The results showed that PCP-Na could easily bioaccumulate in S. constricta and significantly affected both phrase I and II metabolism enzymes. Meanwhile, PCP-Na strongly activated antioxidant system and caused PC, LPO and DNA damage. In addition, neurotoxicity and immunotoxicity of PCP-Na was demonstrated in this study. Interestingly, we observed that PCP-Na significantly affected the expression of genes of electron transport chain and induced key enzymes of glycolysis, indicating that PCP-Na may act as an uncoupler of oxidative phosphorylation, interfering with energy supply and causing energy compensation. This study is the first to fully analyze and provide a new perspective on the toxicity of PCP-Na.

Isolation and test of novel yeast strains with lignin usage capability and phenolic compound resistance.

Five yeast fungi strains (i.e., two Cryptococcus albidus, one Candida guillermondii, and two Candida tropicalis) were isolated from sugarcane and tested for their use of lignin as sole carbon source and their potential to grow in the presence of phenol and phenol derivatives (i.e., pentachlorophenol and p-nitrophenol). The full set of isolated yeasts showed ligninolytic activity, achieving at least 36% lignin degradation after 25 days. The C. albidus JS-B1 strain had the highest ligninolytic activity, achieving 27% lignin degradation within 4 days. This increased activity was associated with the production of ligninolytic laccase enzymes. All the tested yeast fungi strains showed growth in the presence of high concentrations of phenolic compounds (i.e., 900 mg/L phenol, 200 mg/L p-nitrophenol, 50 mg/L pentachlorophenol) and showed significant potential for lignin and lignin by-product degradation. Each of these five strains has the potential to be used in biological treatment processes for contaminated effluents from paper pulping and bleaching or phenol and phenol-derivative biodegradation processes for other industrial wastewater effluents.

Immunotoxicity of pentachlorophenol to a marine bivalve species and potential toxification mechanisms underpinning.

The ubiquitous presence of pentachlorophenol (PCP) in ocean environments threatens marine organisms. However, its effects on immunity of marine invertebrates at environmentally realistic levels are still largely unknown. In this study, the immunotoxicity of PCP to a representative bivalve species was evaluated. In addition, its impacts on metabolism, energy supply, detoxification, and oxidative stress status were also analysed by physiological examination as well as comparative transcriptomic and metabolomic analyses to reveal potential mechanisms underpinning. Results illustrated that the immunity of blood clams was evidently hampered upon PCP exposure. Additionally, significant alterations in energy metabolism were detected in PCP-exposed clams. Meanwhile, the expressions of key detoxification genes and the in vivo contents (or activity) of key detoxification enzymes were markedly altered. Exposure to PCP also triggered significant elevations in intracellular ROS and MDA whereas evident suppression of haemocyte viability. The abovementioned findings were further supported by transcriptomic and metabolomic analyses. Our results suggest that PCP may hamper the immunity of the blood clam by (i) constraining the cellular energy supply through disrupting metabolism; and (ii) damaging haemocytes through inducing oxidative stress. Considering the high similarity of immunity among species, many marine invertebrates may be threatened by PCP, which deserves more attention.

Concurrent anaerobic chromate bio-reduction and pentachlorophenol bio-degradation in a synthetic aquifer.

Chromate [Cr(VI)] and pentachlorophenol (PCP) coexist widely in the environment and are highly toxic to public health. However, whether Cr(VI) bio-reduction is accompanied by PCP bio-degradation and how microbial communities can keep long-term stability to mediate these bioprocesses in aquifer remain elusive. Herein, we conducted a 365-day continuous column experiment, during which the concurrent removals of Cr(VI) and PCP were realized under anaerobic condition. This process allowed for complete Cr(VI) bio-reduction and PCP bio-degradation at an efficiency of 92.8 ± 4.2% using ethanol as a co-metabolic substrate. More specifically, Cr(VI) was reduced to insoluble chromium (III) and PCP was efficiently dechlorinated with chloride ion release. Collectively, Acinetobacter and Spirochaeta regulated Cr(VI) bio-reduction heterotrophically, while Pseudomonas mediated not only Cr(VI) bio-reduction but also PCP bio-dechlorination. The bio-dechlorinated products were further mineralized by Azospira and Longilinea. Genes encoding proteins for Cr(VI) bio-reduction (chrA and yieF) and PCP bio-degradation (pceA) were upregulated. Cytochrome c and intracellular nicotinamide adenine dinucleotide were involved in Cr(VI) and PCP detoxification by promoting electron transfer. Taken together, our findings provide a promising bioremediation strategy for concurrent removal of Cr(VI) and PCP in aquifers through bio-stimulation with supplementation of appropriate substrates.

3,4-Dihydroxybenzaldehyde attenuates pentachlorophenol-induced cytotoxicity, DNA damage and collapse of mitochondrial membrane potential in isolated human blood cells.

Pentachlorophenol (PCP) is a chlorophenolic compound that is widely used as pesticide, biocide and as a wood preservative to treat utility poles and wharf pilings. PCP is rapidly absorbed through the gastrointestinal tract and enters the blood where it generates active oxygen species in target cells. We have, therefore, examined the protective effect of plant antioxidant 3,4-dihydroxybenzaldehyde (DHB) against PCP-induced cyto-and geno-toxicity in human red blood cells (RBC) and lymphocytes, respectively. Human RBC were incubated at 37°C with 0.75 mM PCP, either alone or in presence of different concentrations of DHB (0.05-2.0 mM). Several biochemical parameters were determined in whole cells and hemolysates. Incubation of RBC with PCP alone increased the formation of reactive oxygen and nitrogen species (ROS and RNS) that resulted in oxidation of proteins, lipids, cellular thiols and plasma membrane damage. The antioxidant defense system was impaired and glucose metabolism was inhibited. However, prior treatment of RBC with DHB lowered ROS and RNS generation and attenuated PCP-induced oxidative damage of cell components. DHB alone enhanced electron transport by the plasma membrane redox system and also prevented its inhibition by PCP. DHB significantly prevented PCP-induced transformation of RBC morphology from normal biconcave shape to spherocytes, spiculated acanthocytes and echinocytes. DHB protected human lymphocytes from PCP-induced DNA damage and strand breaks, lysosomal membrane damage and collapse of the mitochondrial membrane potential. These results show that DHB mitigates PCP-induced cytotoxicity and can potentially function as a chemoprotective agent against the harmful effects of PCP and possibly other chlorophenols.

Exhaustion of pentachlorophenol in soil microcosms with three Pseudomonas species as detoxification agents.

Pentachlorophenol (PCP) is a toxic compound, which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Bioremediation is an emerging approach to rehabilitating areas polluted by recalcitrant xenobiotics. In the present study, we evaluated the potential of three strains of Pseudomonas (P. putida S121, P. rhizophila S211, and P. fuscovagiceae S115) as bioremediation agents in depletion and detoxification of PCP in soil microcosms. PCP removal was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum PCP removal yield (85 ± 5%) were: 500 mg/kg PCP concentration, 108 UFC/g soil inoculum size of each strain and 55 days incubation period. The bacterial strains, P. putida, P. rhizophila, and P. fuscovagiceae, showed good capability to tolerate and degrade PCP so that they could be successfully used in synergistic effect to treat PCP polluted soils.

Whole-genome sequencing, genome mining, metabolic reconstruction and evolution of pentachlorophenol and other xenobiotic degradation pathways in Bacillus tropicus strain AOA-CPS1.

A pentachlorophenol degrading bacterium was isolated from effluent of a wastewater treatment plant in Durban, South Africa, and identified as Bacillus tropicus strain AOA-CPS1 (BtAOA). The isolate degraded 29% of pentachlorophenol (PCP) within 9 days at an initial PCP concentration of 100 mg L-1 and 62% of PCP when the initial concentration was set at 350 mg L-1. The whole-genome of BtAOA was sequenced using Pacific Biosciences RS II sequencer with the Single Molecule, Real-Time (SMRT) Link (version 7.0.1.66975) and analysed using the HGAP4-de-novo assembly application. The contigs were annotated at NCBI, RASTtk and PROKKA prokaryotic genome annotation pipelines. The BtAOA genome is comprised of a 5,246,860-bp chromosome and a 58,449-bp plasmid with a GC content of 35.4%. The metabolic reconstruction for BtAOA showed that the organism has been naturally exposed to various chlorophenolic compounds including PCP and other xenobiotics. The chromosome encodes genes for core processes, stress response and PCP catabolic genes. Analogues of PCP catabolic gene (cpsBDCAE, and p450) sequences were identified from the NCBI annotation data, PCR-amplified from the whole genome of BtAOA, cloned into pET15b expression vector, overexpressed in E. coli BL21 (DE3) expression host, purified and characterized. Sequence mining and comparative analysis of the metabolic reconstruction of the BtAOA genome with closely related strains suggests that the operon encoding the first two enzymes in the PCP degradation pathway were acquired from a pre-existing pterin-carbinolamine dehydratase subsystem. The other two enzymes were recruited via horizontal gene transfer (HGT) from the pool of hypothetical proteins with no previous specific function, while the last enzyme was recruited from pre-existing enzymes from the TCA or serine-glyoxalase cycle via HGT events. This study provides a comprehensive understanding of the role of BtAOA in PCP degradation and its potential exploitation for bioremediation of other xenobiotic compounds.

Pentachlorophenol inhibits CatSper function to compromise progesterone's action on human sperm.

Pentachlorophenol (PCP), a highly toxic contaminant of chlorophenols, is common in a variety of environments and presents serious risks to animal and human health. However, the reproductive toxicity and potential actions of PCP have not been investigated thoroughly, especially in humans. Here, human spermatozoa were used to evaluate the effect of PCP on cell function and to explore the underlying mechanisms. PCP had no substantive effects on sperm viability or motility, nor on the ability to penetrate viscous medium, sperm hyperactivation or spontaneous acrosome reactions. However, PCP significantly inhibited these properties induced by progesterone (P4). Consistent with the functional observations, although PCP itself did not affect the basal intracellular Ca2+ concentrations and CatSper current, PCP dose-dependently inhibited increases of intracellular Ca2+ concentrations caused by P4. In addition, the activation of CatSper induced by P4 was largely suppressed by PCP. This is the first report showing that PCP may serves as an antagonist of the P4 membrane receptor to interfere with Ca2+ signaling by compromising the action of P4 on regulating sperm function. These findings suggest that the reproductive toxicity of PCP should also be a matter of concern as a mammalian health risk.

Role of tetrachloro-1,4-benzoquinone reductase in phenylalanine hydroxylation system and pentachlorophenol degradation in Bacillus cereus AOA-CPS1.

This study reports a ≅12.5 kDa protein tetrachloro-1,4-benzoquinone reductase (CpsD) from Bacillus cereus strain AOA-CPS1 (BcAOA). CpsD is purified to homogeneity with a total yield of 35% and specific activity of 160 U·mg-1 of protein. CpsD showed optimal activity at pH 7.5 and 40 °C. The enzyme was found to be functionally stable between pH 7.0-7.5 and temperature between 30 °C and 35 °C. CpsD activity was enhanced by Fe2+ and inhibited by sodium azide and SDS. CpsD followed Michaelis-Menten kinetic exhibiting an apparent vmax, Km, kcat and kcat/Km values of 0.071 µmol·s-1, 94 µmol, 0.029 s-1 and 3.13 × 10-4 s-1·µmol-1, respectively, for substrate tetrachloro-1,4-benzoquinone. The bioinformatics analysis indicated that CpsD belongs to the PCD/DCoH superfamily, with specific conserved protein domains of pterin-4α-carbinolamine  dehydratase (PCD). This study proposed that CpsD catalysed the reduction of tetrachloro-1,4-benzoquinone to tetrachloro-p-hydroquinone and released the products found in phenylalanine hydroxylation system (PheOHS) via a Ping-Pong or atypical ternary mechanism; and regulate expression of phenylalanine 4-monooxygenase by blocking reverse flux in BcAOA PheOHS using a probable Yin-Yang mechanism. The study also concluded that CpsD may play a catalytic and regulatory role in BcAOA PheOHS and pentachlorophenol degradation pathway.

Functional analysis of novel sulfotransferases in the silkworm Bombyx mori.

Sulfoconjugation plays a vital role in the detoxification of xenobiotics and in the metabolism of endogenous compounds. In this study, we aimed to identify new members of the sulfotransferase (SULT) superfamily in the silkworm Bombyx mori. Based on amino acid sequence and phylogenetic analyses, two new enzymes, swSULT ST1 and swSULT ST2, were identified that appear to belong to a distinct group of SULTs including several other insect SULTs. We expressed, purified, and characterized recombinant SULTs. While swSULT ST1 sulfated xanthurenic acid and pentachlorophenol, swSULT ST2 exclusively utilized xanthurenic acid as a substrate. Based on these results, and those concerning the tissue distribution and substrate specificity toward pentachlorophenol analyses, we hypothesize that swSULT ST1 plays a role in the detoxification of xenobiotics, including insecticides, in the silkworm midgut and in the induction of gametogenesis in silkworm ovary and testis. Collectively, the data obtained herein contribute to a better understanding of SULT enzymatic functions in insects.

Titanium dioxide nanoparticles enhanced thyroid endocrine disruption of pentachlorophenol rather than neurobehavioral defects in zebrafish larvae.

This study investigated the influences of titanium dioxide nanoparticles (n-TiO2) on the thyroid endocrine disruption and neurobehavioral defects induced by pentachlorophenol (PCP) in zebrafish (Danio rerio). Embryos (2 h post-fertilization) were exposed to PCP (0, 3, 10, and 30 µg/L) or in combination with n-TiO2 (0.1 mg/L) until 6 days post-fertilization. The results showed that n-TiO2 alone did not affect thyroid hormones levels or transcriptions of related genes. Exposure to PCP significantly decreased thyroid hormone thyroxine (T4) content, thyroid stimulating hormone (TSH) level and transcription of thyroglobulin (tg), but significantly increased 3,5,3'-triiodothyronine (T3) level and upregulation of deiodinase 2 (dio2). In comparison, the co-exposure with n-TiO2 significantly reduced the content of T3 by depressing the potential targets, tg and dio2. For neurotoxicity, the single and co-exposure resulted in similar effects with significant downregulation of neurodevelopment-related genes (ELAV like RNA Binding Protein 3, elavl3; Growth associated protein-43, gap43; α-tubulin) and inhibited locomotor activity. The results indicated that the presence of n-TiO2 significantly enhanced the PCP-induced thyroid endocrine disruption but not the neurobehavioral defects in zebrafish larvae.