L-amino acid oxidase from snake venom: Biotransformation and induction of apoptosis in human colon cancer cells.

This study evaluated the potential of antitumor activity of snake venom from Vipera ammodytes and L-amino acid oxidase from Crotalus adamanteus on different colorectal cancer cell lines through determination of cytotoxic activity by MTT assay, pro-apoptotic activity by acridine orange/ethidium bromide staining, and concentrations of redox status parameters (superoxide, reduced glutathione, lipid peroxidation) by colorimetric methods. The expression of genes involved in the biotransformation process and metabolite efflux was determined by qPCR method, while protein expression of glutathione synthetase and P-glycoprotein were analysed by immunocytochemistry. The analysis of cell death shows that snake venom dominantly leads cells to necrosis. Induction of apoptosis by L-amino acid oxidase was in correlation with oxidative disbalance in cancer cells. Gene expression profile of membrane transporters and CYP genes were different in each cell line and in correlation with their sensitivity of treatment. Our results show that L-amino acid oxidase from snake venom is a potent cytotoxic substance with pronounced pro-apoptotic activity. The inhibition of P-glycoprotein suggests that L-amino acid oxidase is a good substance for furter research of antitumor effect, with unexpressed potential for occurrence of drug resistance in vitro.

Novel Cold-Adapted Recombinant Laccase KbLcc1 from Kabatiella bupleuri G3 IBMiP as a Green Catalyst in Biotransformation.

Cold-adapted enzymes are useful tools in the organic syntheses conducted in mixed aqueous-organic or non-aqueous solvents due to their molecular flexibility that stabilizes the proteins in low water activity environments. A novel psychrophilic laccase gene from Kabatiella bupleuri, G3 IBMiP, was spliced by Overlap-Extension PCR (OE-PCR) and expressed in Pichia pastoris. Purified recombinant KbLcc1 laccase has an optimal temperature of 30 °C and pH of 3.5, 5.5, 6.0, and 7.0 in the reaction with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), guaiacol, sinapic acid, and syringaldazine, respectively. Moreover, laccase KbLcc1 is highly thermolabile, as it loses 40% of activity after 30 min at 40 °C and is inactivated at 50 °C after the same period of incubation. The new enzyme remained active with 1 mM of Ni2+, Cu2+, Mn2+, and Zn2+ and with 2 mM of Co2+, Ca2+, and Mg2+, but Fe2+ greatly inhibited the laccase activity. Moreover, 1% ethanol had no impact on KbLcc1, although acetone and ethyl acetate decreased the laccase activity. The presence of hexane (40%, v/v) caused a 58% increase in activity. Laccase KbLcc1 could be applied in the decolorization of synthetic dyes and in the biotransformation of ferulic acid to vanillin. After 5 days of reaction at 20 °C, pH 3.5, with 1 mM ABTS as a mediator, the vanillin concentration was 21.9 mg/L and the molar yield of transformation reached 14.39%.

Pregnane X Receptor (PXR) Polymorphisms and Cancer Treatment.

Pregnane X Receptor (PXR) belongs to the nuclear receptors' superfamily and mainly functions as a xenobiotic sensor activated by a variety of ligands. PXR is widely expressed in normal and malignant tissues. Drug metabolizing enzymes and transporters are also under PXR's regulation. Antineoplastic agents are of particular interest since cancer patients are characterized by significant intra-variability to treatment response and severe toxicities. Various PXR polymorphisms may alter the function of the protein and are linked with significant effects on the pharmacokinetics of chemotherapeutic agents and clinical outcome variability. The purpose of this review is to summarize the roles of PXR polymorphisms in the metabolism and pharmacokinetics of chemotherapeutic drugs. It is also expected that this review will highlight the importance of PXR polymorphisms in selection of chemotherapy, prediction of adverse effects and personalized medicine.

The Aryl hydrocarbon receptor mediates reproductive toxicity of polychlorinated biphenyl congener 126 in rats.

Polychlorinated biphenyls (PCBs) are endocrine disrupting chemicals with documented, though mechanistically ill-defined, reproductive toxicity. The toxicity of dioxin-like PCBs, such as PCB126, is mediated via the aryl hydrocarbon receptor (AHR) in non-ovarian tissues. The goal of this study was to examine the uterine and ovarian effects of PCB126 and test the hypothesis that the AHR is required for PCB126-induced reproductive toxicity. Female Holzman-Sprague Dawley wild type (n = 14; WT) and Ahr knock out (n = 11; AHR-/-) rats received a single intraperitoneal injection of either corn oil vehicle (5 ml/kg: WT_O and AHR-/-_O) or PCB126 (1.63 mg/kg in corn oil: WT_PCB and AHR-/-_PCB) at four weeks of age. The estrous cycle was synchronized and ovary and uterus were collected 28 days after exposure. In WT rats, PCB126 exposure reduced (P < 0.05) body and ovary weight, uterine gland number, uterine area, progesterone, 17ß-estradiol and anti-Müllerian hormone level, secondary and antral follicle and corpora lutea number but follicle stimulating hormone level increased (P < 0.05). In AHR-/- rats, PCB126 exposure increased (P ≤ 0.05) circulating luteinizing hormone level. Ovarian or uterine mRNA abundance of biotransformation, and inflammation genes were altered (P < 0.05) in WT rats due to PCB126 exposure. In AHR-/- rats, the transcriptional effects of PCB126 were restricted to reductions (P < 0.05) in three inflammatory genes. These findings support a functional role for AHR in the female reproductive tract, illustrate AHR's requirement in PCB126-induced reprotoxicity, and highlight the potential risk of dioxin-like compounds on female reproduction.

The why behind the high: determinants of neurocognition during acute cannabis exposure.

Acute cannabis intoxication may induce neurocognitive impairment and is a possible cause of human error, injury and psychological distress. One of the major concerns raised about increasing cannabis legalization and the therapeutic use of cannabis is that it will increase cannabis-related harm. However, the impairing effect of cannabis during intoxication varies among individuals and may not occur in all users. There is evidence that the neurocognitive response to acute cannabis exposure is driven by changes in the activity of the mesocorticolimbic and salience networks, can be exacerbated or mitigated by biological and pharmacological factors, varies with product formulations and frequency of use and can differ between recreational and therapeutic use. It is argued that these determinants of the cannabis-induced neurocognitive state should be taken into account when defining and evaluating levels of cannabis impairment in the legal arena, when prescribing cannabis in therapeutic settings and when informing society about the safe and responsible use of cannabis.

Genetic ancestry plays a central role in population pharmacogenomics.

Recent studies have pointed out the essential role of genetic ancestry in population pharmacogenetics. In this study, we analyzed the whole-genome sequencing data from The 1000 Genomes Project (Phase 3) and the pharmacogenetic information from Drug Bank, PharmGKB, PharmaADME, and Biotransformation. Here we show that ancestry-informative markers are enriched in pharmacogenetic loci, suggesting that trans-ancestry differentiation must be carefully considered in population pharmacogenetics studies. Ancestry-informative pharmacogenetic loci are located in both protein-coding and non-protein-coding regions, illustrating that a whole-genome analysis is necessary for an unbiased examination over pharmacogenetic loci. Finally, those ancestry-informative pharmacogenetic loci that target multiple drugs are often a functional variant, which reflects their importance in biological functions and pathways. In summary, we develop an efficient algorithm for an ultrahigh-dimensional principal component analysis. We create genetic catalogs of ancestry-informative markers and genes. We explore pharmacogenetic patterns and establish a high-accuracy prediction panel of genetic ancestry. Moreover, we construct a genetic ancestry pharmacogenomic database Genetic Ancestry PhD ( http://hcyang.stat.sinica.edu.tw/databases/genetic_ancestry_phd/ ).

Integrated gene engineering synergistically improved substrate-product transport, cofactor generation and gene translation for cadaverine biosynthesis in E. coli.

Several approaches for efficient production of cadaverine, a bio-based diamine with broad industrial applications have been explored. Here, Serratia marcescens lysine decarboxylase (SmcadA) was expressed in E. coli; mild surfactants added in biotransformation reactions; the E. coli native lysine/cadaverine antiporter cadB, E. coli pyridoxal kinases pdxK and pdxY overexpressed and synthetic RBS libraries screened. Addition of mild surfactants and overexpression of antiporter cadB increased cadaverine biosynthesis of SmcadA. Moreover, expression of pdxY gene yielded 19.82 g/L in a reaction mixture containing added cofactor precursor pyridoxal (PL), without adding exogenous PLP. The screened synthetic RBS1, applied to fully exploit pdxY gene expression, ultimately resulted in PLP self-sufficiency, producing 27.02 g/L cadaverine using strain T7R1_PL. To boost SmcadA catalytic activity, the designed mutants Arg595Lys and Ser512Ala had significantly improved cumulative cadaverine production of 219.54 and 201.79 g/L respectively compared to the wild-type WT (181.62 g/L), after 20 h reaction. Finally, molecular dynamics simulations for WT and variants indicated that increased flexibility at the binding sites of the protein enhanced residue-ligand interactions, contributing to high cadaverine synthesis. This work demonstrates potential of harnessing different pull factors through integrated gene engineering of efficient biocatalysts and gaining insight into the mechanisms involved through MD simulations.

Distinct Effects of Inflammation on Cytochrome P450 Regulation and Drug Metabolism: Lessons from Experimental Models and a Potential Role for Pharmacogenetics.

Personalized medicine strives to optimize drug treatment for the individual patient by taking into account both genetic and non-genetic factors for drug response. Inflammation is one of the non-genetic factors that has been shown to greatly affect the metabolism of drugs-primarily through inhibition of cytochrome P450 (CYP450) drug-metabolizing enzymes-and hence contribute to the mismatch between the genotype predicted drug response and the actual phenotype, a phenomenon called phenoconversion. This review focuses on inflammation-induced drug metabolism alterations. In particular, we discuss the evidence assembled through human in-vitro models on the effect of inflammatory mediators on clinically relevant CYP450 isoform levels and their metabolizing capacity. We also present an overview of the current understanding of the mechanistic pathways via which inflammation in hepatocytes may modulate hepatic functions that are critical for drug metabolism. Furthermore, since large inter-individual variability in response to inflammation is observed in human in-vitro models and clinical studies, we evaluate the potential role of pharmacogenetic variability in the inflammatory signaling cascade and how this can modulate the outcome of inflammation on drug metabolism and response.

Identification of the Gene Responsible for Lignin-Derived Low-Molecular-Weight Compound Catabolism in Pseudomonas sp. Strain LLC-1.

Pseudomonas sp. strain LLC-1 (NBRC 111237) is capable of degrading lignin-derived low-molecular-weight compounds (LLCs). The genes responsible for the catabolism of LLCs were characterized in this study using whole-genome sequencing. Despite the close phylogenetic relationship with Pseudomonas putida, strain LLC-1 lacked the genes usually found in the P. putida genome, which included fer, encoding an enzyme for ferulic acid catabolism, and vdh encoding an NAD+-dependent aldehyde dehydrogenase specific for its catabolic intermediate, vanillin. Cloning and expression of the 8.5 kb locus adjacent to the van operon involved in vanillic acid catabolism revealed the bzf gene cluster, which is involved in benzoylformic acid catabolism. One of the structural genes identified, bzfC, expresses the enzyme (BzfC) having the ability to transform vanillin and syringaldehyde to corresponding acids, indicating that BzfC is a multifunctional enzyme that initiates oxidization of LLCs in strain LLC-1. Benzoylformic acid is a catabolic intermediate of (R,S)-mandelic acid in P. putida. Strain LLC-1 did not possess the genes for mandelic acid racemization and oxidation, suggesting that the function of benzoylformic acid catabolic enzymes is different from that in P. putida. Genome-wide characterization identified the bzf gene responsible for benzoylformate and vanillin catabolism in strain LLC-1, exhibiting a unique mode of dissimilation for biomass-derived aromatic compounds by this strain.

Diclofenac Degradation-Enzymes, Genetic Background and Cellular Alterations Triggered in Diclofenac-Metabolizing Strain Pseudomonas moorei KB4.

Diclofenac (DCF) constitutes one of the most significant ecopollutants detected in various environmental matrices. Biological clean-up technologies that rely on xenobiotics-degrading microorganisms are considered as a valuable alternative for chemical oxidation methods. Up to now, the knowledge about DCF multi-level influence on bacterial cells is fragmentary. In this study, we evaluate the degradation potential and impact of DCF on Pseudomonas moorei KB4 strain. In mono-substrate culture KB4 metabolized 0.5 mg L-1 of DCF, but supplementation with glucose (Glc) and sodium acetate (SA) increased degraded doses up to 1 mg L-1 within 12 days. For all established conditions, 4'-OH-DCF and DCF-lactam were identified. Gene expression analysis revealed the up-regulation of selected genes encoding biotransformation enzymes in the presence of DCF, in both mono-substrate and co-metabolic conditions. The multifactorial analysis of KB4 cell exposure to DCF showed a decrease in the zeta-potential with a simultaneous increase in the cell wall hydrophobicity. Magnified membrane permeability was coupled with the significant increase in the branched (19:0 anteiso) and cyclopropane (17:0 cyclo) fatty acid accompanied with reduced amounts of unsaturated ones. DCF injures the cells which is expressed by raised activities of acid and alkaline phosphatases as well as formation of lipids peroxidation products (LPX). The elevated activity of superoxide dismutase (SOD) and catalase (CAT) testified that DCF induced oxidative stress.

Cloning and heterologous expression of P450Lent4B11, a novel bacterial P450 gene, for hydroxylation of an antifungal agent sordaricin.

Microbial transformation is known to be one of promising options to add functional groups such as a hydroxyl moiety to active base compounds to generate their derivatives. Sordaricin, a diterpene aglycone of the natural product sordarin, is an antifungal agent to selectively inhibit fungal protein synthesis by stabilizing the ribosome/EF-2 (elongation factor 2) complex. We screened actinomycetes to catalyze hydroxylation of sordaricin on the basis that the hydroxyl moiety would make it easier to generate derivatives of sordaricin. As a result of the screening, 6-hydroxylation of sordaricin was found to be catalyzed by Lentzea sp. 7887. We found that the cytochrome P450 inhibitor metyrapone inhibited this reaction, suggesting that a cytochrome P450 may be responsible for the biotransformation. As a next step, we cloned multiple cytochrome P450 genes, one of which were named P450Lent4B11, using degenerate PCR primers. The expressed cytochrome P450 derived from the P450Lent4B11 gene provided a different absorbance spectrum pattern from original one when it was incubated with sordaricin. Moreover, in cell-free conditions, the corresponding cytochrome P450 displayed the 6-hydroxylation activity toward sordaricin. Taken together, these results indicate that P450Lent4B11, derived from Lentzea sp. 7887, should be responsible for catalyzing 6-hydroxylation of sordaricin.

Effects of 27 natural products on drug metabolism genes in channel catfish (Ictalurus punctatus) cell line.

Pregnane X receptor (PXR) as a ligand dependent transcription factor, is capable of regulating gene expression of cytochromes P450 and transporters involved in xenobiotic/drug metabolism and elimination. Due to the species differences in the regulatory specificity of PXR, gene regulation should not be extrapolated from mammal to fish without research data.The aim of present study was to investigate the effect of 27 natural products on PXR, CYP3A30 and MDR1 genes in channel catfish (Ietalurus punetaus) kidney cells (CC-K). The results showed that bisdemethoxycurcumin, glycyrrhetnic acid, rotenone, artemisinin, dihydroartemisinin, ligustilide and matrine strongly induced the mRNA levels of PXR. Additionally, the up-regulation of CYP3A30 gene ran parallel with PXR gene after the treatment of demethoxycurcumin, glycyrrhetnic acid, artemisinin, matrine, baicalein, schisantherin A, ligustilide, and dihydroartemisinin. Moreover, we found that natural products schisandrin A, schisandrin B, schisandrol A, and schisandrol B significantly up-regulated the mRNA level of MDR1 gene.Our work with a view to provide experimental data support for further research, which will make for the rational application of natural products in channel catfish, such as to avoid adverse herb-drug interactions or accelerating the residue elimination of chemical medicine.

The role of candidate genetic polymorphisms in the interaction between voriconazole and cyclosporine in patients undergoing allogeneic hematopoietic cell transplantation: An explorative study.

PURPOSE: To evaluate polymorphisms in genes of drug metabolizing enzymes and transporters involved in cyclosporine and/or voriconazole disposition among patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). METHODS: DNA from forty patients was genotyped using the DMETPlus array. The average ratio of cyclosporine concentration/dose (C/D in (ng/mL)/(mg/kg)) per participant's weight was computed using available trough levels and daily doses. RESULTS: The C/D cyclosporine ratio was significantly higher when it was administered with voriconazole as compared to when it was administered alone: median: 116.75 vs. 25.40 (ng/mL)/(mg/kg) with and without voriconazole respectively, (P < 0.001). There was also a significant association between the C/D cyclosporine ratio combined with voriconazole and the ABCB1 2677 G > T > A (rs2032582) genetic polymorphism (P = 0.05). In parallel, ABCB1 variant allele carriers had higher creatinine in combination therapy with a median creatinine (mg/dL) of 0.74 vs. 0.56 for variant allele carriers vs. reference; P = 0.003. Interestingly, CYP2C9, CYP2C19, and CYP3A5 extensive metabolizers tended to be associated with lower cyclosporine C/D ratio when combined with voriconazole, but the results were not statistically significant. CONCLUSION: To the best of our knowledge, this is the first pharmacogenetic study on the interaction between voriconazole and cyclosporine in patients undergoing allo-HCT. Results suggest that the ABCB1 2677 G > T > A genetic polymorphism plays a role in this interaction with cyclosporine related nephrotoxicity. Pre-emptive genotyping for this genetic variant may be warranted for cyclosporine dose optimization. Larger studies are needed to potentially show significant associations with more candidate genes such as CYP3A4/5, CYP2C9, and CYP2C19, among others.

The characterization of arsenic biotransformation microbes in paddy soil after straw biochar and straw amendments.

Straw biochar and straw application to paddy soil dramatically altered arsenic (As) biogeochemical cycling in soil-rice system, but it remains unknown how As biotransformation microbes (ABMs) contribute to these processes. In this study, rice pot experiments combining terminal restriction fragment length polymorphism (T-RFLP) analysis and clone library were performed to characterize ABMs. Through linear discriminant analysis (LDA) effect size (LEfSe) and correlation analysis, results revealed that arrA-harbouring iron-reducing bacteria (e.g., Geobacter and Shewanella) and arsC-harbouring Gammaproteobacteria (e.g., fermentative hydrogen-producing and lignin-degrading microorganisms) potentially mediated arsenate [As(V)] reduction under biochar and straw amendments, respectively. Methanogens and sulfate-reducing bacteria (SRB) carrying arsM gene might regulate methylated As concentration in soil-rice system. Network analysis demonstrated that the association among ABMs in rhizosphere was significantly stronger than that in bulk soil. Arsenite [As(III)] methylators carrying arsM gene exhibited much stronger co-occurrence pattern with arsC-harbouring As(V) reducers than with arrA-harbouring As(V) reducers. This study would broaden our insights for the dramatic variation of As biogeochemical cycling in soil-rice system after straw biochar and straw amendments through the activities of ABMs, which could contribute to the safe rice production and high rice yield in As-contaminated fields.

Genetic studies of urinary metabolites illuminate mechanisms of detoxification and excretion in humans.

The kidneys integrate information from continuous systemic processes related to the absorption, distribution, metabolism and excretion (ADME) of metabolites. To identify underlying molecular mechanisms, we performed genome-wide association studies of the urinary concentrations of 1,172 metabolites among 1,627 patients with reduced kidney function. The 240 unique metabolite-locus associations (metabolite quantitative trait loci, mQTLs) that were identified and replicated highlight novel candidate substrates for transport proteins. The identified genes are enriched in ADME-relevant tissues and cell types, and they reveal novel candidates for biotransformation and detoxification reactions. Fine mapping of mQTLs and integration with single-cell gene expression permitted the prioritization of causal genes, functional variants and target cell types. The combination of mQTLs with genetic and health information from 450,000 UK Biobank participants illuminated metabolic mediators, and hence, novel urinary biomarkers of disease risk. This comprehensive resource of genetic targets and their substrates is informative for ADME processes in humans and is relevant to basic science, clinical medicine and pharmaceutical research.

Enhancement in catalytic activity of CotA-laccase from Bacillus pumilus W3 via site-directed mutagenesis.

CotA-laccases are potential enzymes that are widely used in decolorization of dyes and degradation of toxic substances. In this study, a novel CotA-laccase gene from Bacillus pumilus W3 was applied for rational design. After a series of site-directed genetic mutations, the mutant S208G/F227A showed a 5.1-fold higher catalytic efficiency (kcat/Km) than the wild-type CotA-laccase did. The optimal pH of S208G/F227A was 3.5 with ABTS as substrate. The residual activity of mutant S208G/F227A was more than 80% after incubated for 10 h at pH 7-11. Mutant S208G/F227A showed optimal temperature at 80°C with ABTS as substrate. The thermal stability of mutant laccase S208G/F227A was lower than that of wild-type CotA-laccase. This study showed that Gly208 and Ala227 play key roles in catalytic efficiency and it is possible to improve catalytic efficiency of CotA-laccase through site-directed mutagenesis.

Unexpected intracellular biodegradation and recrystallization of gold nanoparticles.

Gold nanoparticles are used in an expanding spectrum of biomedical applications. However, little is known about their long-term fate in the organism as it is generally admitted that the inertness of gold nanoparticles prevents their biodegradation. In this work, the biotransformations of gold nanoparticles captured by primary fibroblasts were monitored during up to 6 mo. The combination of electron microscopy imaging and transcriptomics study reveals an unexpected 2-step process of biotransformation. First, there is the degradation of gold nanoparticles, with faster disappearance of the smallest size. This degradation is mediated by NADPH oxidase that produces highly oxidizing reactive oxygen species in the lysosome combined with a cell-protective expression of the nuclear factor, erythroid 2. Second, a gold recrystallization process generates biomineralized nanostructures consisting of 2.5-nm crystalline particles self-assembled into nanoleaves. Metallothioneins are strongly suspected to participate in buildings blocks biomineralization that self-assembles in a process that could be affected by a chelating agent. These degradation products are similar to aurosomes structures revealed 50 y ago in vivo after gold salt therapy. Overall, we bring to light steps in the lifecycle of gold nanoparticles in which cellular pathways are partially shared with ionic gold, revealing a common gold metabolism.

Gene Polymorphism of Xenobiotic Biotransformation Enzymes in Patients with Classical Ph-Negative Myeloproliferative Neoplasms.

The correlation of gene polymorphisms rs4025935 (large deletion), rs1695 (313A>G), rs71748309 (large deletion), and rs1800566 (609C>T) of GSTM1, GSTT1, and NQO1 genes encoding glutathione-S-transferases (GST) M1, P1, and T1 and NADPH-quinone oxidoreductase with the risk of development of classical Ph-negative myeloproliferative neoplasms (polycythemia vera, essential thrombocythemia, and primary myelofibrosis) was studied in the Caucasian ethnicity population of Vyatka region of the Russian Federation. It was found that NQO1*609T allele, NQO1*609T genotypes, and homozygous carriage of a deletion (null) allele of GSTT1 gene are associated with the risk of development of myeloproliferative neoplasms (OR=1.29, 95%CI=1.02-1.64, p=0.04; OR=1.39, 95%CI=1.04-1.85, p=0.03; and OR=1.48, 95%CI=1.03-2.12, p=0.03, respectively). However, no influence of GSTM1 and GSTP1 gene polymorphisms on the risk of development of myeloproliferative disorders was registered.

Distribution of arsenic and its biotransformation genes in sediments from the East China Sea.

Microbial transformation of arsenic (As) plays a key role in As biogeochemical cycling and affects the mobility, bioavailability, and toxicity of As. This study aims to investigate the accumulation of As in marine sediments at different water depths in the East China Sea and reveal the abundance and diversity of the aioA, arrA, arsC, and arsM genes through quantitative real-time polymerase chain reaction (qPCR) and high-throughput sequencing. Results showed that the As content in sediments ranged from 5.53 mg kg-1 to 17.70 mg kg-1, which decreased with water depth. Abundant As biotransformation genes with low diversity were identified in these sediments, of which arsM and arrA were the most abundant. Significant positive correlation exists between the arsM and arrA gene abundance and between arsC and aioA, indicating the co-occurrence of the As biotransformation genes in microbes in marine sediments. Metagenomics analysis revealed that arsM gene was mainly distributed in Alphaproteobacteria, Solibacteres, Deltaproteobacteria, Clostridia, and Bacilli in these sediments. Among the sediment properties, total N, total S, C/N, and TOC were important factors that shaped the abundance profile of the genes involved in As transformation. This study provides a picture of As biotransformation genes in marine sediments from the East China Sea, which may affect As transformation and the ultimate fate of As in a marine environment.