The great diversity of reactions catalyzed by cytochromes P450

Cytochrome P450 monooxygenase systems: Diversity and plasticity for adaptive stress response

Superfamily of cytochromes P450 (CYPs) is composed of heme-thiolate-containing monooxygenase enzymes, which play crucial roles in the biosynthesis, bioactivation, and detoxification of a variety of organic compounds, both endogenic and exogenic. Majority of CYP monooxygenase systems are multi-component and contain various redox partners, cofactors and auxiliary proteins, which contribute to their diversity in both prokaryotes and eukaryotes. Recent progress in bioinformatics and computational biology approaches make it possible to undertake whole-genome and phylogenetic analyses of CYPomes of a variety of organisms. Considerable variations in sequences within and between CYP families and high similarity in secondary and tertiary structures between all CYPs along with dramatic conformational changes in secondary structure elements of a substrate binding site during catalysis have been reported. This provides structural plasticity and substrate promiscuity, which underlie functional diversity of CYPs. Gene duplication and mutation events underlie CYP evolutionary diversity and emergence of novel selectable functions, which provide the involvement of CYPs in high adaptability to changing environmental conditions and dietary restrictions. In our review, we discuss the recent advancements and challenges in the elucidating the evolutionary origin and mechanisms underlying the CYP monooxygenase system diversity and plasticity. Our review is in the view of hypothesis that diversity of CYP monooxygenase systems is translated into the broad metabolic profiles, and this has been acquired during the long evolutionary time to provide structural plasticity leading to high adaptative capabilities to environmental stress conditions.

Synthesis and larvicidal efficacy of pyrazolopyrimidine derivatives conjugated with selenium nanoparticles against Culex pipiens L. and Musca domestica L. larvae

The synthesized pyrazolopyrimidine derivatives conjugated with selenium nanoparticles were prepared via a reaction of pyrazolone 1 with aryl-aldehyde and malononitrile or 3-oxo-3-phenylpropanenitrile in the presence ammonium acetate or pipridine using an ultrasonic bath as a modified method in the organic synthesis for such materials. The structure of the synthesized compounds was elucidated through various techniques. All the synthesized pyrazolopyrimidines were used in the synthesis of selenium nanoparticles (SeNPs). These nanoparticles were confirmed using UV-spectra, Dynamic Light scattering and (TEM) techniques. The larvicidal efficiency;of the synthesized;compounds; was investigated against some strains such as Culex pipiens;and Musca domestica larvae. Bioassay test showed pyrazolopyrimide derivatives to exhibit an acceptable larvicidal;bio-efficacy. The derivative (3) exhibited;the highest;efficiency for more than; lab strains of both species. Moreover, C. pipiens larvae were more sensitive towards the examined compounds than M. domestica. The field;strain displayed lower affinity for the 2 folds compounds. Some biochemical changes were tracked through analysis of insect main metabolites (protein, lipid and carbohydrate), in addition to measuring the changes in seven enzymes after treatment. Generally, there was a reduction in the protein, lipids and carbohydrates after treatment with all tested compounds. Moreover, a decrement was noticed for acetylcholine esterase and glutathione;S-transferase; enzymes. There was an increment in the acid;phosphatase; and alkaline phosphatase. In addition, there was elevation in Phenoloxidase level but it noticed the declination in both Cytochrome P450 and Ascorbate peroxidase activity after treatment both flies with derivatives of selenium-nanoparticles in both lab and field strain. Generally, the experiments carried out indicate that antioxidant and detoxification enzymes may play a significant role in mechanism of action of our novel nanocompounds. The cytotoxicity of the synthesized compounds and conjugated with SeNPs showed enhanced compatibility with human normal fibroblast cell line (BJ1) with no toxic effect.

Proteomics-Guided Mining and Characterization of Epoxidase Involved in Camptothecin Biosynthesis from Camptotheca acuminata

The detailed metabolic map for camptothecin (CPT) biosynthesis in Camptotheca acuminata has been proposed according to our combined omics results. However, the CYP450-mediated epoxidation step in CPT biosynthesis remains unexplored. A proteomics-guided approach was used to identify and annotate the proteins enriched during the vigorous CPT metabolism period in mature C. acuminata and seedlings. Comparative analyses revealed that the CPT and flavonoid biosyntheses were vigorous in stems and all of the samples except the leaves, respectively. The CYP71BE genes were screened based on their enrichment patterns at the transcriptomic-proteomic level and biochemically characterized in Saccharomyces cerevisiae WAT11. Four CYP71BE proteins exhibited in vitro isoliquiritigenin epoxidase activity. Additionally, CYP71BE206 showed epoxidase activity toward strictosamide, the critical precursor for CPT biosynthesis, both in vitro and in Nicotiana benthamiana. In planta functional verification suggested that CYP71BE206 is involved in CPT biosynthesis. Their catalytic conditions were optimized, and the enzymatic parameters were determined. This study provides valuable insight into the CYP71BE-mediated epoxidation step for CPT biosynthesis and offers evidence to verify that the newly characterized epoxidase (CYP71BE206) is simultaneously responsible for the biosynthesis of CPT and the flavonoid in this plant. An evolution event probably happened on ancestral CYP71BE, resulting in the neofunctionalization of CYP71BE206.

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Cytochrome P450 Gene, CYP6CX3, Is Involved in the Resistance to Cyantraniliprole in Bemisia tabaci

Bemisia tabaci is an important agricultural sucking pest, and it develops serious resistance to various insecticides. Although cytochrome P450 was involved in the resistance to cyantraniliprole, limited studies have been conducted on B. tabaci. In the present study, piperonyl butoxide significantly increased the toxicity of cyantraniliprole. P450 activities in two resistant populations were 1.97- and 2.17-fold higher than that in the susceptible population. Among 79 P450 genes, CYP6CX3 expressions in two resistant populations were 3.08- and 3.67-fold higher than that in the susceptible population. When CYP6CX3 was knocked down, the toxicity of cyantraniliprole increased significantly. The LC₅₀ value of cyantraniliprole to the Drosophila melanogaster line overexpressing B. tabaci CYP6CX3 increased 7.34-fold. The content of cyantraniliprole was decreased by 25.74 ± 4.27% after mixing with CYP6CX3 and CPR for 2 h. These results suggested that the overexpression of CYP6CX3 was likely involved in the resistance to cyantraniliprole in B. tabaci.

Comparative analysis of the detoxification gene inventory of four major Spodoptera pest species in response to xenobiotics

The genus Spodoptera (Lepidoptera: Noctuidae) comprises some of the most polyphagous and destructive agricultural pests worldwide. The success of many species of this genus is due to their striking abilities to adapt to a broad range of host plants. Superfamilies of detoxification genes play a crucial role in the adaption to overcome plant defense mechanisms mediated by numerous secondary metabolites and toxins. Over the past decade, a substantial amount of expression data in Spodoptera larvae was produced for those genes in response to xenobiotics such as plant secondary metabolites, but also insecticide exposure. However, this information is scattered throughout the literature and in most cases does not allow to clearly identify candidate genes involved in host-plant adaptation and insecticide resistance. In the present review, we analyzed and compiled information on close to 600 pairs of inducers (xenobiotics) and induced genes from four main Spodoptera species: S. exigua, S. frugiperda, S. littoralis and S. litura. The cytochrome P450 monooxygenases (P450s; encoded by CYP genes) were the most upregulated detoxification genes across the literature for all four species. Most of the data was provided from studies on S. litura, followed by S. exigua, S. frugiperda and S. littoralis. We examined whether these detoxification genes were reported for larval survival under xenobiotic challenge in forward and reverse genetic studies. We further analyzed whether biochemical assays were carried out showing the ability of corresponding enzymes and transporters to breakdown and excrete xenobiotics, respectively. This revealed a clear disparity between species and the lack of genetic and biochemical information in S. frugiperda. Finally, we discussed the biological importance of detoxification genes for this genus and propose a workflow to study the involvement of these enzymes in an ecological and agricultural context.

Biochemical and Metabolic Plant Responses toward Polycyclic Aromatic Hydrocarbons and Heavy Metals Present in Atmospheric Pollution

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) are toxic components of atmospheric particles. These pollutants induce a wide variety of responses in plants, leading to tolerance or toxicity. Their effects on plants depend on many different environmental conditions, not only the type and concentration of contaminant, temperature or soil pH, but also on the physiological or genetic status of the plant. The main detoxification process in plants is the accumulation of the contaminant in vacuoles or cell walls. PAHs are normally transformed by enzymatic plant machinery prior to conjugation and immobilization; heavy metals are frequently chelated by some molecules, with glutathione, phytochelatins and metallothioneins being the main players in heavy metal detoxification. Besides these detoxification mechanisms, the presence of contaminants leads to the production of the reactive oxygen species (ROS) and the dynamic of ROS production and detoxification renders different outcomes in different scenarios, from cellular death to the induction of stress resistances. ROS responses have been extensively studied; the complexity of the ROS response and the subsequent cascade of effects on phytohormones and metabolic changes, which depend on local concentrations in different organelles and on the lifetime of each ROS species, allow the plant to modulate its responses to different environmental clues. Basic knowledge of plant responses toward pollutants is key to improving phytoremediation technologies.

Resistance in the Genus Spodoptera: Key Insect Detoxification Genes

The genus Spodoptera (Lepidoptera: Noctuidae) includes species that are among the most important crop pests in the world. These polyphagous species are able to feed on many plants, including corn, rice and cotton. In addition to their ability to adapt to toxic compounds produced by plants, they have developed resistance to the chemical insecticides used for their control. One of the main mechanisms developed by insects to become resistant involves detoxification enzymes. In this review, we illustrate some examples of the role of major families of detoxification enzymes such as cytochromes P450, carboxyl/cholinesterases, glutathione S-transferases (GST) and transporters such as ATP-binding cassette (ABC) transporters in insecticide resistance. We compare available data for four species, Spodoptera exigua, S. frugiperda, S. littoralis and S. litura. Molecular mechanisms underlying the involvement of these genes in resistance will be described, including the duplication of the CYP9A cluster, over-expression of GST epsilon or point mutations in acetylcholinesterase and ABCC2. This review is not intended to be exhaustive but to highlight the key roles of certain genes.

A Proteomics Study on the Mechanism of Nutmeg-Induced Hepatotoxicity

Nutmeg is a traditional spice and medicinal plant with a variety of pharmacological activities. However, nutmeg abuse due to its hallucinogenic characteristics and poisoning cases are frequently reported. Our previous metabolomics study proved the hepatotoxicity of nutmeg and demonstrated that high-dose nutmeg can affect the synthesis and secretion of bile acids and cause oxidative stress. In order to further investigate the hepatotoxicity of nutmeg, normal saline, 1 g/kg, 4 g/kg nutmeg were administrated to male Kunming mice by intragastrical gavage for 7 days. Histopathological investigation of liver tissue, proteomics and biochemical analysis were employed to explore the mechanism of liver damage caused by nutmeg. The results showed that a high-dose (4 g/kg) of nutmeg can cause significant increased level of CYP450s and depletion of antioxidants, resulting in obvious oxidative stress damage and lipid metabolism disorders; but this change was not observed in low-dose group (1 g/kg). In addition, the increased level of malondialdehyde and decreased level of glutathione peroxidase were found after nutmeg exposure. Therefore, the present study reasonably speculates that nutmeg exposure may lead to liver injury through oxidative stress and the degree of this damage is related to the exposure dose.

An Unconventional Melanin Biosynthesis Pathway in Ustilago maydis

Ustilago maydis is a phytopathogenic fungus responsible for corn smut disease. Although it is a very well-established model organism for the study of plant-microbe interactions, its potential to produce specialized metabolites, which might contribute to this interaction, has not been studied in detail. By analyzing the U. maydis genome, we identified a biosynthetic gene cluster whose activation led to the production of a black melanin pigment. Single deletion mutants of the cluster genes revealed that five encoded enzymes are required for the accumulation of the black pigment, including three polyketide synthases (pks3, pks4, and pks5), a cytochrome P450 monooxygenase (cyp4), and a protein with similarity to versicolorin B synthase (vbs1). Metabolic profiles of deletion mutants in this gene cluster suggested that Pks3 and Pks4 act in concert as heterodimers to generate orsellinic acid (OA), which is reduced to the corresponding aldehyde by Pks5. The OA-aldehyde can then react with triacetic acid lactone (TAL), also derived from Pks3/Pks4 heterodimers to form larger molecules, including novel coumarin derivatives. Our findings suggest that U. maydis synthesizes a novel type of melanin based on coumarin and pyran-2-one intermediates, while most fungal melanins are derived from 1,8-dihydroxynaphthalene (DHN) or l-3,4-dihydroxyphenylalanine (l-DOPA). Along with these observations, this work also provides insight into the mechanisms of polyketide synthases in this filamentous fungus.IMPORTANCE The fungus Ustilago maydis represents one of the major threats to maize plants since it is responsible for corn smut disease, which generates considerable economical losses around the world. Therefore, contributing to a better understanding of the biochemistry of defense mechanisms used by U. maydis to protect itself against harsh environments, such as the synthesis of melanin, could provide improved biological tools for tackling the problem and protect the crops. In addition, the fact that this fungus synthesizes melanin in an unconventional way, requiring more than one polyketide synthase for producing melanin precursors, gives a different perspective on the complexity of these multidomain enzymes and their evolution in the fungal kingdom.

Deciphering Reaction Determinants of Altered-Activity CYP2D6 Variants by Well-Tempered Metadynamics Simulation and QM/MM Calculations

The xenobiotic metabolizing enzyme CYP2D6 is the P450 cytochrome family member with the highest rate of polymorphism. This causes changes in the enzyme activity and specificity, which can ultimately lead to adverse reactions during drug treatment. To avoid or lower CYP-related toxicity risks, prediction of the most likely positions within a molecule where a metabolic reaction might occur is paramount. In order to obtain accurate predictions, it is crucial to understand all phenomena within the active site of the enzyme that contribute to an efficient substrate recognition and the subsequent catalytic reaction together with their relative weight within the overall thermodynamic context. This study aims to define the weight of the driving forces upon the C-H bond activation within CYP2D6 wild-type and a clinically relevant allelic variant with increased activity (CYP2D6*53) featuring two amino acid mutations in close vicinity of the heme. First, we investigated the steric and electrostatic complementarity of the substrate bufuralol using well-tempered metadynamics simulations with the aim to obtain the free energy profiles for each site of metabolism (SoM) within the different active sites. Second, the stereoelectronic complementarity was determined for each SoM within the two different active-site environments. Relying on the well-tempered metadynamics simulation energy profiles of each SoM, we identified the binding mode that was closest to the preferred transition-state geometry for efficient C-H bond activation. The binding modes were then used as starting structures for the quantum mechanics/molecular mechanics calculations performed to quantify the corresponding activation barriers. Our results show the relevance of the steric component in orienting the SoM in an energetically accessible position toward the heme. However, the corresponding intrinsic reactivity and electronic complementarity within the active site must be accurately evaluated in order to obtain a meaningful reaction prediction, from which the predominant SoM can be determined. The F120I mutation lowered the activation barrier for the major site and one of the minor SoMs. However, it had an impact neither on the CYP2D6 enantioselectivity preference of the oxidation reaction nor on the stereoselectivity from the substrate point of view.

Identification of novel seed longevity genes related to oxidative stress and seed coat by genome-wide association studies and reverse genetics

Seed longevity is a polygenic trait of relevance for agriculture and for understanding the effect of environment on the ageing of biological systems. In order to identify novel longevity genes, we have phenotyped the natural variation of 270 ecotypes of the model plant, Arabidopsis thaliana, for natural ageing and for three accelerated ageing methods. Genome-wide analysis, using publicly available single-nucleotide polymorphisms (SNPs) data sets, identified multiple genomic regions associated with variation in seed longevity. Reverse genetics of 20 candidate genes in Columbia ecotype resulted in seven genes positive for seed longevity (PSAD1, SSLEA, SSTPR, DHAR1, CYP86A8, MYB47 and SPCH) and five negative ones (RBOHD, RBOHE, RBOHF, KNAT7 and SEP3). In this uniform genetic background, natural and accelerated ageing methods provided similar results for seed-longevity in knock-out mutants. The NADPH oxidases (RBOHs), the dehydroascorbate reductase (DHAR1) and the photosystem I subunit (PSAD1) highlight the important role of oxidative stress on seed ageing. The cytochrome P-450 hydroxylase, CYP86A8, and the transcription factors, MYB47, KNAT7 and SEP3, support the protecting role of the seed coat during seed ageing.

Genome Sequencing Illustrates the Genetic Basis of the Pharmacological Properties of Gloeostereum incarnatum

Gloeostereum incarnatum is a precious edible mushroom that is widely grown in Asia and known for its useful medicinal properties. Here, we present a high-quality genome of G. incarnatum using the single-molecule real-time (SMRT) sequencing platform. The G. incarnatum genome, which is the first complete genome to be sequenced in the family Cyphellaceae, was 38.67 Mbp, with an N50 of 3.5 Mbp, encoding 15,251 proteins. Based on our phylogenetic analysis, the Cyphellaceae diverged ~174 million years ago. Several genes and gene clusters associated with lignocellulose degradation, secondary metabolites, and polysaccharide biosynthesis were identified in G. incarnatum, and compared with other medicinal mushrooms. In particular, we identified two terpenoid-associated gene clusters, each containing a gene encoding a sesterterpenoid synthase adjacent to a gene encoding a cytochrome P450 enzyme. These clusters might participate in the biosynthesis of incarnal, a known bioactive sesterterpenoid produced by G. incarnatum. Through a transcriptomic analysis comparing the G. incarnatum mycelium and fruiting body, we also demonstrated that the genes associated with terpenoid biosynthesis were generally upregulated in the mycelium, while those associated with polysaccharide biosynthesis were generally upregulated in the fruiting body. This study provides insights into the genetic basis of the medicinal properties of G. incarnatum, laying a framework for future characterization of bioactive proteins and pharmaceutical uses of this fungus.

Fungal Cytochrome P450s and the P450 Complement (CYPome) of Fusarium graminearum

Cytochrome P450s (CYPs), heme-containing monooxygenases, play important roles in a wide variety of metabolic processes important for development as well as biotic/trophic interactions in most living organisms. Functions of some CYP enzymes are similar across organisms, but some are organism-specific; they are involved in the biosynthesis of structural components, signaling networks, secondary metabolisms, and xenobiotic/drug detoxification. Fungi possess more diverse CYP families than plants, animals, or bacteria. Various fungal CYPs are involved in not only ergosterol synthesis and virulence but also in the production of a wide array of secondary metabolites, which exert toxic effects on humans and other animals. Although few studies have investigated the functions of fungal CYPs, a recent systematic functional analysis of CYP genes in the plant pathogen Fusarium graminearum identified several novel CYPs specifically involved in virulence, asexual and sexual development, and degradation of xenobiotics. This review provides fundamental information on fungal CYPs and a new platform for further metabolomic and biochemical studies of CYPs in toxigenic fungi.

Immobilized Lignin Peroxidase-Like Metalloporphyrins as Reusable Catalysts in Oxidative Bleaching of Industrial Dyes

Synthetic and bioinspired metalloporphyrins are a class of redox-active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications.

The cytochrome P450 family in the parasitic nematode Haemonchus contortus

Haemonchus contortus, a highly pathogenic and economically important parasitic nematode of sheep, is particularly adept at developing resistance to the anthelmintic drugs used in its treatment and control. The basis of anthelmintic resistance is poorly understood for many commonly used drugs with most research being focused on mechanisms involving drug targets or drug efflux. Altered or increased drug metabolism is a possible mechanism that has yet to receive much attention despite the clear role of xenobiotic metabolism in pesticide resistance in insects. The cytochrome P450s (CYPs) are a large family of drug-metabolising enzymes present in almost all living organisms, but for many years thought to be absent from parasitic nematodes. In this paper, we describe the CYP sequences encoded in the H. contortus genome and compare their expression in different parasite life-stages, sexes and tissues. We developed a novel real-time PCR approach based on partially assembled CYP sequences "tags" and confirmed findings in the subsequent draft genome with RNA-seq. Constitutive expression was highest in larval stages for the majority of CYPs, although higher expression was detected in the adult male or female for a small subset of genes. Many CYPs were expressed in the worm intestine. A number of H. contortus genes share high identity with Caenorhabditis elegans CYPs and the similarity in their expression profiles supports their classification as putative orthologues. Notably, H. contortus appears to lack the dramatic CYP subfamily expansions seen in C. elegans and other species, which are typical of CYPs with exogenous roles. However, a small group of H. contortus genes cluster with the C. elegans CYP34 and CYP35 subfamilies and may represent candidate xenobiotic metabolising genes in the parasite.

Molecular mechanisms of the microsomal mixed function oxidases and biological and pathological implications

The cytochrome P450 mixed function oxidase enzymes play a major role in the metabolism of important endogenous substrates as well as in the biotransformation of xenobiotics. The liver P450 system is the most active in metabolism of exogenous substrates. This review briefly describes the liver P450 (CYP) mixed function oxidase system with respect to its enzymatic components and functions. Electron transfer by the NADPH-P450 oxidoreductase is required for reduction of the heme of P450, necessary for binding of molecular oxygen. Binding of substrates to P450 produce substrate binding spectra. The P450 catalytic cycle is complex and rate-limiting steps are not clear. Many types of chemical reactions can be catalyzed by P450 enzymes, making this family among the most diverse catalysts known. There are multiple forms of P450s arranged into families based on structural homology. The major drug metabolizing CYPs are discussed with respect to typical substrates, inducers and inhibitors and their polymorphic forms. The composition of CYPs in humans varies considerably among individuals because of sex and age differences, the influence of diet, liver disease, presence of potential inducers and/or inhibitors. Because of such factors and CYP polymorphisms, and overlapping drug specificity, there is a large variability in the content and composition of P450 enzymes among individuals. This can result in large variations in drug metabolism by humans and often can contribute to drug–drug interactions and adverse drug reactions. Because of many of the above factors, especially CYP polymorphisms, there has been much interest in personalized medicine especially with respect to which CYPs and which of their polymorphic forms are present in order to attempt to determine what drug therapy and what dosage would reflect the best therapeutic strategy in treating individual patients.

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The CYP P450 system is important in metabolism of endogenous substrates and drugs.

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About 150 forms of CYPs have been identified and they are grouped into families.

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CYPs catalyze a wide variety of reactions and are among the most diverse catalysts known.

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Electrons are passed to the CYP via NADPH+NADPH-cytochrome P450 reductase.

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Metabolism of certain compounds by CYPs generate reactive intermediates which are toxic.

Mass spectrometry based identification of geometric isomers during metabolic stability study of a new cytotoxic sulfonamide derivatives supported by quantitative structure-retention relationships

A set of 15 new sulphonamide derivatives, presenting antitumor activity have been subjected to a metabolic stability study. The results showed that besides products of biotransformation, some additional peaks occurred in chromatograms. Tandem mass spectrometry revealed the same mass and fragmentation pathway, suggesting that geometric isomerization occurred. Thus, to support this hypothesis, quantitative structure-retention relationships were applied. Human liver microsomes were used as an in vitro model of metabolism. The biotransformation reactions were tracked by liquid chromatography assay and additionally, fragmentation mass spectra were recorded. In silico molecular modeling at a semi-empirical level was conducted as a starting point for molecular descriptor calculations. A quantitative structure-retention relationship model was built applying multiple linear regression based on selected three-dimensional descriptors. The studied compounds revealed high metabolic stability, with a tendency to form hydroxylated biotransformation products. However, significant chemical instability in conditions simulating human body fluids was noticed. According to literature and MS data geometrical isomerization was suggested. The developed in sillico model was able to describe the relationship between the geometry of isomer pairs and their chromatographic retention properties, thus it supported the hypothesis that the observed pairs of peaks are most likely geometric isomers. However, extensive structural investigations are needed to fully identify isomers' geometry. An effort to describe MS fragmentation pathways of novel chemical structures is often not enough to propose structures of potent metabolites and products of other chemical reactions that can be observed in compound solutions at early drug discovery studies. The results indicate that the relatively non-expensive and not time- and labor-consuming in sillico approach could be a good supportive tool assisting the identification of cis-trans isomers based on retention data. This methodology can be helpful during the structural identification of biotransformation and degradation products of new chemical entities--potential new drugs.

The mechanisms underlying α-amanitin resistance in Drosophila melanogaster: a microarray analysis

The rapid evolution of toxin resistance in animals has important consequences for the ecology of species and our economy. Pesticide resistance in insects has been a subject of intensive study; however, very little is known about how Drosophila species became resistant to natural toxins with ecological relevance, such as α-amanitin that is produced in deadly poisonous mushrooms. Here we performed a microarray study to elucidate the genes, chromosomal loci, molecular functions, biological processes, and cellular components that contribute to the α-amanitin resistance phenotype in Drosophila melanogaster. We suggest that toxin entry blockage through the cuticle, phase I and II detoxification, sequestration in lipid particles, and proteolytic cleavage of α-amanitin contribute in concert to this quantitative trait. We speculate that the resistance to mushroom toxins in D. melanogaster and perhaps in mycophagous Drosophila species has evolved as cross-resistance to pesticides, other xenobiotic substances, or environmental stress factors.

De novo characterization of transcriptome and gene expression dynamics in epidermis during the larval-pupal metamorphosis of common cutworm

Larval cuticle is degraded and replaced by the pupal counterpart during larval-pupal metamorphosis in the holometabolous insects. In addition to the extrinsic transformation, the epidermis goes through significant changes at molecular levels. To elucidate the intrinsic mechanism of epidermal metamorphosis, the dynamics of chitin content in the cuticle was examined in an important agricultural lepidopteran, the common cutworm, and the transcriptome was analyzed using Illumina sequencing technology. Gene expression profiles during the metamorphosis were further studied by both the digital gene expression (DGE) system and real-time quantitative PCR. The results showed that the chitin content decreased in prepupae and then increased in pupae. A total of 58 million sequencing reads were obtained and assembled into 70,346 unigenes. Over 9000 unigenes were identified to express differentially during the transformation process. As compared with the 6th instar feeding larvae, the most significant changes took place in the proteasome and metabolic pathways in prepupae and pupae, respectively. The cytochrome P450s, VHDLs, chitinase, serine protease and genes involved in sex pheromone biosynthesis changed their mRNA levels remarkably. Three chitinolytic enzymes (chitinase, β-N-acetylglucosaminidase and chitin deacetylase) showed distinct mRNA expression patterns, the former two enzymes revealed the highest expression in prepupae, however the latter one showed its climax mRNA level in pupae. The gene expression patterns suggest that chitinase and β-N-acetylglucosaminidase may be responsible for the degradation of larval cuticles, whereas chitin deacetylase may help to degrade the pupal counterparts. Gene expression dynamics also implied that the chitin of pupal cuticle might be formed by recycling of the degraded chitin of larval cuticle rather than through de novo synthesis. The 20E-induced nuclear receptors seem to be important factors regulating chitin metabolic enzymes during the cuticle remodeling. Our data provide a comprehensive resource for exploring the molecular mechanism of epidermal metamorphosis in insects.

Insights into the Melipona scutellaris (Hymenoptera, Apidae, Meliponini) fat body transcriptome

The insect fat body is a multifunctional organ analogous to the vertebrate liver. The fat body is involved in the metabolism of juvenile hormone, regulation of environmental stress, production of immunity regulator-like proteins in cells and protein storage. However, very little is known about the molecular mechanisms involved in fat body physiology in stingless bees. In this study, we analyzed the transcriptome of the fat body from the stingless bee Melipona scutellaris. In silico analysis of a set of cDNA library sequences yielded 1728 expressed sequence tags (ESTs) and 997 high-quality sequences that were assembled into 29 contigs and 117 singlets. The BLAST X tool showed that 86% of the ESTs shared similarity with Apis mellifera (honeybee) genes. The M. scutellaris fat body ESTs encoded proteins with roles in numerous physiological processes, including anti-oxidation, phosphorylation, metabolism, detoxification, transmembrane transport, intracellular transport, cell proliferation, protein hydrolysis and protein synthesis. This is the first report to describe a transcriptomic analysis of specific organs of M. scutellaris. Our findings provide new insights into the physiological role of the fat body in stingless bees.

Chemical reactions catalyzed by metalloporphyrin-based metal-organic frameworks

The synthetic versatility and the potential application of metalloporphyrins (MP) in different fields have aroused researchers' interest in studying these complexes, in an attempt to mimic biological systems such as cytochrome P-450. Over the last 40 years, synthetic MPs have been mainly used as catalysts for homogeneous or heterogeneous chemical reactions. To employ them in heterogeneous catalysis, chemists have prepared new MP-based solids by immobilizing MP onto rigid inorganic supports, a strategy that affords hybrid inorganic-organic materials. More recently, materials obtained by supramolecular assembly processes and containing MPs as building blocks have been applied in a variety of areas, like gas storage, photonic devices, separation, molecular sensing, magnets, and heterogeneous catalysis, among others. These coordination polymers, known as metal-organic frameworks (MOFs), contain organic ligands or complexes connected by metal ions or clusters, which give rise to a 1-, 2- or 3-D network. These kinds of materials presents large surface areas, Brønsted or redox sites, and high porosity, all of which are desirable features in catalysts with potential use in heterogeneous phases. Building MOFs based on MP is a good way to obtain solid catalysts that offer the advantages of bioinspired systems and zeolitic materials. In this mini review, we will adopt a historical approach to present the most relevant MP-based MOFs applicable to catalytic reactions such as oxidation, reduction, insertion of functional groups, and exchange of organic functions.

Sex differences in body composition, fat storage, and gene expression profile in Caenorhabditis elegans in response to dietary restriction

The metabolic and health-promoting effects of dietary restriction (DR) have been extensively studied in several species. The response to DR with respect to sex is essentially unknown. To address this question, we used the model organism Caenorhabditis elegans to analyze body composition and gene expression in males and hermaphrodites in response to DR. Unexpectedly, DR increased the fat-to-fat-free mass ratio and enlarged lipid droplets in both sexes to a similar extent. These effects were linked to a downregulation of the lipase-like 5 (lipl-5) gene in both sexes at two developmental stages. By contrast, the reductions in body size, protein content, and total RNA content in response to DR were more pronounced in hermaphrodites than in males. Functional enrichment analysis of gene expression data showed a DR-induced downregulation of several embryogenesis-associated genes concomitant with an ongoing expression of sperm-associated genes in hermaphrodites. In conclusion, DR increases fat stores in both sexes of C. elegans in the form of large and possibly lipolysis-resistant lipid droplets and markedly alters the reproductive program in hermaphrodites but not in males.

Clinically significant psychotropic drug-drug interactions in the primary care setting

In recent years, the growing numbers of patients seeking care for a wide range of psychiatric illnesses in the primary care setting has resulted in an increase in the number of psychotropic medications prescribed. Along with the increased utilization of psychotropic medications, considerable variability is noted in the prescribing patterns of primary care providers and psychiatrists. Because psychiatric patients also suffer from a number of additional medical comorbidities, the increased utilization of psychotropic medications presents an elevated risk of clinically significant drug interactions in these patients. While life-threatening drug interactions are rare, clinically significant drug interactions impacting drug response or appearance of serious adverse drug reactions have been documented and can impact long-term outcomes. Additionally, the impact of genetic variability on the psychotropic drug's pharmacodynamics and/or pharmacokinetics may further complicate drug therapy. Increased awareness of clinically relevant psychotropic drug interactions can aid clinicians to achieve optimal therapeutic outcomes in patients in the primary care setting.

Phylogenomics of the benzoxazinoid biosynthetic pathway of Poaceae: gene duplications and origin of the Bx cluster

Background

The benzoxazinoids 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) and 2,4-dihydroxy-7- methoxy-1,4-benzoxazin-3-one (DIMBOA), are key defense compounds present in major agricultural crops such as maize and wheat. Their biosynthesis involves nine enzymes thought to form a linear pathway leading to the storage of DI(M)BOA as glucoside conjugates. Seven of the genes (Bx1-Bx6 and Bx8) form a cluster at the tip of the short arm of maize chromosome 4 that includes four P450 genes (Bx2-5) belonging to the same CYP71C subfamily. The origin of this cluster is unknown.

Results

We show that the pathway appeared following several duplications of the TSA gene (α-subunit of tryptophan synthase) and of a Bx2-like ancestral CYP71C gene and the recruitment of Bx8 before the radiation of Poaceae. The origins of Bx6 and Bx7 remain unclear. We demonstrate that the Bx2-like CYP71C ancestor was not committed to the benzoxazinoid pathway and that after duplications the Bx2-Bx5 genes were under positive selection on a few sites and underwent functional divergence, leading to the current specific biochemical properties of the enzymes. The absence of synteny between available Poaceae genomes involving the Bx gene regions is in contrast with the conserved synteny in the TSA gene region.

Conclusions

These results demonstrate that rearrangements following duplications of an IGL/TSA gene and of a CYP71C gene probably resulted in the clustering of the new copies (Bx1 and Bx2) at the tip of a chromosome in an ancestor of grasses. Clustering favored cosegregation and tip chromosomal location favored gene rearrangements that allowed the further recruitment of genes to the pathway. These events, a founding event and elongation events, may have been the key to the subsequent evolution of the benzoxazinoid biosynthetic cluster.

Novel cytochrome P450, cyp6a17, is required for temperature preference behavior in Drosophila

Perception of temperature is an important brain function for organisms to survive. Evidence suggests that temperature preference behavior (TPB) in Drosophila melanogaster, one of poikilothermal animals, is regulated by cAMP-dependent protein kinase (PKA) signaling in mushroom bodies of the brain. However, downstream targets for the PKA signaling in this behavior have not been identified. From a genome-wide search for the genes regulated by PKA activity in the mushroom bodies, we identified the cyp6a17 Cytochrome P450 gene as a new target for PKA. Our detailed analysis of mutants by genetic, molecular and behavioral assays shows that cyp6a17 is essential for temperature preference behavior. cyp6a17 expression is enriched in the mushroom bodies of the adult brain. Tissue-specific knockdown and rescue experiments demonstrate that cyp6a17 is required in the mushroom bodies for normal temperature preference behavior. This is the first study, to our knowledge, to show PKA-dependent expression of a cytochrome P450 gene in the mushroom bodies and its role as a key factor for temperature preference behavior. Taken together, this study reveals a new PKA-Cytochrome P450 pathway that regulates the temperature preference behavior.

Effect of aflatoxin B1 on nuclear receptors PXR, CAR, and AhR and their target cytochromes P450 mRNA expression in primary cultures of human hepatocytes

Aflatoxin B1 (AFB1), one of the most common mycotoxins found in human foods and animal feed, is principally hepatotoxic and hepatocarcinogenic. The aim of the present study was to explore the effect of AFB1 on messenger RNA (mRNA) expression of pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AhR) and some of their target cytochromes using primary cultures of human hepatocytes. Our results showed that AFB1, at noncytotoxic increasing concentrations, caused a significant upregulation of cytochrome P 2B6 (CYP2B6), CYP3A5, and to a lesser extent CYP3A4 and CYP2C9. Pregnane X receptor and CAR mRNA expression increased in the 3 treated livers. Aflatoxin B1 was found also to induce an overexpression of CYP1A1 and CYP1A2 genes accompanied by an increase in AhR mRNA expression. These findings suggest that AFB1 could activate PXR, CAR, and AhR; however, further investigations are needed to confirm nuclear receptor activation by AFB1.

Characterization of Bacillus thuringiensis L-isoleucine dioxygenase for production of useful amino acids

We determined the enzymatic characteristics of an industrially important biocatalyst, α-ketoglutarate-dependent l-isoleucine dioxygenase (IDO), which was found to be the enzyme responsible for the generation of (2S,3R,4S)-4-hydroxyisoleucine in Bacillus thuringiensis 2e2. Depending on the amino acid used as the substrate, IDO catalyzed three different types of oxidation reactions: hydroxylation, dehydrogenation, and sulfoxidation. IDO stereoselectively hydroxylated several hydrophobic aliphatic l-amino acids, as well as l-isoleucine, and produced (S)-3-hydroxy-l-allo-isoleucine, 4-hydroxy-l-leucine, (S)-4-hydroxy-l-norvaline, 4-hydroxy-l-norleucine, and 5-hydroxy-l-norleucine. The IDO reaction product of l-isoleucine, (2S,3R,4S)-4-hydroxyisoleucine, was again reacted with IDO and dehydrogenated into (2S,3R)-2-amino-3-methyl-4-ketopentanoate, which is also a metabolite found in B. thuringiensis 2e2. Interestingly, IDO catalyzed the sulfoxidation of some sulfur-containing l-amino acids and generated l-methionine sulfoxide and l-ethionine sulfoxide. Consequently, the effective production of various modified amino acids would be possible using IDO as the biocatalyst.

The biology of insecticidal activity and resistance

Identifying insecticide resistance mechanisms is paramount for pest insect control, as the understandings that underpin insect control strategies must provide ways of detecting and managing resistance. Insecticide resistance studies rely heavily on detailed biochemical and genetic analyses. Although there have been many successes, there are also many examples of resistance that still challenge us. As a precursor to rational pest insect control, the biology of the insect, within the contexts of insecticide modes of action and insecticide metabolism, must be well understood. It makes sense to initiate this research in the best model insect system, Drosophila melanogaster, and translate these findings and methodologies to other insects. Here we explore the usefulness of the D. melanogaster model in studying metabolic-based insecticide resistances, target-site mediated resistances and identifying novel insecticide targets, whilst highlighting the importance of having a more complete understanding of insect biology for insecticide studies.

Expression of a novel cytochrome P450 4T gene in rare minnow (Gobiocypris rarus) following perfluorooctanoic acid exposure

Cytochrome P450s play an important role in the biotransformation of endogenous substrates and xenobiotics; however, little is known about the function of the CYP4T subfamily in the transformation of environmental pollutants in fish. We isolated a full-length cDNA sequence (designated as CYP4T11) from rare minnow (Gobiocypris rarus) liver by rapid amplification of cDNA ends. The open reading frame encoded a 467-residue protein that exhibited 87% and 71% identity with zebrafish CYP4T8 and European sea bass CYP4T2, respectively. CYP4T11 was predominantly expressed in liver and intestine with lower expression in the gill and brain. To further examine the function of CYP4T11 in pollutant metabolism, the effects of perfluorooctanoic acid (PFOA) exposure on the transcriptional expression of CYP4T11 and two possible upstream regulators, peroxisome proliferator-activated receptor alpha (PPARalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma), were determined in rare minnow gills and livers. PFOA induced a consistent significant upregulation of both PPARalpha and PPARgamma and a nonsignificant increase of CYP4T11 in the gill. In the liver, induced expression of PPARgamma was observed, although no obvious changes in PPARalpha expression were observed. Induction of CYP4T11 was only observed in males at the highest concentration of PFOA. These results suggest that the PPAR-CYP4T11 signaling pathway may be involved in PFOA-induced gill toxicity. Since the induced expression of CYP4T11 in liver was not consistent with the PPAR regulators, complex tissue-specific transcriptional regulation of CYP4T11 following PFOA exposure likely occurs.

Characterization of Drosophila melanogaster cytochrome P450 genes

Cytochrome P450s form a large and diverse family of heme-containing proteins capable of carrying out many different enzymatic reactions. In both mammals and plants, some P450s are known to carry out reactions essential for processes such as hormone synthesis, while other P450s are involved in the detoxification of environmental compounds. In general, functions of insect P450s are less well understood. We characterized Drosophila melanogaster P450 expression patterns in embryos and 2 stages of third instar larvae. We identified numerous P450s expressed in the fat body, Malpighian (renal) tubules, and in distinct regions of the midgut, consistent with hypothesized roles in detoxification processes, and other P450s expressed in organs such as the gonads, corpora allata, oenocytes, hindgut, and brain. Combining expression pattern data with an RNA interference lethality screen of individual P450s, we identify candidate P450s essential for developmental processes and distinguish them from P450s with potential functions in detoxification.

Engineering and assaying of cytochrome P450 biocatalysts

Cytochrome P450s constitute a highly fascinating superfamily of enzymes which catalyze a broad range of reactions. They are essential for drug metabolism and promise industrial applications in biotechnology and biosensing. The constant search for cytochrome P450 enzymes with enhanced catalytic performances has generated a large body of research. This review will concentrate on two key aspects related to the identification and improvement of cytochrome P450 biocatalysts, namely the engineering and assaying of these enzymes. To this end, recent advances in cytochrome P450 development are reported and commonly used screening methods are surveyed.

The endogenous adrenodoxin reductase-like flavoprotein arh1 supports heterologous cytochrome P450-dependent substrate conversions in Schizosaccharomyces pombe

Mitochondrial cytochromes P450 are essential for biosynthesis of steroid hormones, vitamin D and bile acids. In mammals, the electrons needed for these reactions are provided via adrenodoxin and adrenodoxin reductase (AdR). Recently, Schizosaccharomyces pombe was introduced as a new host for the functional expression of human mitochondrial steroid hydroxylases without the coexpression of their natural redox partners. This fact qualifies S. pombe for the biotechnological production of steroids and for application as inhibitor test organism of heterologously expressed cytochromes P450. In this paper, we present evidence that the S. pombe ferredoxin reductase, arh1, and ferredoxin, etp1fd provide mammalian class I cytochromes P450 with reduction equivalents. The recombinant reductase showed an unusual weak binding of flavin adenine dinucleotide (FAD), which was mastered by modifying the FAD-binding region by site-directed mutagenesis yielding a stable holoprotein. The modified reductase arh1_A18G displayed spectroscopic characteristics similar to AdR and was shown to be capable of accepting electrons with no evident preference for NADH or NADPH, respectively. Arh1_A18G can substitute for AdR by interacting not only with its natural redox partner etp1fd but also with the mammalian homolog adrenodoxin. Cytochrome P450-dependent substrate conversion with all combinations of the mammalian and yeast redox proteins was evaluated in a reconstituted system.

Effects of sediment organic matter quality on bioaccumulation, degradation, and distribution of pyrene in two macrofaunal species and their surrounding sediment

Sediment dwelling macrofauna (infauna) are important vectors for the transfer of sediment-associated contaminants to higher trophic levels. Sedimenting organic matter constitutes an important food source for all benthic organisms and changes seasonally in terms of quantity and quality. Sediment organic matter (SOM) quality affects organism activity and feeding behaviour, and is therefore also likely to affect contaminant fate in benthic systems. We investigated the impact of SOM quality (enrichment with either labile Tetraselmis sp. or refractory lignin) on the accumulation and metabolism of sediment-associated pyrene in Nereis diversicolor (Annelida) and Amphiura filiformis (Echinodermata), as well as the combined effect of SOM quality and infaunal bioturbation on pyrene distribution and metabolism in the sediment. After 45 d of exposure, SOM quality almost doubled pyrene bioaccumulation in both species, while pyrene metabolism remained unaffected. Metabolites comprised approximately 80% of the total tissue pyrene in N. diversicolor and approximately 40% in A. filiformis. A. filiformis arms contained one fifth of the disk pyrene concentration. Approximately 20% of the pyrene found in A. filiformis arms was found to be covalently bound to, e.g. DNA, RNA or proteins, thus reducing pyrene bioavailability to arm-cropping predators. The sedimentary pyrene distribution and metabolism was species-dependent, but correlated poorly with prevailing knowledge on species-specific bioturbation patterns. This was attributed to the comparably high biodegradability of the contaminant thus altering its sorptive characteristics and function as inert tracer. Subduction of pyrene and metabolites occurred, and the fraction of pyrene covalently bound to SOM increased with depth, thereby removing pyrene from the bioavailable pool. Our results imply that bioaccumulation and trophic transfer of sediment-associated PAH should increase following fresh organic matter input, e.g. after sedimentation of phytoplankton blooms. We stress the importance of considering behavioural characteristics of infauna and the trophic situation of the system when assessing fate and effects of sediment-associated contaminants.

Diversification of catalytic function in a synthetic family of chimeric cytochrome p450s

We report initial characterization of a synthetic family of more than 3000 cytochrome P450s made by SCHEMA recombination of 3 bacterial CYP102s. A total of 16 heme domains and their holoenzyme fusions with each of the 3 parental reductase domains were tested for activity on 11 different substrates. The results show that the chimeric enzymes have acquired significant functional diversity, including the ability to accept substrates not accepted by the parent enzymes. K-means clustering analysis of the activity data allowed the enzymes to be classified into five distinct groups based on substrate specificity. The substrates can also be grouped such that one can be a "surrogate" for others in the group. Fusion of a functional chimeric heme domain with a parental reductase domain always reconstituted a functional holoenzyme, indicating that key interdomain interactions are conserved upon reductase swapping.

Cytochrome P450 systems—biological variations of electron transport chains

Cytochromes P450 (P450) are hemoproteins encoded by a superfamily of genes nearly ubiquitously distributed in different organisms from all biological kingdoms. The reactions carried out by P450s are extremely diverse and contribute to the biotransformation of drugs, the bioconversion of xenobiotics, the bioactivation of chemical carcinogens, the biosynthesis of physiologically important compounds such as steroids, fatty acids, eicosanoids, fat-soluble vitamins and bile acids, the conversion of alkanes, terpenes and aromatic compounds as well as the degradation of herbicides and insecticides. Cytochromes P450 belong to the group of external monooxygenases and thus receive the necessary electrons for oxygen cleavage and substrate hydroxylation from different redox partners. The classical as well as the recently discovered P450 redox systems are compiled in this paper and classified according to their composition.

Functional annotation of the Arabidopsis P450 superfamily based on large-scale co-expression analysis

Cytochrome P450 mono-oxygenases play prominent roles in a diverse set of metabolic pathways, but the function of most of these enzymes remains obscure. A bottleneck in the functional genomics of this superfamily constitutes hypothesis generation to identify potential substrates (or substrate classes) individual P450s may act on. We used publicly available large-scale expression data to perform co-expression analysis comparing the expression matrix of each P450 with those from more than 4000 selected genes across thousands of microarrays. Based on functional annotations of co-expressed genes from a diverse set of databases, co-expressed pathways were thus identified for each P450. Using this approach, most P450s with known functions were placed into their respective pathways, thereby proofing the concept. As examples, pathway mapping results identifying novel P450s potentially acting on flower-specific monoterpenes and root-specific triterpenes are described. Co-expression results for all Arabidopsis P450s will be presented as a web resource on the 'CYPedia' web pages (http://ibmp.u-strasbg.fr/CYPedia/).

Fighting fly genes

Fighting by organisms such as mice and Drosophila provides model systems for investigating the genetic basis of aggression. Recent experiments to dissect male aggressive behaviour in Drosophila melanogaster, using gene expression analysis of selected lines followed by mutant analysis, have identified new candidate genes associated with male aggression, including one strong candidate that encodes a cytochrome P450 enzyme. Here, we describe the study of aggressive behaviour in flies and explore the possibility that cytochrome P450 is involved in aggression.

Identification of new participants in the rainbow trout (Oncorhynchus mykiss) oocyte maturation and ovulation processes using cDNA microarrays

BACKGROUND

The hormonal control of oocyte maturation and ovulation as well as the molecular mechanisms of nuclear maturation have been thoroughly studied in fish. In contrast, the other molecular events occurring in the ovary during post-vitellogenesis have received far less attention.

METHODS

Nylon microarrays displaying 9152 rainbow trout cDNAs were hybridized using RNA samples originating from ovarian tissue collected during late vitellogenesis, post-vitellogenesis and oocyte maturation. Differentially expressed genes were identified using a statistical analysis. A supervised clustering analysis was performed using only differentially expressed genes in order to identify gene clusters exhibiting similar expression profiles. In addition, specific genes were selected and their preovulatory ovarian expression was analyzed using real-time PCR.

RESULTS

From the statistical analysis, 310 differentially expressed genes were identified. Among those genes, 90 were up-regulated at the time of oocyte maturation while 220 exhibited an opposite pattern. After clustering analysis, 90 clones belonging to 3 gene clusters exhibiting the most remarkable expression patterns were kept for further analysis. Using real-time PCR analysis, we observed a strong up-regulation of ion and water transport genes such as aquaporin 4 (aqp4) and pendrin (slc26). In addition, a dramatic up-regulation of vasotocin (avt) gene was observed. Furthermore, angiotensin-converting-enzyme 2 (ace2), coagulation factor V (cf5), adam 22, and the chemokine cxcl14 genes exhibited a sharp up-regulation at the time of oocyte maturation. Finally, ovarian aromatase (cyp19a1) exhibited a dramatic down-regulation over the post-vitellogenic period while a down-regulation of Cytidine monophosphate-N-acetylneuraminic acid hydroxylase (cmah) was observed at the time of oocyte maturation.

CONCLUSION

We showed the over or under expression of more that 300 genes, most of them being previously unstudied or unknown in the fish preovulatory ovary. Our data confirmed the down-regulation of estrogen synthesis genes during the preovulatory period. In addition, the strong up-regulation of aqp4 and slc26 genes prior to ovulation suggests their participation in the oocyte hydration process occurring at that time. Furthermore, among the most up-regulated clones, several genes such as cxcl14, ace2, adam22, cf5 have pro-inflammatory, vasodilatory, proteolytics and coagulatory functions. The identity and expression patterns of those genes support the theory comparing ovulation to an inflammatory-like reaction.

Characterization of the P450 monooxygenase NysL, responsible for C-10 hydroxylation during biosynthesis of the polyene macrolide antibiotic nystatin in Streptomyces noursei

The nysL gene, encoding a putative P450 monooxygenase, was identified in the nystatin biosynthetic gene cluster of Streptomyces noursei. Although it has been proposed that NysL is responsible for hydroxylation of the nystatin precursor, experimental evidence for this activity was lacking. The nysL gene was inactivated in S. noursei by gene replacement, and the resulting mutant was shown to produce 10-deoxynystatin. Purification and an in vitro activity assay for 10-deoxynystatin demonstrated its antifungal activity being equal to that of nystatin. The NysL protein was expressed heterologously in Escherichia coli as a His-tagged protein and used in an enzyme assay with 10-deoxynystatin as a substrate. The results obtained clearly demonstrated that NysL is a hydroxylase responsible for the post-polyketide synthase modification of 10-deoxynystatin at position C-10. Kinetic studies with the purified recombinant enzyme allowed determination of K(m) and k(cat) and revealed no inhibition of recombinant NysL by either the substrate or the product. These studies open the possibility for in vitro evolution of NysL aimed at changing its specificity, thereby providing new opportunities for engineered biosynthesis of novel nystatin analogues hydroxylated at alternative positions of the macrolactone ring.

Remarkable substrate-specificity of CYP6AB3 in Depressaria pastinacella, a highly specialized caterpillar

The parsnip webworm, Depressaria pastinacella, a specialist on two genera in Apiaceae, feeds exclusively on the furanocoumarin-containing reproductive structures of its host plants. This caterpillar relies principally on cytochrome P450-mediated detoxification for coping with the high concentrations of furanocoumarins in its diet. A cDNA encoding the furanocoumarin-inducible P450 CYP6AB3 from this species was coexpressed with house-fly NADPH P450 reductase in baculovirus-infected Sf9 cells and tested for binding and metabolism of the six furanocoumarins typically encountered in host plant tissues. Only imperatorin and bergapten bind in close proximity to the catalytic haem and only imperatorin is metabolized (V(max) and K(m) of 2.412 pmol/min per pmol P450 and 94.28 microm, respectively). Purification of the imperatorin metabolite by normal phase HPLC and characterization of its structure by MS-MS analysis indicate that CYP6AB3 initially epoxidizes the carbon-carbon pi-bond on the isoprenyl side chain on imperatorin. An improved molecular model for the CYP6AB3 protein based on this biochemical characterization and the recently defined mammalian CYP3A4 crystal structure provides insight into the remarkable substrate specificity of this protein.

The role of phenylalanine 483 in cytochrome P450 2D6 is strongly substrate dependent

The polymorphic cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of 30% of the drugs currently prescribed, and is thus clinically relevant. Typical CYP2D6 substrates generally contain a basic nitrogen atom and an aromatic moiety adjacent to the site of metabolism. Recently, we demonstrated the importance of active site residue F120 in substrate binding and catalysis in CYP2D6. On the basis of protein homology models, it is claimed that another active site phenylalanine, F483, may also play an important role in the interaction with the aromatic moiety of CYP2D6 substrates. Experimental data to support this hypothesis, however, is not yet available. In fact, in the only study performed, mutation of F483 to isoleucine or tryptophan did not affect the 1'-hydroxylation of bufuralol at all [Smith G, Modi S, Pillai I, Lian LY, Sutcliffe MJ, Pritchard MP, et al., Determinants of the substrate specificity of human cytochrome P-450 CYP2D6: design and construction of a mutant with testosterone hydroxylase activity. Biochem J 1998;331:783-92]. In the present study, the role of F483 in ligand binding and metabolism by CYP2D6 was examined experimentally using site-directed mutagenesis. Replacement of F483 by alanine resulted in a 30-fold lower V(max) for bufuralol 1'-hydroxylation, while the K(m) was hardly affected. The V(max) for 3,4-methylenedioxy-methylamphetamine O-demethylenation on the other hand decreased only two-fold, whereas the effect on the K(m) was much larger. For dextromethorphan, in addition to dextrorphan (O-demethylation) and 3-methoxymorphinan (N-demethylation), two other metabolites were formed that could not be detected for the wild-type. The substrate 7-methoxy-4-(aminomethyl)-coumarin was not metabolised at all by CYP2D6[F483A], a phenomenon that was reported also for CYP2D6[F120A]. The presented data show that next to F120, residue F483 plays a very important role in the metabolism of typical CYP2D6 substrates. The influence of F483 on metabolism was found to be strongly substrate-dependent.

Multiparametric characterization by flow cytometry of flow-sorted subpopulations of a human hepatoma cell line useful for drug research

BACKGROUND

Primary cultured hepatocytes are the closest model to the liver for drug research. However, to overcome its limited availability, the search for hepatic cell lines as an alternative to primary cultures is a matter of current interest. In particular, highly differentiated hepatocellular carcinomas have been proposed as in vitro tools for routine experiments in hepatotoxicity and drug metabolism.

METHODS

Cell populations were selected by fluorescence-activated cell sorting based on low and high relative expressions of P-glycoprotein. These cell lines were characterized after 21 days in culture by multiparametric analysis with flow cytometry providing direct information on key cellular functions (stability in culture, intracellular ionic homeostasis, plasmatic and mitochondrial membrane-related parameters, red-ox status, drug transport, and metabolism).

RESULTS

Two subpopulations (ADV-1 and ADV-2) from the differentiated and well-characterized human hepatoma BC2 cell line showed increased activity of drug transport and drug biotransformation capability (cytochrome P450 [CYP] 1A2, CYP2B6, CYP3A4, and CYP2Cs). These subpopulations were characterized extensively by multiparametric flow cytometric analysis.

CONCLUSION

ADV-1 subpopulation showed greater stability in culture, better efficiency regarding intracellular pH maintenance through the operation of Na+/H+ exchange antiporter, and significantly greater CYP-dependent biotransformation activity than the BC2 parental cells and ADV-2 cells.

Shift to Pseudomonic Acid B Production in P. fluorescens NCIMB10586 by Mutation of Mupirocin Tailoring Genes mupO, mupU, mupV, and macpE

Mupirocin, a polyketide-derived antibiotic from Pseudomonas fluorescens NCIMB10586, is a mixture of pseudomonic acids (PA) that target isoleucyl-tRNA synthase. The mup gene cluster encodes both type I polyketide synthases and monofunctional enzymes that should play a role during the conversion of the product of the polyketide synthase into the active antibiotic (tailoring). By in-frame deletion analysis of selected tailoring open-reading frames we show that mupQ, mupS, mupT, and mupW are essential for mupirocin production, whereas mupO, mupU, mupV, and macpE are essential for production of PA-A but not PA-B. Therefore, PA-B is not simply produced by hydroxylation of PA-A but is either a precursor of PA-A or a shunt product. In the mupW mutant, a new metabolite lacking the tetrahydropyran ring is produced, implicating mupW in oxidation of the 16-methyl group.

Engineering the substrate specificity of cytochrome P450 CYP102A2 by directed evolution: production of an efficient enzyme for bioconversion of fine chemicals

The P450 cytochromes constitute a large family of hemoproteins that catalyze the monooxygenation of a diversity of hydrophobic substrates. CYP102A2 is a catalytically self-sufficient cytoplasmic enzyme from Bacillus subtilis, containing both a monooxygenase domain and a reductase domain on a single polypeptide chain. CYP102A2 was subjected to error-prone PCR to generate mutants with enhanced activity with fatty acids and other aromatic substrates. The library of CYP102A2 mutants was expressed in BL21(DE3) Escherichia coli cells and screened for their ability to oxidize different substrates by means of an activity assay. After a single round of error-prone PCR, the variant Pro15Ser exhibiting modified substrate specificity was generated. This variant showed approximately 6- to 9-fold increased activity with SDS, lauric acid and 1,4-naphthoquinone, and enhanced activity for other substrates such as ethacrynic acid and epsilon-amino-n-caproic acid. Molecular modeling of the CYP102A2 monooxygenase domain suggested that Pro15 is located in a short helical segment and is involved in extensive interactions between the N-terminal domain and the beta2 sheet, which contribute to the formation of the substrate binding site. Thus, Pro15 appears to affect substrate binding and catalysis indirectly. These results clearly demonstrate the importance of remote residues, not readily predicted by rational design, for the determination of substrate specificity. In addition, we report here that the Pro15Ser variant of CYP102A2 can be efficiently immobilized on epoxy-activated Sepharose at pH 8.5 and 4 degrees C. The immobilized variant of CYP102A2 retains most of its activity (81%) and shows improved stability at 37 degrees C. The approach offers the possibility of designing a P450 bioreactor that can be operated over a long period of time with high efficiency and which can be used in fine chemical synthesis.

MAX1 encodes a cytochrome P450 family member that acts downstream of MAX3/4 to produce a carotenoid-derived branch-inhibiting hormone

The plant shoot body plan is highly variable, depending on the degree of branching. Characterization of the max1-max4 mutants of Arabidopsis demonstrates that branching is regulated by at least one carotenoid-derived hormone. Here we show that all four MAX genes act in a single pathway, with MAX1, MAX3, and MAX4 acting in hormone synthesis, and MAX2 acting in perception. We propose that MAX1 acts on a mobile substrate, downstream of MAX3 and MAX4, which have immobile substrates. These roles for MAX3, MAX4, and MAX2 are consistent with their known molecular identities. We identify MAX1 as a member of the cytochrome P450 family with high similarity to mammalian Thromboxane A2 synthase. This, with its expression pattern, supports its suggested role in the MAX pathway. Moreover, the proposed enzymatic series for MAX hormone synthesis resembles that of two already characterized signal biosynthetic pathways: prostaglandins in animals and oxilipins in plants.