Molecular and structural aspects of xenobiotic carbonyl metabolizing enzymes. Role of reductases and dehydrogenases in xenobiotic phase I reactions

Functional analysis of SDR112C1 associated with fenpropathrin tolerance in Tetranychus cinnabarinus (Boisduval)

Short-chain dehydrogenases/reductases (SDRs) are ubiquitously distributed across diverse organisms and play pivotal roles in the growth, as well as endogenous and exogenous metabolism of various substances, including drugs. The expression levels of SDR genes are reportedly upregulated in the fenpropathrin (FEN)-resistant (FeR) strain of Tetranychus cinnabarinus. However, the functions of these SDR genes in acaricide tolerance remain elusive. In this study, the activity of SDRs was found to be significantly higher (2.26-fold) in the FeR strain compared to the susceptible strain (SS) of T. cinnabarinus. A specific upregulated SDR gene, named SDR112C1, exhibited significant overexpression (3.13-fold) in the FeR population compared with that in the SS population. Furthermore, the expression of SDR112C1 showed a significant increase in the response to FEN induction. Additionally, knockdown of the SDR112C1 gene resulted in decreased SDR activity and reduced mite viability against FEN. Importantly, heterologous expression and in vitro incubation assays confirmed that recombinant SDR112C1 could effectively deplete FEN. Moreover, the overexpression of the SDR112C1 gene in Drosophila melanogaster significantly decreased the toxicity of FEN to transgenic fruit flies. These findings suggest that the overexpression of SDR SDR112C1 is a crucial factor contributing to FEN tolerance in T. cinnabarinus. This discovery not only enhances our understanding of SDR-mediated acaricide tolerance but also introduces a new family of detoxification enzymes to consider in practice, beyond cytochrome P450s, carboxyl/choline esterases and glutathione S-transferases.

Isothiocyanates in medicine: A comprehensive review on phenylethyl-, allyl-, and benzyl-isothiocyanates

In recent years, isothiocyanates (ITCs), bioactive compounds primarily derived from Brassicaceae vegetables and herbs, have gained significant attention within the biomedical field due to their versatile biological effects. This comprehensive review provides an in-depth exploration of the therapeutic potential and individual biological mechanisms of the three specific ITCs phenylethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC), and benzyl isothiocyanate (BITC), as well as their collective impact within the formulation of ANGOCIN® Anti-Infekt N (Angocin). Angocin comprises horseradish root (Armoracia rusticanae radix, 80 mg) and nasturtium (Tropaeoli majoris herba, 200 mg) and is authorized for treating inflammatory diseases affecting the respiratory and urinary tract. The antimicrobial efficacy of this substance has been confirmed both in vitro and in various clinical trials, with its primary effectiveness attributed to ITCs. PEITC, AITC, and BITC exhibit a wide array of health benefits, including potent anti-inflammatory, antioxidant, and antimicrobial properties, along with noteworthy anticancer potentials. Moreover, we highlight their ability to modulate critical biochemical pathways, such as the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and signal transducer and activator of transcription (STAT) pathways, shedding light on their involvement in cellular apoptosis and their intricate role to guide immune responses.

New Design of an Activity Assay Suitable for High-Throughput Screening of Substrates and Inhibitors of the Mitochondrial Amidoxime Reducing Component (mARC)

The mitochondrial amidoxime-reducing component (mARC) is one of the simplest molybdenum-containing enzymes. mARC is among a few known reducing enzymes playing an important role in drug metabolism in mammals. Here, an assay based on the fluorescence of NADH is reported for the rapid detection of substrates and potential inhibitors of mARC. So far unknown inhibitors might be useful for the development of drugs assigned to nonalcoholic fatty liver disease (NAFLD) and similar diseases. Kinetics of reactions catalyzed by mARC can be recorded with high sensitivity and precision. On a microtiter plate scale, the assay presented could be applied for high-throughput screening of substance libraries and detection of novel mARC substrate candidates. For instance, molnupiravir was also identified as a new substrate by this assay. For better comparison for such substances, the inhibitor or substrate-to-BAO ratio was introduced. After normalization of enzyme activities to the standard benzamidoxime, substrates can reproducibly be classified.

A review of the molecular mechanisms of acaricide resistance in mites and ticks

The Arachnida subclass of Acari comprises many harmful pests that threaten agriculture as well as animal health, including herbivorous spider mites, the bee parasite Varroa, the poultry mite Dermanyssus and several species of ticks. Especially in agriculture, acaricides are often used intensively to minimize the damage they inflict, promoting the development of resistance. Beneficial predatory mites used in biological control are also subjected to acaricide selection in the field. The development and use of new genetic and genomic tools such as genome and transcriptome sequencing, bulked segregant analysis (QTL mapping), and reverse genetics via RNAi or CRISPR/Cas9, have greatly increased our understanding of the molecular genetic mechanisms of resistance in Acari, especially in the spider mite Tetranychus urticae which emerged as a model species. These new techniques allowed to uncover and validate new resistance mutations in a larger range of species. In addition, they provided an impetus to start elucidating more challenging questions on mechanisms of gene regulation of detoxification associated with resistance.

Enzymatic properties of alcohol dehydrogenase PedE_M.s. derived from Methylopila sp. M107 and its broad metal selectivity

As an important metabolic enzyme in methylotrophs, pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases play significant roles in the global carbon and nitrogen cycles. In this article, a calcium (Ca2+)-dependent alcohol dehydrogenase PedE_M.s., derived from the methylotroph Methylopila sp. M107 was inserted into the modified vector pCM80 and heterologously expressed in the host Methylorubrum extorquens AM1. Based on sequence analysis, PedE_M.s., a PQQ-dependent dehydrogenase belonging to a methanol/ethanol family, was successfully extracted and purified. Showing by biochemical results, its enzymatic activity was detected as 0.72 U/mg while the Km value was 0.028 mM while employing ethanol as optimal substrate. The activity of PedE_M.s. could be enhanced by the presence of potassium (K+) and calcium (Ca2+), while acetonitrile and certain common detergents have been found to decrease the activity of PedE_M.s.. In addition, its optimum temperature and pH were 30°C and pH 9.0, respectively. Chiefly, as a type of Ca2+-dependent alcohol dehydrogenase, PedE_M.s. maintained 60-80% activity in the presence of 10 mM lanthanides and displayed high affinity for ethanol compared to other PedE-type enzymes. The 3D structure of PedE_M.s. was predicted by AlphaFold, and it had an 8-bladed propeller-like super-barrel. Meanwhile, we could speculate that PedE_M.s. contained the conserved residues Glu213, Asn300, and Asp350 through multiple sequence alignment by Clustal and ESpript. The analysis of enzymatic properties of PedE_M.s. enriches our knowledge of the methanol/ethanol family PQQ-dependent dehydrogenase. This study provides new ideas to broaden the application of alcohol dehydrogenase in alcohol concentration calculation, biosensor preparation, and other industries.

The molecular aspects of absorption and metabolism of carotenoids and retinoids in vertebrates

Vitamin A is an essential nutrient necessary for numerous basic physiological functions, including reproduction and development, immune cell differentiation and communication, as well as the perception of light. To evade the dire consequences of vitamin A deficiency, vertebrates have evolved specialized metabolic pathways that enable the absorption, transport, and storage of vitamin A acquired from dietary sources as preformed retinoids or provitamin A carotenoids. This evolutionary advantage requires a complex interplay between numerous specialized retinoid-transport proteins, receptors, and enzymes. Recent advances in molecular and structural biology resulted in a rapid expansion of our understanding of these processes at the molecular level. This progress opened new avenues for the therapeutic manipulation of retinoid homeostasis. In this review, we summarize current research related to the biochemistry of carotenoid and retinoid-processing proteins with special emphasis on the structural aspects of their physiological actions. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Quantitative Prediction of Human Hepatic Clearance for P450 and Non-P450 Substrates from In Vivo Monkey Pharmacokinetics Study and In Vitro Metabolic Stability Tests Using Hepatocytes

Accurate prediction of human pharmacokinetics for drugs remains challenging, especially for non-cytochrome P450 (P450) substrates. Hepatocytes might be suitable for predicting hepatic intrinsic clearance (CL_int) of new chemical entities, because they can be applied to various compounds regardless of the metabolic enzymes. However, it was reported that hepatic CL_int is underestimated in hepatocytes. The purpose of the present study was to confirm the predictability of human hepatic clearance for P450 and non-P450 substrates in hepatocytes and the utility of animal scaling factors for the prediction using hepatocytes. CL_int values for 30 substrates of P450, UDP-glucuronosyltransferase, flavin-containing monooxygenase, esterases, reductases, and aldehyde oxidase in human microsomes, human S9 and human, rat, and monkey hepatocytes were estimated. Hepatocytes were incubated in serum of each species. Furthermore, CL_int values in human hepatocytes were corrected with empirical, monkey, and rat scaling factors. CL_int values in hepatocytes for most compounds were underestimated compared to observed values regardless of the metabolic enzyme, and the predictability was improved by using the scaling factors. The prediction using human hepatocytes corrected with monkey scaling factor showed the highest predictability for both P450 and non-P450 substrates among the predictions using liver microsomes, liver S9, and hepatocytes with or without scaling factors. CL_int values by this method for 80% and 90% of all compounds were within 2- and 3-fold of observed values, respectively. This method is accurate and useful for estimating new chemical entities, with no need to care about cofactors, localization of metabolic enzymes, or protein binding in plasma and incubation mixture.

Functions of aldehyde reductases from Saccharomyces cerevisiae in detoxification of aldehyde inhibitors and their biotechnological applications

Bioconversion of lignocellulosic biomass to high-value bioproducts by fermentative microorganisms has drawn extensive attentions worldwide. Lignocellulosic biomass cannot be efficiently utilized by microorganisms, such as Saccharomyces cerevisiae, but has to be pretreated prior to fermentation. Aldehyde compounds, as the by-products generated in the pretreatment process of lignocellulosic biomass, are considered as the most important toxic inhibitors to S. cerevisiae cells for their growth and fermentation. Aldehyde group in the aldehyde inhibitors, including furan aldehydes, aliphatic aldehydes, and phenolic aldehydes, is identified as the toxic factor. It has been demonstrated that S. cerevisiae has the ability to in situ detoxify aldehydes to their corresponding less or non-toxic alcohols. This reductive reaction is catalyzed by the NAD(P)H-dependent aldehyde reductases. In recent years, detoxification of aldehyde inhibitors by S. cerevisiae has been extensively studied and a huge progress has been made. This mini-review summarizes the classifications and structural features of the characterized aldehyde reductases from S. cerevisiae, their catalytic abilities to exogenous and endogenous aldehydes and effects of metal ions, chemical protective additives, and salts on enzyme activities, subcellular localization of the aldehyde reductases and their possible roles in protection of the subcellular organelles, and transcriptional regulation of the aldehyde reductase genes by the key stress-response transcription factors. Cofactor preference of the aldehyde reductases and their molecular mechanisms and efficient supply pathways of cofactors, as well as biotechnological applications of the aldehyde reductases in the detoxification of aldehyde inhibitors derived from pretreatment of lignocellulosic biomass, are also included or supplemented in this mini-review.

Pharmacokinetics and Pharmacogenomics of Bupropion in Three Different Formulations with Different Release Kinetics in Healthy Human Volunteers

The purpose of this pharmacokinetics (PK) study was to investigate whether different release kinetics from bupropion hydrochloride (HCl) immediate release (IR), sustained release (SR), and extended release (ER) formulations alter its metabolism and to test the hypothesis that the unsuccessful bioequivalence (BE) study of the higher strength (300 mg) of bupropion HCl ER tablets based on the successful BE study of the lower strength (150 mg) was due to metabolic saturation in the gastrointestinal (GI) lumen. A randomized six-way crossover study was conducted in healthy volunteers. During each period, subjects took a single dose of IR (75/100 mg), SR (100/150 mg), or ER (150/300 mg) formulations of bupropion HCl; plasma samples for PK analysis were collected from 0-96 h for all formulations. In addition, each subject's whole blood was collected for the genotyping of various single-nucleotide polymorphisms (SNPs) of bupropion's major metabolic enzymes. The data indicates that the relative bioavailability of the ER formulations was 72.3-78.8% compared with IR 75 mg. No differences were observed for ratio of the area under the curve (AUC) of metabolite to AUC of parent for the three major metabolites. The pharmacogenomics analysis suggested no statistically significant correlation between polymorphisms and PK parameters of the various formulations. Altogether, these data suggested that the different release kinetics of the formulations did not change metabolites-to-parent ratio. Therefore, the differing BE result between the 150 and 300 mg bupropion HCl ER tablets was unlikely due to the metabolic saturation in the GI lumen caused by different release patterns.

Population pharmacokinetics of Daunorubicin in adult patients with acute myeloid leukemia

PURPOSE

Chemotherapy drug resistance and relapse of the disease have been the major factors limiting the success of acute myeloid leukemia (AML) therapy. Several factors, including the pharmacokinetics (PK) of Cytarabine (Ara-C) and Daunorubicin (Dnr), could contribute to difference in treatment outcome in AML.

METHODS

In the present study, we evaluated the plasma PK of Dnr, the influence of genetic polymorphisms of genes involved in transport and metabolism of Dnr on the PK, and also the influence of these factors on clinical outcome. Plasma levels of Dnr and its major metabolite, Daunorubicinol (DOL), were available in 70 adult de novo AML patients. PK parameters (Area under curve (AUC) and clearance (CL)) of Dnr and DOL were calculated using nonlinear mixed-effects modeling analysis performed with Monolix. Genetic variants in ABCB1, ABCG2, CBR1, and CBR3 genes as well as RNA expression of CBR1, ABCB1, and ABCG2 were compared with Dnr PK parameters.

RESULTS

The AUC and CL of Dnr and DOL showed wide inter-individual variation. Patients with an exon1 variant of rs25678 in CBR1 had significantly higher plasma Dnr AUC [p = 0.05] compared to patients with wild type. Patients who achieved complete remission (CR) had significantly lower plasma Dnr AUC, Cmax, and higher CL compared to patients who did not achieve CR.

CONCLUSION

Further validation of these findings in a larger cohort of AML patients is warranted before establishing a therapeutic window for plasma Dnr levels and targeted dose adjustment.

Identification of non-reported bupropion metabolites in human plasma

Bupropion and its three active metabolites exhibit clinical efficacy in the treatment of major depression, seasonal depression and smoking cessation. The pharmacokinetics of bupropion in humans is highly variable. It is not known if there are any non‐reported metabolites formed in humans in addition to the three known active metabolites. This paper reports newly identified and non‐reported metabolites of bupropion in human plasma samples. Human subjects were dosed with a single oral dose of 75 mg of an immediate release bupropion HCl tablet. Plasma samples were collected and analysed by LC–MS/MS at 0, 6 and 24 h. Two non‐reported metabolites (M1 and M3) were identified with mass‐to‐charge (m/z) ratios of 276 (M1, hydration of bupropion) and 258 (M3, hydroxylation of threo/erythrohydrobupropion) from human plasma in addition to the known hydroxybupropion, threo/erythrohydrobupropion and the glucuronidation products of the major metabolites (M2 and M4–M7). These new metabolites may provide new insight and broaden the understanding of bupropion's variability in clinical pharmacokinetics. © 2016 The Authors Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd.

Proteomic changes in Corbicula fluminea exposed to wastewater from a psychiatric hospital

The increase use of pharmaceutical compounds in veterinary practice and human population results in the ubiquitous presence of these compounds in aquatic ecosystems. Because pharmaceuticals are highly bioactive, there is concern about their toxicological effects in aquatic organisms. Therefore, the aim of this study was to assess the effects of an effluent from a psychiatric hospital (containing a complex mixture of 25 pharmaceutical compounds from eleven therapeutic classes) on the freshwater clam Corbicula fluminea using a proteomic approach. The exposure of C. fluminea to this complex effluent containing anxiolytics, analgesics, lipid regulators, beta blockers, antidepressants, antiepileptics, antihistamines, antihypertensives, antiplatelets and antiarrhythmics induced protein changes after 1 day of exposure in clam gills and digestive gland more evident in the digestive gland. These changes included increase in the abundance of proteins associated with structural (actin and tubulin), cellular functions (calreticulin, proliferating cell nuclear antigen (PCNA), T complex protein 1 (TCP1)) and metabolism (aldehyde dehydrogenase (ALDH), alcohol dehydrogenase, 6 phosphogluconate dehydrogenase). Results from this study indicate that calreticulin, PCNA, ALDH and alcohol dehydrogenase in the digestive gland and T complex protein 1 (TCP1)) and 6 phosphogluconate dehydrogenase in the gills represent useful biomarkers for the ecotoxicological characterization of psychiatric hospital effluents in this species.

Discover hidden splicing variations by mapping personal transcriptomes to personal genomes

RNA-seq has become a popular technology for studying genetic variation of pre-mRNA alternative splicing. Commonly used RNA-seq aligners rely on the consensus splice site dinucleotide motifs to map reads across splice junctions. Consequently, genomic variants that create novel splice site dinucleotides may produce splice junction RNA-seq reads that cannot be mapped to the reference genome. We developed and evaluated an approach to identify ‘hidden’ splicing variations in personal transcriptomes, by mapping personal RNA-seq data to personal genomes. Computational analysis and experimental validation indicate that this approach identifies personal specific splice junctions at a low false positive rate. Applying this approach to an RNA-seq data set of 75 individuals, we identified 506 personal specific splice junctions, among which 437 were novel splice junctions not documented in current human transcript annotations. 94 splice junctions had splice site SNPs associated with GWAS signals of human traits and diseases. These involve genes whose splicing variations have been implicated in diseases (such as OAS1), as well as novel associations between alternative splicing and diseases (such as ICA1). Collectively, our work demonstrates that the personal genome approach to RNA-seq read alignment enables the discovery of a large but previously unknown catalog of splicing variations in human populations.

Transcriptomes analysis of Aeromonas molluscorum Av27 cells exposed to tributyltin (TBT): Unravelling the effects from the molecular level to the organism

Aeromonas molluscorum Av27 cells were exposed to 0, 5 and 50 μM of TBT and the respective transcriptomes were obtained by pyrosequencing. Gene Ontology revealed that exposure to 5 μM TBT results in a higher number of repressed genes in contrast with 50 μM of TBT, where the number of over-expressed genes is greater. At both TBT concentrations, higher variations in gene expression were found in the functional categories associated with enzymatic activities, transport/binding and oxidation-reduction. A number of proteins are affected by TBT, such as the acriflavin resistance protein, several transcription-related proteins, several Hsps, ABC transporters, CorA and ZntB and other outer membrane efflux proteins, all of these involved in cellular metabolic processes, important to maintain overall cell viability. Using the STRING tool, several proteins with unknown function were related with others involved in degradation processes, such as the pyoverdine chromophore biosynthetic protein, that has been described as playing a role in the Sn-C cleavage of organotins. This approach has allowed a better understanding of the molecular effects of exposure of bacterial cells to TBT. Furthermore it contributes to the knowledge of the functional genomic aspects of bacteria exposed to this pollutant. Furthermore, the transcriptomic data gathered, and now publically available, constitute a valuable resource for comparative genome analysis.

A Novel Zinc-containing α-Keto Ester Reductase from Actinomycete: An Approach Based on Protein Chemistry and Bioinformatics

We have achieved the purification of an alpha-keto ester reductase (SCKER) from S. coelicolor A3(2) whole cells. SCKER proved to be a homotetramer of 132 kDa containing one equivalent of zinc ion per subunit. The enzyme differed from other alpha-keto ester reductases from microorganisms with regard to subunit structure and metal ion dependency. From a computer search using the protein data banks, the N-terminal amino acid sequence of SCKER was consistent with that of a possible zinc containing alcohol dehydrogenase in S. coelicolor A3(2). None of three hypothetical proteins of S. coelocor A3(2) having a high homology sequence with those of already purified alpha-keto ester reductases from S. thermocyaneoviolaceus [Yamaguchi, H., et al., Biosci. Biotechnol. Biochem., 66, 588-597 (2002)] was identical with that of SCKER.

New hydrocarbon degradation pathways in the microbial metagenome from Brazilian petroleum reservoirs

Current knowledge of the microbial diversity and metabolic pathways involved in hydrocarbon degradation in petroleum reservoirs is still limited, mostly due to the difficulty in recovering the complex community from such an extreme environment. Metagenomics is a valuable tool to investigate the genetic and functional diversity of previously uncultured microorganisms in natural environments. Using a function-driven metagenomic approach, we investigated the metabolic abilities of microbial communities in oil reservoirs. Here, we describe novel functional metabolic pathways involved in the biodegradation of aromatic compounds in a metagenomic library obtained from an oil reservoir. Although many of the deduced proteins shared homology with known enzymes of different well-described aerobic and anaerobic catabolic pathways, the metagenomic fragments did not contain the complete clusters known to be involved in hydrocarbon degradation. Instead, the metagenomic fragments comprised genes belonging to different pathways, showing novel gene arrangements. These results reinforce the potential of the metagenomic approach for the identification and elucidation of new genes and pathways in poorly studied environments and contribute to a broader perspective on the hydrocarbon degradation processes in petroleum reservoirs.

Which metabolites circulate?

Characterization of the circulating metabolites for a new chemical entity in humans is essential for safety assessment, an understanding of their contributions to pharmacologic activities, and their potential involvement in drug-drug interactions. This review examines the abundance of metabolites relative to the total parent drug [metabolite-to-parent (M/P) ratio] from 125 drugs in relation to their structural and physicochemical characteristics, lipoidal permeability, protein binding, and fractional formation from parent (fm). Our analysis suggests that fm is the major determinant of total drug M/P ratio for amine, alcohol, N- and S-oxide, and carboxylic acid metabolites. Passage from the hepatocyte to systemic circulation does not appear to be limiting owing to the vast majority of metabolites formed being relatively lipid permeable. In some cases, active transport plays an important role in this process (e.g., carboxylic acid metabolites). Differences in total parent drug clearance and metabolite clearance are attenuated by the reduction in lipophilicity introduced by the metabolic step and resultant compensatory changes in unbound clearance and protein binding. A small subclass of these drugs (e.g., terfenadine) is unintentional prodrugs with very high parent drug clearance, resulting in very high M/P ratios. In contrast, arenol metabolites show a more complex relationship with fm due largely to the new metabolic routes (conjugation) available to the metabolite compared with the parent drug molecule. For these metabolites, a more thorough understanding of the elimination clearance of the metabolite is critical to discern the likelihood of whether the phenol will constitute a major circulating metabolite.

Significance of reductive metabolism in human intestine and quantitative prediction of intestinal first-pass metabolism by cytosolic reductive enzymes

The number of new drug candidates that are cleared via non-cytochrome P450 (P450) enzymes has increased. However, unlike oxidation by P450, the roles of reductive enzymes are less understood. The metabolism in intestine is especially not well known. The purposes of this study were to investigate the significance of reductive metabolism in human intestine, and to establish a quantitative prediction method of intestinal first-pass metabolism by cytosolic reductive enzymes, using haloperidol, mebendazole, and ziprasidone. First, we estimated the metabolic activities for these compounds in intestine and liver using subcellular fractions. Metabolic activities were detected in human intestinal cytosol (HIC) for all three compounds, and the intrinsic clearance values were higher than those in human liver cytosol for haloperidol and mebendazole. These metabolic activities in HIC were NADPH- and/or NADH-dependent. Furthermore, the metabolic activities for all three compounds in HIC were largely inhibited by menadione, which has been used as a carbonyl reductase (CBR)-selective chemical inhibitor. Therefore, considering subcellular location, cofactor requirement, and chemical inhibition, these compounds might be metabolized by CBRs in human intestine. Subsequently, we tried to quantitatively predict intestinal availability (F(g)) for these compounds using human intestinal S9 (HIS9). Our prediction model using apparent permeability of parallel artificial membrane permeability assay and metabolic activities in HIS9 could predict F(g) in humans for the three compounds well. In conclusion, CBRs might have higher metabolic activities in human intestine than in human liver. Furthermore, our prediction method of human F(g) using HIS9 is applicable to substrates of cytosolic reductive enzymes.

20β-hydroxysteroid dehydrogenase gene promoter: potential role for cyclic AMP and xenobiotic responsive elements

Teleostean 20β-hydroxysteroid dehydrogenase (20β-HSD) is involved in final oocyte maturation and steroid hormone metabolism. It has structural and functional similarities to mammalian carbonyl reductases that are involved in the metabolism of endogenous carbonyl and xenobiotic compounds. To understand the transcriptional regulation of 20β-HSD, here we report the cloning of 20β-HSD promoter from two fish species, rainbow trout and air-breathing catfish. Analysis of the promoter motifs, in silico identified the presence of several sites for transcription factor binding including cAMP, xenobiotic and steroid hormone responsive elements. Luciferase reporter assays with progressive deletion constructs demonstrated that 20β-HSD type B of trout has no promoter activity while 20β-HSD type A of trout and catfish 20β-HSD promoters showed basal promoter activity. A TATA box flanked by a CAAT box is important for basal transcription. Deletion of cAMP responsive element in the promoter decreased basal promoter activity significantly. Reporter assays with forskolin and IBMX, drugs that increase intracellular cAMP induced the promoter activity over the basal level. Intriguingly, β-nafthoflavone, an arylhydrocarbon receptor ligand, induced the 20β-HSD promoter activity and is further evidenced by the induction of 20β-HSD expression in the livers of catfish, in vivo. These results demonstrate for the first time that 20β-HSD expression is not only modulated by cAMP but also by xenobiotics and further studies may provide significance to the ubiquitous distribution and broad substrate specificity of this enzyme.

Crystallization of an atypical short-chain dehydrogenase from Vibrio vulnificus lacking the conserved catalytic tetrad

Short-chain dehydrogenases/reductases (SDRs) are a rapidly expanding superfamily of enzymes that are found in all kingdoms of life. Hallmarked by a highly conserved Asn-Ser-Tyr-Lys catalytic tetrad, SDRs have a broad substrate spectrum and play diverse roles in key metabolic processes. Locus tag VVA1599 in Vibrio vulnificus encodes a short-chain dehydrogenase (hereafter referred to as SDRvv) which lacks the signature catalytic tetrad of SDR members. Structure-based protein sequence alignments have suggested that SDRvv may harbour a unique binding site for its nicotinamide cofactor. To date, structural studies of SDRs with altered catalytic centres are underrepresented in the scientific literature, thus limiting understanding of their spectrum of substrate and cofactor preferences. Here, the expression, purification and crystallization of recombinant SDRvv are presented. Two well diffracting crystal forms could be obtained by cocrystallization in the presence of the reduced form of the phosphorylated nicotinamide cofactor NADPH. The collected data were of sufficient quality for successful structure determination by molecular replacement and subsequent refinement. This work sets the stage for deriving the identity of the natural substrate of SDRvv and the structure-function landscape of typical and atypical SDRs.

Hepatic proteome changes in Solea senegalensis exposed to contaminated estuarine sediments: a laboratory and in situ survey

Assessing toxicity of contaminated estuarine sediments poses a challenge to ecotoxicologists due to the complex geochemical nature of sediments and to the combination of multiple classes of toxicants. Juvenile Senegalese soles were exposed for 14 days in the laboratory and in situ (field) to sediments from three sites (a reference plus two contaminated) of a Portuguese estuary. Sediment characterization confirmed the combination of metals, polycyclic aromatic hydrocarbons and organochlorines in the two contaminated sediments. Changes in liver cytosolic protein regulation patterns were determined by a combination of two-dimensional electrophoresis with de novo sequencing by tandem mass spectrometry. From the forty-one cytosolic proteins found to be deregulated, nineteen were able to be identified, taking part in multiple cellular processes such as anti-oxidative defence, energy production, proteolysis and contaminant catabolism (especially oxidoreductase enzymes). Besides a clear distinction between animals exposed to the reference and contaminated sediments, differences were also observed between laboratory- and in situ-tested fish. Soles exposed in the laboratory to the contaminated sediments failed to induce, or even markedly down-regulated, many proteins, with the exception of a peroxiredoxin (an anti-oxidant enzyme) and a few others, when compared to reference fish. In situ exposure to the contaminated sediments revealed significant up-regulation of basal metabolism-related enzymes, comparatively to the reference condition. Down-regulation of basal metabolism enzymes, related to energy production and gene transcription, in fish exposed in the laboratory to the contaminated sediments, may be linked to sediment-bound contaminants and likely compromised the organisms' ability to deploy adequate responses against insult.

Carbonyl reduction of bupropion in human liver

Bupropion is metabolized extensively in humans by oxidative and reductive processes. CYP2B6 mediates oxidation of bupropion to hydroxybupropion, but the enzyme(s) catalyzing carbonyl reduction of bupropion to erythro- and threohydrobupropion in human liver is unknown. The objective of this study was to examine the enzyme kinetics of bupropion reduction in human liver. In human liver cytosol, the reduction of bupropion to erythro-and threohydrobupropion was NADPH dependent with Cl(int) values of 0.08 and 0.60 µL·min(-1)mg(-1) protein, respectively. Bupropion reduction in liver microsomes was also NADPH dependent with Cl(int) values of 10.4 and 280 µL·min(-1)mg(-1) protein, respectively. Formation of erythro-and threohydrobupropion in microsomes exceeded that in cytosol by 70 and 170 fold, respectively. Menadione, an inhibitor of cytosolic carbonyl reducing enzymes (e.g. CBRs), inhibited erythro-and threohydrobupropion formation in cytosol with IC(50) of 30 and 54 µM, respectively. In microsomes 18β-glycyrrhetinic acid, an inhibitor of microsomal carbonyl reductases (e.g. 11β-HSDs), inhibited their formation with IC(50) of 25 and 26 nM, respectively. Our findings, in agreement with recent human placental studies, show that carbonyl reducing enzymes in hepatic microsomes are significant players in bupropion reduction. Contrary to past studies, we found that threohydrobupropion (not hydroxybupropion) is the major microsomal generated hepatic metabolite of bupropion.

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

Safeners enhance herbicide tolerance in crop plants but not in target weeds, thus improving herbicide selectivity. The safeners isoxadifen-ethyl and mefenpyr-diethyl protect cereal crops from sulfonyl urea herbicides in postemergence application. The two safeners were shown here to induce the cellular xenobiotic detoxification machinery in Arabidopsis thaliana when applied to leaves in a way mimicking field application. Gene expression profiling revealed the induction of 446 genes potentially involved in the detoxification process. Transgenic Arabidopsis plants expressing a reporter gene under control of a safener-responsive maize promoter were used as a model system to study the safener signalling pathway. Reporter gene analysis in the tga2/3/5/6, sid2-2 and npr1 mutants as compared with the wild-type background showed that safener inducibility required TGA transcription factors and salicylic acid (SA) in a NON-EXPRESSOR of PR-1 (NPR1)-independent pathway converging on two as-1 promoter elements. For the majority of the safener-responsive Arabidopsis genes, a similar dependence on TGA transcription factors and/or SA was shown by gene expression profiling in wild-type plants as compared with the tga2/3/5/6 and sid2-2 mutants. Thirty-eight percent of the genes, however, were induced by safeners in a TGA/SA-independent manner. These genes are likely to be controlled by WRKY transcription factors and cognate W-boxes in their promoters.

Bupropion metabolism by human placenta

Smoking during pregnancy is the largest modifiable risk factor for pregnancy-related morbidity and mortality. The success of bupropion for smoking cessation warrants its investigation for the treatment of pregnant patients. Nevertheless, the use of bupropion for the treatment of pregnant smokers requires additional data on its bio-disposition during pregnancy. Therefore, the aim of this investigation was to determine the metabolism of bupropion in placentas obtained from nonsmoking and smoking women, identify metabolites formed and the enzymes catalyzing their formation, as well as the kinetics of the reaction. Data obtained revealed that human placentas metabolized bupropion to hydroxybupropion, erythro- and threohydrobupropion. The rates for formation of erythro- and threohydrobupropion exceeded that for hydroxybupropion by several folds, were dependent on the concentration of bupropion and exhibited saturation kinetics with an apparent K(m) value of 40microM. Human placental 11beta-hydroxysteroid dehydrogenases were identified as the major carbonyl-reducing enzymes responsible for the reduction of bupropion to threo- and erythrohydrobupropion in microsomal fractions. On the other hand, CYP2B6 was responsible for the formation of OH-bupropion. These data suggest that both placental microsomal carbonyl-reducing and oxidizing enzymes are involved in the metabolism of bupropion.

A novel NADPH-dependent aldehyde reductase gene from Saccharomyces cerevisiae NRRL Y-12632 involved in the detoxification of aldehyde inhibitors derived from lignocellulosic biomass conversion

Aldehyde inhibitors such as furfural, 5-hydroxymethylfurfural, anisaldehyde, benzaldehyde, cinnamaldehyde, and phenylaldehyde are commonly generated during lignocellulosic biomass conversion process for low-cost cellulosic ethanol production that interferes with subsequent microbial growth and fermentation. In situ detoxification of the aldehyde inhibitors is possible by the tolerant ethanologenic yeast that involves multiple genes including numerous functional reductases. In this study, we report a novel aldehyde reductase gene clone Y63 from ethanologenic yeast Saccharomyces cerevisiae NRRL Y12632, representing the uncharacterized ORF YGL157W, which demonstrated NADPH-dependent reduction activities toward at least 14 aldehyde substrates. The identity of gene clone Y63 is the same with YGL157W of SGD since a variation of only 35 nucleotides in genomic sequence and three amino acid residues were observed between the two that share the same length of 347 residues in size. As one among the highly induced genes, YGL157W of Y-12632 showed significantly high levels of transcript abundance in response to furfural and HMF challenges. Based on the deduced amino acid sequence and the most conserved functional motif analyses including closely related reductases from five other yeast species to this date, YGL157W was identified as a member of the subclass 'intermediate' of the SDR (short-chain dehydrogenase/reductase) superfamily with the following typical characteristics: the most conserved catalytic site to lie at Tyr(169)-X-X-X-Lys(173); an indispensable reduction catalytic triad at Ser(131), Tyr(169), and Lys(173), and an approved cofactor-binding motif at Gly(11)-X-X-Gly(14)-X-X-Ala(17) near the N-terminus. YGL039W, YDR541C, and YOL151W (GRE2) appeared to be the similar type of enzymes falling into the same category of the intermediate subfamily.

Medium- and short-chain dehydrogenase/reductase gene and protein families : the SDR superfamily: functional and structural diversity within a family of metabolic and regulatory enzymes

Short-chain dehydrogenases/reductases (SDRs) constitute a large family of NAD(P)(H)-dependent oxidoreductases, sharing sequence motifs and displaying similar mechanisms. SDR enzymes have critical roles in lipid, amino acid, carbohydrate, cofactor, hormone and xenobiotic metabolism as well as in redox sensor mechanisms. Sequence identities are low, and the most conserved feature is an α/β folding pattern with a central beta sheet flanked by 2–3 α-helices from each side, thus a classical Rossmannfold motif for nucleotide binding. The conservation of this element and an active site, often with an Asn-Ser-Tyr-Lys tetrad, provides a platform for enzymatic activities encompassing several EC classes, including oxidoreductases, epimerases and lyases. The common mechanism is an underlying hydride and proton transfer involving the nicotinamide and typically an active site tyrosine residue, whereas substrate specificity is determined by a variable C-terminal segment. Relationships exist with bacterial haloalcohol dehalogenases, which lack cofactor binding but have the active site architecture, emphasizing the versatility of the basic fold in also generating hydride transfer-independent lyases. The conserved fold and nucleotide binding emphasize the role of SDRs as scaffolds for an NAD(P)(H) redox sensor system, of importance to control metabolic routes, transcription and signalling.

[Structure and function of peroxisomal tetrameric carbonyl reductase]

In this paper, the structure and function of a new tetrameric carbonyl reductase (TCR) is reviewed. TCRs were purified from rabbit and pig heart, using 4-benzoylpyridine as a substrate. Partial peptide sequencing and cDNA cloning of rabbit and pig TCRs revealed that both enzymes belonged to the short-chain dehydrogenase/reductase family and that their subunits consisted of 260 amino acid residues. Rabbit and pig TCRs catalyzed the reduction of alkyl phenyl ketones, alpha-dicarbonyl compounds, quinones and retinals. Both enzymes were potently inhibited by flavonoids and fatty acids. 9,10-Phenanthrenequinone, which is efficiently reduced by rabbit and pig TCRs, mediated the formation of superoxide radical through its redox cycling in pig heart. The C-terminal sequences of rabbit and pig TCRs comprised a type 1 peroxisomal targeting signal (PTS1) Ser-Arg-Leu, suggesting that the enzymes are localized in the peroxisome. In fact, pig TCR was targeted into the peroxisomal matrix, in the case of transfection of HeLa cells with vectors expressing the enzyme. However, when the recombinant pig TCR was directly introduced into HeLa cells, the enzyme was not targeted into the peroxisomal matrix. The crystal structure of recombinant pig TCR demonstrated that the C-terminal PTS1 of each subunit of the enzyme was buried in the interior of the tetrameric molecule. These findings indicate that pig TCR is imported into the peroxisome as a monomer and then forms an active tetramer within this organelle.

Carbonyl Reductases and Pluripotent Hydroxysteroid Dehydrogenases of the Short-chain Dehydrogenase/reductase Superfamily

Carbonyl reduction of aldehydes, ketones, and quinones to their corresponding hydroxy derivatives plays an important role in the phase I metabolism of many endogenous (biogenic aldehydes, steroids, prostaglandins, reactive lipid peroxidation products) and xenobiotic (pharmacologic drugs, carcinogens, toxicants) compounds. Carbonyl-reducing enzymes are grouped into two large protein superfamilies: the aldo-keto reductases (AKR) and the short-chain dehydrogenases/reductases (SDR). Whereas aldehyde reductase and aldose reductase are AKRs, several forms of carbonyl reductase belong to the SDRs. In addition, there exist a variety of pluripotent hydroxysteroid dehydrogenases (HSDs) of both superfamilies that specifically catalyze the oxidoreduction at different positions of the steroid nucleus and also catalyze, rather nonspecifically, the reductive metabolism of a great number of nonsteroidal carbonyl compounds. The present review summarizes recent findings on carbonyl reductases and pluripotent HSDs of the SDR protein superfamily.

Inhibition of carbonyl reductase activity in pig heart by alkyl phenyl ketones

The inhibitory effects of alkyl phenyl ketones on carbonyl reductase activity were examined in pig heart. In this study, carbonyl reductase activity was estimated as the ability to reduce 4-benzoylpyridine to S(-)-alpha-phenyl-4-pyridylmethanol in the cytosolic fraction from pig heart (pig heart cytosol). The order of their inhibitory potencies was hexanophenone > valerophenone > heptanophenone > butyrophenone > propiophenone. The inhibitory potencies of acetophenone and nonanophenone were much lower. A significant relationship was observed between Vmax/Km values for the reduction of alkyl phenyl ketones and their inhibitory potencies for carbonyl reductase activity in pig heart cytosol. Furthermore, hexanophenone was a competitive inhibitor for the enzyme activity. These results indicate that several alkyl phenyl ketones including hexanophenone inhibit carbonyl reductase activity in pig heart cytosol, by acting as substrate inhibitors.

CBR1 and CBR3 pharmacogenetics and their influence on doxorubicin disposition in Asian breast cancer patients

The present study aimed to identify polymorphic genes encoding carbonyl reductases (CBR1, CBR3) and investigate their influence on doxorubicin disposition in Asian breast cancer patients (n = 62). Doxorubicin (60 mg/m(2)) was administered every 3 weeks for four to six cycles and the pharmacokinetic parameters were estimated using non-compartmental analysis (WinNonlin). The Mann-Whitney U-test was used to assess genotypic-phenotypic correlations. Five CBR1 (-48G>A, c.219G>C, c.627C>T, c.693G>A, +967G>A) and CBR3 (c.11G>A, c.255C>T, c.279C>T, c.606G>A, c.730G>A) polymorphisms were identified. The CBR1 D2 diplotypes were characterized by the presence of at least one variant allele at the c.627C>T and +967G>A loci. Patients in the CBR1 D1 diplotype group had significantly higher clearance (CL) normalized to body surface area (BSA) (CL/BSA[L/h/m(2)]: median 25.09; range 16.44-55.66) and significantly lower exposure levels; area under curve (AUC(0-infinity)/dose/BSA [h/m(5)]; median 15.08; range 6.18-38.03) of doxorubicin compared with patients belonging to the CBR1 D2 diplotype group (CL/BSA[L/h/m(2)]; median 20.88; range 8.68-31.79, P = 0.014; and AUC(0-infinity)/dose/BSA[h/m(5)]; median 21.35; range 9.82-67.17, P = 0.007 respectively). No significant influence of CBR3 polymorphisms on the pharmacokinetics of doxorubicin were observed in Asian cancer patients. The present exploratory study shows that CBR1 D2 diplotypes correlate with significantly higher exposure levels of doxorubicin, suggesting the possibility of lowered intracellular conversion to doxorubicinol in these patients. Further evaluation of carbonyl reductase polymorphisms in influencing the treatment efficacy of doxorubicin-based chemotherapy in Asian cancer patients are warranted.

In vitro characterization of the enzymes involved in the metabolism of 1-furan-2-yl-3-pyridin-2-yl-propenone, an anti-inflammatory propenone compound

Carbonyl reduction is a significant step in the phase I biotransformation of a great variety of aromatic, alicyclic and aliphatic carbonyl compounds. 1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3) has been shown to have anti-inflammatory activity as it inhibits the production of nitric oxide and tumor necrosis factor-beta. In the present study, the metabolic fate and possible involvement of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) and carbonyl reductase (CBR) in the metabolism of FPP-3 were investigated in rat liver subcellular fractions. When FPP-3 was incubated with rat liver subcellular fractions in the presence of beta-NADPH, two major peaks were detected by reduction on the propenone: M1 (1-furan-2-yl-3-pyridin-2-yl-propan-1-one) and M2 (1-furan-2-yl-3-pyridin-2-yl-propan-1-ol). Inhibitors of CBR, such as quercitrin, ethacrynic acid and menadione, significantly increased the formation of M1, but effectively inhibited the formation of M2 in subcellular fractions. Meanwhile, 18beta-glycyrrhetinic acid, a selective inhibitor of 11beta-HSD, marginally inhibited the reduction of FPP-3 in microsomes. A good correlation was observed between the formation of M2 and CBR activity with either 4-pyridine carboxaldehyde (r=0.72) or D,L-glyceraldehyde (r=0.63) as substrates in the cytosol. These results indicated that FPP-3 might be metabolized by cytosolic CBR and uncharacterized microsomal reductase(s) in rat liver.

Modulation of glucocorticoid action and the treatment of type-2 diabetes

The global epidemic of obesity and type-2 diabetes has heightened the need to understand the mechanisms that contribute to its pathogenesis and also to design and trial novel treatments. Patients with glucocorticoid (GC) excess--'Cushing's syndrome'--are phenotypically similar to patients with simple obesity. As such, much research has focused on the manipulation of local GC action as a therapeutic strategy. The majority of the classical actions of GCs are mediated via activation of the glucocorticoid receptor (GR). 11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts inactive cortisone to cortisol and therefore amplifies local GC action. There is now a wealth of data from rodent and clinical studies implicating this conversion in the pathogenesis of obesity, type-2 diabetes, and the metabolic syndrome. Selective 11beta-HSD1 inhibitors (selective in that they block the activity of 11beta-HSD1 and not 11beta-HSD2 which inactivates cortisone to cortisol in mineralocorticoid target tissues) are currently in development although not yet available for use in clinical studies. Rodent studies utilizing these compounds have shown dramatic improvements in insulin sensitivity as well as improvements in lipid profiles and atherogenesis. A further experimental approach has been to design drugs that antagonize GR activation, and again these compounds appear to improve insulin sensitivity and lower glucose production rates. The key test for both of these research strategies is whether they will translate into clinical studies, and results from these trials are now eagerly awaited.

The biochemistry of drug metabolism--an introduction: Part 2. Redox reactions and their enzymes

This review continues a general presentation of the metabolism of drugs and other xenobiotics started in a recent issue of Chemistry & Biodiversity. This Part 2 presents the numerous oxidoreductases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the very diverse reactions they catalyze. Many medicinally, environmentally, and toxicologically relevant examples are presented and discussed. Cytochromes P450 occupy a majority of the pages of Part 2, but a large number of relevant oxidoreductases are also considered, e.g., flavin-containing monooxygenases, amine oxidases, molybdenum hydroxylases, peroxidases, and the innumerable dehydrogenases/reductases.

Carbonyl reductases: the complex relationships of mammalian carbonyl- and quinone-reducing enzymes and their role in physiology

Carbonyl groups are frequently found in endogenous or xenobiotic compounds. Reactive carbonyls, formed during lipid peroxidation or food processing, and xenobiotic quinones are able to covalently modify DNA or amino acids. They can also promote oxidative stress, the products of which are thought to be an important initiating factor in degenerative diseases or cancer. Carbonyl groups are reduced by an array of distinct NADPH-dependent enzymes, belonging to several oxidoreductase families. These reductases often show broad and overlapping substrate specificities and some well-characterized members, e.g., carbonyl reductase (CBR1) or NADPH-quinone reductase (NQO1) have protective roles toward xenobiotic carbonyls and quinones because metabolic reduction leads to less toxic products, which can be further metabolized and excreted. This review summarizes the current knowledge on structure and function relationships of the major human and mammalian carbonyl reductases identified.

Safeners coordinately induce the expression of multiple proteins and MRP transcripts involved in herbicide metabolism and detoxification inTriticum tauschii seedling tissues

Chemicals called safeners protect cereal crops from herbicide toxicity. Proteomic methods (2-D PAGE and LC-MS/MS) were utilized to identify safener- and/or herbicide-regulated proteins in three tissues (root, leaf, and coleoptile) of Triticum tauschii seedlings to better understand a safener's mechanism of action. Growth experiments showed that the safener cloquintocet-mexyl protected seedlings from injury by the herbicide dimethenamid. In total, 29 safener-induced and 10 herbicide-regulated proteins were identified by LC-MS/MS. These proteins were classified into two major categories based on their expression patterns, and were further classified into several functional groups. Surprisingly, mutually exclusive sets of proteins were identified following herbicide or safener treatment, suggesting that different signaling pathways may be recruited. Safener-responsive proteins, mostly involved in xenobiotic detoxification, also included several new proteins that had not been previously identified as safener-responsive, whereas herbicide-regulated proteins belonged to several classes involved in general stress responses. Quantitative RT-PCR revealed that multidrug resistance-associated protein (MRP) transcripts were highly induced by safeners and two MRP genes were differentially expressed. Our results indicate that safeners protect T. tauschii seedlings from herbicide toxicity by coordinately inducing proteins involved in an entire herbicide detoxification pathway mainly in the coleoptile and root, thereby protecting new leaves from herbicide injury.

Stereoselective reduction of 4-benzoylpyridine in the heart of vertebrates

The stereoselectivity in the reduction of 4-benzoylpyridine (4-BP) was examined in the cytosolic fractions from the heart of 9 vertebrates (pig, rabbit, guinea pig, rat, mouse, chicken, soft-shelled turtle, frog and flounder). 4-BP was stereoselectively reduced to S(-)-alpha-phenyl-4-pyridylmethanol [S(-)-PPOL] in the cytosolic fractions from the heart of pig, rabbit and guinea pig. However, of mammalian heart cytsol tested, only rat heart cytosol had little ability to reduce stereoselectively 4-BP. In an attempt to elucidate this reason, amino acid sequence of rat heart carbonyl reductase (RatHCR) was deduced from the cloned cDNA and compared with that of pig heart carbonyl reductase (PigHCR), which shows a high stereoselectivity in the reduction of 4-BP to S(-)-PPOL. RatHCR showed a high identity with PigHCR in amino acid sequence. Furthermore, recombinant RatHCR was confirmed to reduce stereoselectively 4-BP to S(-)-PPOL with a high optical purity comparable to recombinant PigHCR. It is possible that in the cytosolic fraction from the heart of rat, constitutive reductase other than RatHCR counteracts the stereoselective reduction of 4-BP to S(-)-PPOL, by catalyzing the reduction of 4-BP to the R(+)-enantiomer.

Identification of 1-furan-2-yl-3-pyridin-2-yl-propenone, an anti-inflammatory agent, and its metabolites in rat liver subcellular fractions

1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3) has been characterized to have an anti-inflammatory activity through the inhibition of the production of nitric oxide and tumor necrosis factor-alpha. In the present studies, the phase 1 metabolism of FPP-3 was investigated in rat liver microsomes and cytosols. When FPP-3 was incubated with rat liver microsomes and cytosols in the presence of NADPH, 2 major peaks were detected on a liquid chromatography/electrospray ionization-mass spectrometry. Two metabolites (i.e., M1 and M2) were characterized as reduced forms on propenone: M1 (1-furan-2-yl-3-pyridin-2-yl-propan-1-one) was the initial metabolite and M2 (1-furan-2-yl-3-pyridin-2-yl-propan-l-ol) was a secondary alcohol believed to be formed from M1.

Identification of Nrf2-regulated genes induced by chemopreventive isothiocyanate PEITC by oligonucleotide microarray

Electrophiles generated during metabolic activation of carcinogens and reactive oxygen species formed from endogenous and exogenous sources might play a significant role in carcinogenesis. Cancer chemoprevention by induction of phase II detoxifying enzymes to counteract the insults of these reactive intermediates is under intensive investigation. Nrf2, a bZIP transcription factor, plays a central role in the regulation of phase II genes by binding to the antioxidant response element (ARE) in their promoters. Identification of novel Nrf2-regulated genes is likely to provide insight into cellular defense systems against the toxicities of electrophiles and oxidants and may define effective targets for achieving cancer chemoprevention. Phenethyl isothiocyanate (PEITC) is a promising chemopreventive agent that exerts its effects by induction of phase II enzymes via activation of Nrf2. In the present study, a transcriptional profile of liver of the wild-type (Nrf2+/+) and knock-out (Nrf2-/-) mice after treatments with vehicle or PEITC at 3 h and at 12 h was generated using the Affymetrix Mouse Genome 430 2.0 Array. Comparative analysis of gene expression changes between different treatment groups of wild-type and Nrf2-deficient mice facilitated identification of numerous genes regulated by Nrf2. These Nrf2-dependent and PEITC-inducible genes include known detoxication enzymes, as well as novel xenobiotic-metabolizing genes regulated by Nrf2 such as CYP 2c55, CYP 2u1 and aldehyde oxidase. Unexpected clusters included genes for heat shock proteins, ubiquitin/26 S proteasome subunits, and lipid metabolism molecules. Collectively, the identification of these genes not only provides novel insight into the effect of PEITC on global gene expression and chemoprevention, but also reveals the role of Nrf2 in those processes, which would confer cancer chemopreventive future.

Apo- and holo-structures of 3alpha-hydroxysteroid dehydrogenase from Pseudomonas sp. B-0831. Loop-helix transition induced by coenzyme binding

Bacterial 3alpha-hydroxysteroid dehydrogenase, which belongs to a short-chain dehydrogenase/reductase family and forms a dimer composed of two 26-kDa subunits, catalyzes the oxidoreduction of hydroxysteroids in a coenzyme-dependent manner. This enzyme also catalyzes the oxidoreduction of nonsteroid compounds that play an important role in xenobiotic metabolism of bacteria. We performed an x-ray analysis on the crystal of Ps3alphaHSD, the enzyme from Pseudomonas sp. B-0831 complexed with NADH. The resulting crystal structure at 1.8A resolution showed that Ps3alphaHSD exists as a structural heterodimer composed of apo- and holo-subunits. A distinct structural difference between them was found in the 185-207-amino acid region, where the structure in the apo-subunit is disordered whereas that in the holo-subunit consists of two alpha-helices. This fact proved that the NADH binding allows the helical structures to form the substrate binding pocket even in the absence of the substrate, although the region corresponds to the so-called "substrate-binding loop." The induction of alpha-helices in solution by the coenzyme binding was also confirmed by the CD experiment. In addition, the CD experiment revealed that the helix-inducing ability of NADH is stronger than that of NAD. We discuss the negative cooperativity for the coenzyme binding, which is caused by the effect of the structural change transferred between the subunits of the heterodimer.

Determination of 1-furan-2-yl-3-pyridin-2-yl-propenone, an anti-inflammatory propenone compound, by high performance liquid chromatography with ultraviolet spectrometry

1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3) has recently been synthesized and characterized to have an anti-inflammatory activity. In the present study, pharmacokinetic parameters for FPP-3 and its metabolites were determined at the same time by using high-performance liquid chromatography-ultraviolet spectrometry. Two metabolites were detected in sera when FPP-3 was administered intravenously to male SD rats. The linearity of FPP-3, M1 (1-furan-2-yl-3-pyridin-2-yl-propan-1-one) and M2 (1-furan-2-yl-3-pyridin-2-yl-propan-1-ol) was confirmed in the concentration ranges of 0.5-20, 0.101-4.04 and 1.04-20.4 microg/ml, respectively. The lower limits of quantitation of FPP-3, M1 and M2 were 0.5, 0.1 and 1.0 microg/ml, respectively. The intra- and inter-day precision and accuracy over the concentration range of target compounds were within 13.5 and 14.2%, respectively. The half-lives of FPP-3, M1 and M2 were 16.3, 27.7 and 22.1 min, respectively.

An unusual reduction on the quinonoid ring of 5-amino-8-hydroxy-1,4-naphthoquinone by Staphylococcus aureus

AIMS

The objective of this study was to investigate the interactions between 5-amino-8-hydroxy-1,4-naphthoquinone (ANQ) and Staphylococcus aureus.

METHODS AND RESULTS

The compound ANQ display antimicrobial activity against S. aureus. During incubation with 50 microg ml(-1) of ANQ, an unusual reduction reaction takes place and leads to the isolation of 2,3-dihydro-5-amino-8-hydroxy-1,4-naphthoquinone (ANQ-H(2)), fully characterized by means of (13)C-NMR and (1)H-NMR, plus infrared, UV-visible and mass spectroscopy. Oxygen uptake by S. aureus cells was inhibited by ANQ, but in a significantly minor extent by ANQ-H(2).

CONCLUSIONS

The ability of S. aureus to reduce the double bond at C2-C3 of the ANQ is a unusual behaviour for biological transformation of naphthoquinones.

SIGNIFICANCE AND IMPACT OF THE STUDY

This uncommon reaction may provide valuable understanding of the S. aureus regarding to the antimicrobial effect and the acquisition of resistance to naphthoquinones.