UNIPROT:Q8NEX9 - FACTA Search

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Query: UNIPROT:Q8NEX9 (reductase)
26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Our previous studies have shown that 2,2-dimethyl-5-t-butyl-1,3-benzodioxole (DBBD), a methylenedioxyphenyl (MDP) analog in which the methylene hydrogens have been replaced by methyl groups, does not form an inhibitory complex with cytochrome P-450 nor induce this cytochrome. However, in the present experiments, DBBD-treated male Dub:ICR mice showed an increase in NADPH-dependent cytochrome c (P-450) reductase and epoxide hydrolase activity. This separation of cytochrome P-450 induction from the induction of epoxide hydrolase and NADPH-dependent cytochrome c (P-450) reductase appears to be unique among inducers of xenobiotic metabolizing enzymes. In similar experiments, mice were treated with phenobarbital + DBBD or 3-methylcholanthrene + DBBD and the following parameters were measured: cytochrome P-450 content; NADPH-dependent reduction of cytochrome c; ethylmorphine and benzphetamine N-demethylase; 7-ethoxycoumarin O-deethylase; benzo[a]pyrene hydroxylase; and ethoxyresorufin O-deethylase. The microsomal proteins were examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Phenobarbital + DBBD treatment gave results which did not differ significantly from those obtained with phenobarbital alone. In contrast, cytochrome P-450 content and benzo[a]pyrene hydroxylase and ethoxyresorufin O-deethylase activities were less in mice treated with 3-methylcholanthrene + DBBD than in animals treated with 3-methylcholanthrene alone. SDS-PAGE confirmed that induction of cytochrome P-450 by 3-methylcholanthrene was reduced by DBBD, suggesting that the latter compound may be an antagonist to the Ah cytosolic receptor.
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PMID:2,2-Dimethyl-5-t-butyl-1,3-benzodioxole: an unusual inducer of microsomal enzymes. 643 15

An NADPH-specific aromatic aldehyde-ketone reductase located in guinea pig liver microsomes can be effectively solubilized with nonionic detergents, but not with bile salts and hydrolytic enzymes. Destruction of microsomal membranes by nonionic detergents or acetone treatment leads to significant activation of the reductase, indicating that the enzyme is partly latent in intact microsomes. After solubilization with Triton X-100, the reductase has been highly purified. The purified enzyme catalyzes the NADPH-linked reduction of xenobiotic aromatic aldehydes and ketones as well as 3-ketosteroids, notably 5 alpha- and 5 beta-dihydrotestosterones. The reductase activities for xenobiotic carbonyl compounds and for 3-ketosteroids are each inhibited by addition of the other type of substrate and show the same pH optimum, cofactor requirement, and heat stability, indicating the same enzyme is responsible for the reduction of the two types of substrates. Hexose-6-phosphate dehydrogenase, purified from guinea pig liver microsomes, acts as a more effective NADPH generator for the reductase than yeast and guinea pig liver cytosolic glucose-6-phosphate dehydrogenase. Evidence has been obtained that hexose-6-phosphate dehydrogenase undergoes a functional interaction with the reductase, facilitating the provision of NADPH to the reductase activity both in the reconstituted system and in microsomes.
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PMID:Microsomal reductase for aromatic aldehydes and ketones in guinea pig liver. Purification, characterization, and functional relationship to hexose-6-phosphate dehydrogenase. 703 Oct 45

The effects of the synthetic dibromo-pyrethroid insecticide deltamethrin on some hepatic phase I and II enzyme activities were studied in rat liver. The animals were treated with daily doses of 5 and 10 mg/kg of both pure insecticide or its commercial formulation (Decis), administered i.p. in corn oil for 7 days. The following enzyme activities were studied: NADPH-cytochrome-P450 reductase, aryl-hydrocarbon hydroxylase, aminopyrine N-demethylase, glutamyl cysteine synthetase, glutathione S-transferase, glutathione peroxidase, peroxisomal acyl-CoA oxidase, catalase, and urate oxidase. Both deltamethrin and its commercial formulation were effective in modifying the activities of several of these hepatic xenobiotic-metabolizing enzymes. However, some differences in enzyme modifications were found between treatment with pure or commercial deltamethrin, the latter being more active. This effect could be ascribed to additives, solvents, and chemical intermediates present in the Decis formulation. These results suggest that exposure to this deltamethrin commercial formulation could be more dangerous than exposure to deltamethrin alone, both in terms of its hepatotoxicity and/or alterations in the hepatic biotransformation of other occupational/environmental xenobiotics.
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PMID:Studies on hepatic xenobiotic-metabolizing enzymes in rats treated with insecticide deltamethrin. 747 74

Activities of the xenobiotic metabolizing enzymes were measured in the liver, kidney, duodenum and lung microsomes and cytosol fractions of Wistar rats after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent bacterial mutagen in chlorinated drinking water. MX was administered by gavage at the dose level of 30 mg/kg for 18 weeks (low dose), or at the dose level which was raised gradually from 45 mg/kg for 7 weeks via 60 mg/kg for 2 weeks to a clearly toxic dose of 75 mg/kg for 5 weeks (high dose). Microsomal and cytosolic preparations were made and the activities of 7-ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-dealkylase (PROD), NADPH-cytochrome-c-reductase, UDP-glucuronosyltransferase (UDPGT) and glutathione-S-transferase (GST) were measured. Kidneys were affected most. A dose-dependent decrease was observed in EROD (90% in males, 80% in females at the high dose) and in PROD (58% in females at the high dose) in kidneys. An increase was, however, detected in kidney NADPH-cytochrome-c-reductase (66% in females at high dose), UDPGT (89% in males and 97% in females at high dose) and GST activities (56% in males and 50% in females at high dose). MX caused only a few changes in the enzyme activities of the liver. The EROD activity was decreased 25% to 37%, both in the livers of males and females, but the total content of P450s was not altered. Hepatic GST activity was elevated in females in a dose-dependent manner (31% and 44%). GST activity was elevated in duodenum in females (59%) at the high dose. There were no marked changes in the enzyme activities in the lungs. MX was a weak inhibitor of EROD activity both in the liver and kidney microsomes in vitro, decreasing the EROD activity by 53% and 43%, respectively at the concentration of 0.9 mM. The results indicate that MX decreases the activity of phase I metabolism enzymes, but induces phase II conjugation enzyme activities, particularly in kidneys in vivo. It is possible that these changes contribute to metabolism of MX in kidneys and renders them susceptible to MX in the course of repeated exposure.
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PMID:Altered enzyme activities of xenobiotic biotransformation in kidneys after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) to rats. 762 69

1. A novel modelling alignment for P450s, utilizing NADPH-P450 reductase for electron transfer, is proposed on the basis of analysis of their amino acid sequences. 2. Information used to facilitate the alignment process includes: the recent X-ray crystal structure of P450102 (P450bm3), site-directed mutagenesis experiments, chemical modification of specific residues, and antibody recognition studies. 3. The alignment has been used to construct a number of microsomal P450s of relevance to xenobiotic and endogenous metabolism.
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PMID:Three-dimensional models of human and other mammalian microsomal P450s constructed from an alignment with P450102 (P450bm3). 764 2

The oxygen reductase and xenobiotic reductase activities of cytochrome P450 (P450) are reviewed. During the oxygen reductase activity of P450, molecular oxygen is reduced to superoxide anion radicals (O2-.) most likely by autooxidation of a P450 ferric-dioxyanion complex. The formation of reactive oxygen species (O2-., hydrogen peroxide, and, notably, hydroxyl free radicals) presents a potential toxication pathway, particularly when effective means of detoxication are lacking. Under anaerobic conditions, P450 may also be involved in the reduction of xenobiotics. During the xenobiotic reductase activity of P450, xenobiotics are reduced by the ferrous xenobiotic complex. After xenobiotic reduction by P450, xenobiotic free radicals are formed that are often capable of reacting directly with tissue macromolecules. Unfortunately, the compounds that are reductively activated by P450 have little structural similarity. The precise molecular mechanism underlying the xenobiotic reductase activity of P450 is, therefore, not yet fully understood. Moreover, description of the molecular mechanisms of xenobiotic and oxygen reduction reactions by P450 is limited by the lack of knowledge of the three-dimensional (3D) structure of the mammalian P450 proteins.
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PMID:Oxygen and xenobiotic reductase activities of cytochrome P450. 773 59

Red blood cells contain many enzymes that are akin to those that catalyze xenobiotic metabolism in liver and other tissues. An obvious exception is the cytochrome P-450 system that is found in virtually all other tissues. In vitro studies, however, have shown that hemoglobin can be a broad monooxygenase catalyst, exhibiting the properties of a monooxygenase enzyme. Thus, catalysis by Hb displays typical Michaelis-Menten kinetics, dependence on the native protein, coupling to NADPH-dependent flavoprotein reductases, and inhibition by carbon monoxide. The reconstituted system containing Hb along with P-450 reductase utilizes NADPH and O2 to catalyze typical monooxygenase reactions, including O- and N-demethylations as well as aromatic and aliphatic hydroxylations, and the catalytic cycle appears to mimic the typical P-450 mechanism. Turnover numbers for aniline hydroxylation are similar for Hb and P-450 reconstituted systems, whereas P-450 systems are more effective for other reactions. Catalysis by Hb seems to be restricted to the beta-heme sites of the tetramer, reflecting more facile substrate access. Overall the similarities and differences between Hb and P-450 provide an opportunity to examine the basis for their differential monooxygenase or peroxidase/peroxygenase activities in a comparative manner. Hb may be especially useful in delineating the early events in the respective reaction schemes, because it can be studied in various stable redox/ligand states, including the oxyferrous form. Similar hemoglobin-catalyzed oxidative biotransformations occur within intact erythrocytes, but apparent turnover numbers are much lower than those with the reconstituted Hb system, suggesting different mechanisms of catalysis. Although Hb-mediated oxidase activity in erythrocytes is low relative to other sites of xenobiotic metabolism, it may contribute to in situ activation of xenobiotics leading to oxidative stress, disruption of sulfhydryl homeostasis in the erythrocytes, covalent modification of Hb, and hemolysis.
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PMID:Hydroxylation and dealkylation reactions catalyzed by hemoglobin. 804 Dec 78

Inhibitors of mammalian cytochrome P450 and P450 reductase were used to investigate the enzymes in flounder (Platichthys flesus) hepatic microsomes involved in the stimulation of NAD(P)H-dependent iron/EDTA-mediated 2-keto-4-methiolbutyric acid (KMBA) oxidation (hydroxyl radical production) by the redox cycling compounds menadione and nitrofurantoin. Inhibitors were first tested for their effects on flounder microsomal P450 and flavoprotein reductase activities. Ellipticine gave type II difference binding spectra (app. Ks 5.36 microM; delta A max 0.16 nmol-1 P450) and markedly inhibited NADPH-cytochrome c reductase, NADPH-cytochrome P450 reductase, and monooxygenase (benzo[a]pyrene metabolism) activities. 3-aminopyridine adenine dinucleotide phosphate (AADP; competitive inhibitor of P450 reductase) inhibited NADPH-cytochrome c but not NADH-cytochrome c or NADH-ferricyanide reductase activities. Alkaline phosphatase (inhibitor of rabbit P450 reductase) stimulated NADPH-cytochrome c reductase activity seven fold but had less effect on NADH-reductase activities. AADP inhibited nitrofurantoin- and menadione-stimulated KMBA oxidation by 45 and 17%, respectively, indicating the involvement of P450 reductase at least in the former. In contrast, ellipticine had relatively little effect, possibly because, unlike cytochrome c, the smaller xenobiotic molecules can access the hydrophilic binding site of P450 reductase. Alkaline phosphatase stimulated NAD(P)H-dependent basal and xenobiotic-stimulated KMBA oxidation, showing general consistency with the results for reductase activities. Overall, the studies indicate both similarities (ellipticine, AADP) and differences (alkaline phosphatase) between the flounder and rat hepatic microsomal enzyme systems.
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PMID:Inhibition studies on the involvement of flavoprotein reductases in menadione- and nitrofurantoin-stimulated oxyradical production by hepatic microsomes of flounder (Platichthys flesus). 807 49

Anthraquinone dyes are utilized by the military in colored-smoke grenades. During production, workers in munitions plants may be exposed to fugitive emissions of these dyes or mixtures thereof. The effects of a prototype violet dye mixture (VDM) consisting of Disperse Red 11 (DR11), [1,4-diamino-2-methoxy-anthraquinone] and Disperse Blue 3 (DB3) [1-methylamino-4-hydroxyethylamino-anthraquinone] on F344 male and female rats have been investigated. Acute 1-day inhalation exposures (6 hr) to VDM were conducted at 1000, 300, 100, 70, 40, and 10 mg/m3, with an additional exposure to 40 mg/m3 6 hr/day for 5 days; 4.22 +/- 2.1 microns (MMAD +/- delta g). Lung burdens of dye, general histopathology, and/or liver function were evaluated at 0, 3, and 7 days postexposure. Unexpected lethality due to severe liver damage was observed with acute exposures of > or = 300 mg/m3 and in the 5-day 40 mg/m3 exposures. Centrilobular degeneration and necrosis of liver cells was concentration-dependent with inhalation of VDM > or = 40 mg/m3. In addition, nasal olfactory epithelium exhibited degeneration and necrosis with acute exposures > or = 10 mg/m3. Lung instillations at 250, 500, and 1000 micrograms of the VDM revealed no lung or liver toxicity. Because per os exposure due to preening was suspected as a major exposure route, a gavage study with the VDM and its two component dyes DR11 and DB3 (800 mg/kg) was undertaken. One day following gavage with DR11 or DB3, serum enzymes indicative of liver toxicity (LDH, SGPT, SDH, and ICDH) were slightly elevated (1-6x control). However, rats gavaged with VDM had serum enzyme levels 10-100x control by Day 1 after gavage, indicating acute liver toxicity. Activities of liver enzymes involved in xenobiotic and glutathione metabolism were also acutely affected. All of the dyes caused various degrees of induction of glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase, and nonprotein sulfhydryls. The enzymes involved in xenobiotic metabolism (glutathione S-transferase, NADPH cytochrome-c reductase, and P450) were also elevated by the two component dyes, in contrast to their significant depression with VDM treatment. The similarity between the liver and olfactory epithelium effects of these compounds and the lack of pulmonary tissue effects is not fully understood, but the interaction of the individual dyes as VDM emphasizes the need to assess chemicals such as the anthraquinones as their likely-to-be-encountered mixtures.
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PMID:Toxicity of an anthraquinone violet dye mixture following inhalation exposure, intratracheal instillation, or gavage. 812 3

The cytotoxicity of polycyclic and monocyclic nitroarenes was tested in cell lines V79/NH, H4IIEC3/G-, 5L and BWI-J, which are distinguished by their specific expression of xenobiotic metabolizing enzymes. The results show that polycyclic nitroarenes differentially affect the test cell lines suggesting that some compounds, such as 1,3-dinitropyrene, are activated by cytochrome P4501A1, others, such as 1,6-dinitropyrene, by reductase(s) and acetyltransferase. No such cell specific responses were seen for 13 monocyclic nitroarenes tested. This group of chemicals apparently is activated by an enzyme(s) other than the polycyclic nitroarenes tested.
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PMID:Toxicity of monocyclic and polycyclic nitroaromatic compounds in a panel of mammalian test cell lines. 820 56

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