Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

If rat liver microsomes are incubated with NADPH and 2-hydroxyestradiol-17beta in vitro, the following is observed: 1. Inhibition of lipid peroxidation, 2.inhibition of cytochrome P-450 reduction, and 3.inhibition of cytochrome b5 reduction. Beyond this the catechole inhibits lipid peroxidation of liposomes in vitro. These phenomena can be explained by interaction of different states of oxidation of the estrogen with the NADPH-cytochrome reductase and with 0-2 radicals, which leads to terminal "uncoupling" of microsomal electron transport.
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PMID:[Effect of 2-hydroxyestradiol-17beta on NADPH-dependent electron transfer in rat liver microsomes in vitro (author's transl)]. 0 67

Hepatic microsomal heme oxygenase was solubilized, partially purified, and characterized from Co2+-treated rats. The enzyme on sodium dodecyl sulfate-polyacrylamide gel electrophoresis exhibited a minimum molecular weight of greater than or equal to 68,000. The solubilized enzyme was totally devoid of contamination with cytochrome P-450 or b5. The requirement for reduced pyridine nucleotides was absolute, and ascorbate could not support heme oxidative activity. However, both TPNH and DPNH could serve as electron donors, with TPNH being more effective. The presence of an appropriate flavoprotein reductase was essential for heme oxidation. The enzyme had an apparent Km of 40 micrometer, a pH optimum of 7.5, and lost substantial activity upon freezing and thawing. Methemoglobin was 30% as effective a substrate for the enzyme as was heme. Free porphyrins could not serve as substrates for the enzyme. The activity of the enzyme was inhibited by HgCl2, p-chloromercuribenzoate, iodoacetamide, mercaptoethanol, and dithiothrietol indicating that free -SH group(s) is necessary for enzyme activity.
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PMID:Solubilization and partial purification of heme oxygenase from rat liver. 1 77

Solubilized NADPH-cytochrome P-450 reductase has been purified from liver microsomes of phenobarbital-treated rats. When added to microsomes, the reductase enhances the monoxygenase, such as aryl hydrocarbon hydroxylase, ethoxycoumarin O-dealkylase, and benzphetamine N-demethylase, activities. The enhancement can be observed with microsomes prepared from phenobarbital- or 3-methylcholanthrene-treated, or non-treated rats. The added reductase is believed to be incorporated into the microsomal membrane, and the rate of the incorporation can be assayed by measuring the enhancement in ethoxycoumarin dealkylase activity. It requires a 30 min incubation at 37 degrees C for maximal incorporation and the process is much slower at lower temperatures. The temperature affects the rate but not the extent of the incorporation. After the incorporation, the enriched microsomes can be separated from the unbound reductase by gel filtration with a Sepharose 4B column. The relationship among the reductase added, reductase bound and the enhancement in hydroxylase activity has been examined. The relationship between the reductase level and the aryl hydrocarbon hydroxylase activity has also been studied with trypsin-treated microsomes. The trypsin treatment removes the reductase from the microsomes, and the decrease in reductase activity is accompanied by a parallel decrease in aryl hydrocarbon hydroxylase activity. When purified reductase is added, the treated microsomes are able to gain aryl hydrocarbon hydroxylase activity to a level comparable to that which can be obtained with normal microsomes. The present study demonstrates that purified NADPH-cytochrome P-450 reductase can be incorporated into the microsomal membrane and the incorporated reductase can interact with the cytochrome P-450 molecules in the membrane, possibly in the same mode as the endogenous reductase molecules. The result is consistent with a non-rigid model for the organization of cytochrome P-450 and NADPH-cytochrome P-450 reductase in the microsomal membrane.
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PMID:Interaction between NADPH-cytochrome P-450 reductase and hepatic microsomes. 2 1

Hepatic microsomal NADPH-cytochrome P-450 reductase was solubilized from rabbit liver microsomes in the presence of detergents and purified to homogeneity by column chromatography. The purified reductase had a molecular weight of 78 000 and contained 1 mol each of FAD and FMN per mol of enzyme. On reduction with NADPH in the presence of molecular oxygen, an 02-stable semiquinone containing one flavin free radical per two flavins was formed, in agreement with previous work on purified trypsin-solubilized reductase. The reduction of oxidized enzyme by NADPH, and autoxidation of NADPH-reduced enzyme by air, proceeded by both one-electron equivalent and two-electron equivalent mechanisms. The reductase reduced cytochrome P-450 (from phenobarbital-treated rabbits) and cytochrome P-448 (from 3-methylcholanthrene-treated rabbits). The rate of reduction of cytochrome P-450 increased in the presence of a substrate, benzphetamine, but that of cytochrome P-448 did not.
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PMID:Studies on the microsomal mixed function oxidase system: redox properties of detergent-solubilized NADPH-cytochrome P-450 reductase. 2 10

Ecdysone 20-monooxygenase, an enzyme which converts ecdysone to ecdysterone (the major moulting hormone of insects) has been characterized in cell-free preparations of tissues from African migratory locust. The product of the reaction has been identified as ecdysterone on the basis of several microchemical derivatization and chromatographic methods. Ecdysone 20-monooxygenase activity is located primarily in the microsomal fraction which also carries NADPH cytochrome c reductase and cytochrome P-450, as shown by sucrose density gradient centrifugation. Optimal conditions for the ecdysone 20-monooxygenase assay have been determined. The enzyme has a Km for ecdysone of 2.7 x 10(-7) M and is competitvely inhibited by ecdysterone (Ki = 7.5 x 10(-7) M). Ecdysone 20-monooxygenase is a typical cytochrome P-450 linked monooxygenase: the reaction requires O2 and is inhibited by CO, an effect partially reversed by white light. The enzyme is effectively inhibited by several specific monooxygenase inhibitors and by sulfhydryl reagents, but not by cyanide ions. Ecdysone elicits a type I difference spectrum when added to oxidized microsomes. NADPH acts as preferential electron donor. The transfer of reducing equivalents proceeds through NADPH cytochrome c (P-450) reductase: ecdysone 20-monooxygenase is inhibited by cytochrome c. Both NADPH cytochrome c reductase and ecdysone 20-monooxygenase are inhibited by NADP+ and show a similar Km for NADPH. The Malpighian tubules have the highest specific activity of ecdysone 20-monooxygenase, while fat body contain most of the cytochrome P-450 and NADPH cytochrome c reductase.
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PMID:Ecdysterone biosynthesis: a microsomal cytochrome-P-450-linked ecdysone 20-monooxygenase from tissues of the African migratory locust. 2 63

Intraperitoneal administration of diazepame and phenazepame into rats /at a dose 50 mg/kg/ within 4 days did not induce liver microsomal enzymes. After administration of chlordiazepoxide at the same dose content of cytochrome P-450 was increased and the rate of dimethylaniline demethylation was elevated. Content of protein as well as NADPH-cytochrome-c-reductase and glucose-6-phosphatase activities were increased after intraperitoneal administration of all the preparations at a dose 100 mg/kg within 4 days. Experiments on the potentiation of hexenal effect demonstrated the decrease in the time of sleep in animals, treated with chlordiazepoxide at a dose 100 mg/kg of body weight.
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PMID:[Effect of 1,4-benzodiazepine tranquilizers on the activity of the hepatocyte hydroxylating complex and glucose-6-phosphatase in white rats]. 4 17

The complex monooxygenatic enzyme exhibits different functional behaviour at different integrational levels, thus indicating distinct organizational states. The aerobic NADPH reduction of microsomes, solubilized and reconstituted systems follows a biphasic kinetics, the two phases are attributed to associated state (cluster) and random cytochrome P-450 reduction. States of different cytochrome P-450/reductase ratio (associates) could not be differentiated in rate. Detergents (Triton N-101, cholate) are capable of disintegrating the system, at last only monophasic slow reduction is observed. The hydroxylation activity follows the respective reduction behaviour. Sedimentation analysis proves the distinct structural states. Reconstitution of the system can be achieved by means of detergent dilution as well as by combining the constituents. The activity of the reconstituted system depends on the composition of the phospholipids as well as on its organizational state. The reassociation of the solubilized enzyme system at nearly microsomal components stoichiometry (Triton N-101 dilution) proves to be thermodynamically governed leading to self-organization of the system without matrix prerequisite. Individual step rate constants of the reduction reaction and other system parameters are accessible by means of a model treatment of the disintegrated system. Further application to mixed kinetics systems is in progress.
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PMID:NADPH reduction of cytochrome P-450 at different integrational levels of the enzyme system. 4 48

Recent investigations in this laboratory on the mechanism of action of liver microsomal cytochrome P-450 (P-450 LM) and its interaction with other components of the hydroxylation system are presented. Two electrophoretically homogeneous forms of the cytochrome, phenobarbital-inducible P-450 LM2 and 5,6-benzoflavone-inducible P-450 LM4, so designated according to their relative electrophoretic mobilities, were used in these studies. Phosphatidylcholine is required in the reconstituted enzyme system for rapid electron transfer from NADPH to P-450 LM, catalyzed by NADPH-cytochrome P-450 reductase, as well as for maximal hydroxylation activity with either molecular oxygen or a peroxy compound serving as oxygen donor to the substrate. The phospholipid facilitates the binding of both substrate and reductase to P-450 LM and apparently causes a structural change in the cytochrome as shown by an increase in alpha-helical content, determined by circular dichroic spectrometry. P-450LM3 and LM4 are one-electron acceptors under anaerobic conditions, in accord with previous potentiometric titrations and product yield data, but in disagreement with previous titrations with reducing agents. The cause for the discrepancy between the present and earlier results is not yet fully understood. Stopped flow spectrophotometry was employed to detect intermediates in the reaction of peroxy compounds with P-450LM2. With m-chloroperbenzoic acid the intermediate formed has absorption maxima at 375, 425, and 540 nm in the absolute spectrum and at 370, 436, and 540 nm in the difference spectrum (intermediate minus oxidized form). A study of the magnitude of the spectral change at various peracid concentrations indicated that with this oxidant the reaction shows a dependence resembling a binding curve. These and other experiments with various oxidants, including cumente hydroperoxide, suggest a reversible two-step mechanism according to the reaction: P-450 LM + oxidant equilibrium C equilibrium D, where C may be an enzyme-oxidant complex and D is a spectral intermediate of unknown structure. A scheme is proposed for the mechanism of action of P-450 LM based on these and earlier studies, including evidence from deuterium isotope experiments for the formation of a substrate carbon radical prior to oxygen transfer.
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PMID:Mechanistic studies with purified components of the liver microsomal hydroxylation system: spectral intermediates in reaction of cytochrome P-450 with peroxy compounds. 4 50

Carbon monoxide inhibited the carbon tetrachloride-induced NADPH oxidation rate. The addition of methylviologen to the incubation mixture under the atmosphere of nitrogen resulted in the enhancement of the reductase activity of microsomes for carbon tetrachloride, as determined by chloroform formation. The addition of methylviologen also enhanced the carbon tetrachloride-induced loss of cytochrome P-450, while the apparent content of cytochrome b5 and the activity of NADPH-cytochrome c reductase remained unchanged. Under a strong inhibition of lipid peroxidation by addition of EDTA, carbon tetrachloride induced a clear loss of cytochrome P-450 to the extent similar to that seen in the absence of EDTA. These results indicate that cytochrome P-450 is directly degraded in association with the reductive metabolism of carbon tetrachloride by cytochrome P-450.
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PMID:The apparent loss of cytochrome P-450 associated with metabolic activation of carbon tetrachloride. 4 18

Studies were conducted to determine the in vivo effect of acetaminophen (AAP) on the lipid peroxidation, drug metabolizing enzyme activity and microsomal electron transfer system of rat and mouse liver. AAP was found to inhibit ethylmorphine N-demethylase activity in the presence of NADPH and this inhibition of the enzyme was due to decrease in cytochrome P-450 content, but not due to change in lipid peroxidation in liver microsomes. Kinetical data showed that AAP administration had no effect on Km values of ethylmorphine N-demethylase, however, a decrease in the Vmax values was seen in rats and mice. There was no significant effect of AAP on both NADPH-cytochrome c reductase and the content of cytochrome b5 3 hours after this administration to rats and mice. On the other hand, AAP induced a significant decrease in NADH-ferricyanide reductase in mice, but not in rats. The greatest decrease in cytochrome P-450 observed among the components of the liver microsomal electron transfer system of rats and mice.
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PMID:Comparison of effects of acetaminophen on liver microsomal drug metabolism and lipid peroxidation in rats and mice. 10 Jun 39


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