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)

Fluorescence quenching of benzo[a]pyrene (BP) by cytochrome P450c was used to probe this substrate-enzyme binding interaction. Addition of NADPH-cytochrome P450 reductase, an essential electron carrier during P450 catalysis, resulted in increased quenching and thus strengthened binding of BP to P450c. This shows that the role of reductase extends beyond that of an electron transfer agent to influence substrate binding. Fluorescence titration measurements revealed that reductase and P450c formed a complex with an apparent KD of 13.7 +/- 0.9 nM. Reductase had no effect in the presence of an anti-P450c monoclonal antibody which inhibits BP hydroxylation, which suggests that this monoclonal antibody binds P450c near its reductase binding region.
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PMID:A fluorescence study of the interactions of benzo[a]pyrene, cytochrome P450c and NADPH-cytochrome P450 reductase. 190 75

The recent determination of the amino acid sequences of the Bacillus megaterium cytochrome P-450 and the flavoprotein component of Salmonella typhimurium NADPH-sulfite reductase revealed that these enzymes contain a flavoprotein moiety remarkably similar to mammalian NADPH-cytochrome P-450 reductase. The presence of this oxidoreductase in these very different enzymes suggests that this flavoprotein arose early in evolution and was utilized as an enzymological building block. The multi-domain structure of the reductase further suggests that it arose through a fusion of genes encoding simple flavin electron-transport proteins.
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PMID:An unusual yet strongly conserved flavoprotein reductase in bacteria and mammals. 190 7

About 30 antitumor anthracycline antibiotics were tested for their susceptibilities to reductive deglycosidation at C-7 catalyzed by rat liver microsomal NADPH-cytochrome P-450 reductase, xanthine oxidase, cytochrome C reductase and DT-diaphorase. Enzymatic activities to reduce the C-7 position of anthracycline antibiotics were similar among the four redox enzymes although a few exceptions were observed with DT-diaphorase. Among therapeutic use of anthracyclines, aclacinomycin A (ACM-A, aclarubicin) and daunomycin (daunorubicin) were found to be highly sensitive to the redox enzymes tested while adriamycin (ADM, doxorubicin) and THP-ADM (pirarubicin) were resistant to enzymatic reductive deglycosidation. When glycosidic and hydroxylated analogs of ACM-A were compared it was found that anthracyclines with smaller glycoside residues were more sensitive to the redox enzymes and the presence of hydroxyl groups on the aglycone moiety decreased the reductive deglycosidation activities. Thus, the aglycone, aklavinone, was most rapidly reduced to 7-deoxyaklavinone. 1-Hydroxy-, 2-hydroxy-, 11-hydroxy- and 1,11-dihydroaclacinomycins A were more resistant to the redox enzymes that ACM-A. Especially, 2-hydroxyaclacinomycins were completely insensitive to the enzymatic reduction. THP-ADM, 4'-substituted analog of ADM, was more resistant to the redox enzymes than ADM itself. These results show that the presence of a hydroxyl group, its position on aglycone, the presence of 4'-substituent on aminosugar and its length in the anthracycline molecule play important roles on the C-7 reduction by the redox enzymes. Relationship between reductive deglycosidation susceptibilities and cell-growth inhibitory activities of anthracycline antibiotics are also discussed.
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PMID:Structure-sensitivity relationship of anthracycline antibiotics to C7-reduction by redox enzymes. 190 11

Rat liver cytochrome P-450IA1 and/or yeast NADPH-cytochrome P-450 reductase was expressed genetically in yeast microsomes. The ratio of P-450IA1 to the reductase was about 17:1 and 1:2 without and with coexpression of the reductase, respectively. Rotational diffusion of P-450IA1 was examined by observing the flash-induced absorption anisotropy, r(t), of the heme.CO complex. In only P-450IA1-expressed microsomes, 28% of P-450IA1 was rotating with a rotational relaxation time (phi) of about 1200 microseconds. The mobile population was increased to 43% by the presence of the coexpressed reductase, while phi was not changed significantly. Increased concentration of KCl from 0 to 1000 mM caused considerable mobilization of P-450IA1. The results demonstrate a proper incorporation of P-450IA1 molecules into yeast microsomal membranes. The significant mobilization of P-450IA1 by the presence of reductase suggests a possible transient association of P-450IA1 with the reductase.
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PMID:Rotation and interactions of genetically expressed cytochrome P-450IA1 and NADPH-cytochrome P-450 reductase in yeast microsomes. 190 75

The amino acids of cytochrome P450 reductase involved in the interaction with cytochrome P450 were identified with a differential labeling technique. The water-soluble carbodiimide EDC (1-ethyl-3-[3- (dimethylamino)propyl]-carbodiimide) was used with the nucleophile methylamine to modify carboxyl residues. When the modification was performed in the presence of cytochrome P450, there was no inhibition in the ability of the modified reductase to bind to cytochrome P450. However, subsequent modification of the reductase in the absence of cytochrome P450 caused a fourfold increase in the Km and an 80% decrease in kcat/Km (relative to the reductase modified in the first step), for the interaction with cytochrome P450. These effects are attributed to the modification of approximately 3.2 mol of carboxyl residues per mole of reductase. Tryptic peptides generated from the modified reductase were purified by reverse phase high-performance liquid chromatography and characterized. Amino acid sequencing and analysis suggest that the peptide which contains approximately 40% of the labeled carboxyl residues corresponds to amino acid residues 109-130 of rat liver NADPH-cytochrome P450 reductase. One or more of the seven carboxyl containing amino acids within this peptide is presumably involved in the interaction with cytochrome P450.
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PMID:Identification and characterization of an NADPH-cytochrome P450 reductase derived peptide involved in binding to cytochrome P450. 192 97

Bovine heart microsomes have been found to contain a non-heme iron protein which serves as an electron acceptor for NADPH-cytochrome P-450 reductase and therefore stimulates NADPH oxidation. This protein, tentatively referred to as Microsomal Iron Protein (MIP), has been extracted with Triton N-101 and purified by ion exchange chromatography on CM- and DEAE-celluloses and gel filtration on Sepharose 6B. MIP is an Mr = 66,000 monomer with 17 atoms of Fe(III)/molecule. Incubation with dithionite removes iron from MIP and abolishes the stimulation of NADPH oxidation, but subsequent incubation with nitrilotriacetic-Fe(III) reincorporates iron and restores the stimulation of NADPH oxidation. Oxygen is the ultimate electron acceptor. In the presence of oxygen, the enzymatic reduction of MIP Fe(III) is followed by the reoxidation of Fe(II) at the expense of oxygen, generating superoxide anion and regenerating MIP Fe(III) for the continuous oxidation of NADPH. In the absence of oxygen, electron transfer from the reductase to MIP Fe(III) causes the release of Fe(II), which limits the ability of MIP to serve as an electron acceptor and stimulate NADPH oxidation. The--NH2-terminal of MIP has been sequenced, and no homology has been found with the sequence of other iron storage or transport proteins such as ferritin or transferrin.
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PMID:Bovine heart microsomes contain an Mr = 66,000 non-heme iron protein which stimulates NADPH oxidation. 193 64

We developed a method for measuring the content of NADPH-ferrihemoprotein reductase in sections of liver. First, reductase in sections of rat liver was detected with the indirect immunoperoxidase reaction. Subsequently, specific absorbances were measured in the stained sections by microphotometry. Then, the resulting specific absorbances were converted into the reductase content in the sections using an apparent extinction coefficient obtained from a nitrocellulose binding assay. The average of the reductase content in hepatocytes in periportal, intermediate, and perivenous zones thus measured was consistent with the value in liver homogenates estimated by enzyme-linked immunosorbent assay. Therefore, the present method gave accurate measurement of the reductase content in the sections. Perivenous hepatocytes contained 1.5 times as much reductase (1.15 nmol/g liver, mean for five animals) as that in periportal hepatocytes (0.74 nmol/g liver). The reductase content in hepatocytes in the intermediate zone (0.93 nmol/g liver) was intermediate between values of the periportal and perivenous hepatocytes.
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PMID:Measurement of NADPH-ferrihemoprotein reductase content in sections of liver. 194 Mar 18

Deposition of inhaled particulates onto the respiratory mucosa is relatively great in that portion of the nasal cavity unprotected by ciliated, goblet, or keratinized superficial cells. The cytochrome P-450 system is an important enzyme system involved in the biotransformation of xenobiotics into metabolites that are more readily absorbed. To examine the transitional region caudal to the nasal vestibule, nasal tissues of hamster and rat were prepared for immunocytochemistry. Blocks of tissue representing four levels along the long axis of the nasal cavity were examined. Paraffin sections were processed through the avidin-biotin peroxidase procedure, with diaminobenzidine tetrahydrochloride as the chromagen. Enzyme localization was accomplished through the use of antibodies for three rabbit cytochrome P-450 isozymes; 2, 5, and 6 (subfamilies IIB, IVB, and IA, respectively); and for rabbit NADPH-cytochrome P-450 reductase. Enzyme distribution was similar in both hamster and rat nasal tissues except in cells of striated and intercalated ducts of nasal glands and in cells of the nasolacrimal duct where immunoreactivity was greater in the hamster. Immunoreactivity for reductase and isozyme 2 was intense in nonciliated cells lining the nonolfactory epithelium, in sustentacular cells of the olfactory epithelium, and in acinar cells of olfactory glands. Distribution of reaction products to isozyme 5 and 6 were similar to but not so intense as those of reductase and isozyme 2. Reaction products for reductase and isozyme 2 occurred generally in the same cellular and intracellular regions with the following exceptions: isozyme 2 was more concentrated in cells of striated ducts and of the nasolacrimal duct, and reductase was more abundant in intercalated ducts of nasal glands.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Distribution of cytochrome P-450 monoxygenase enzymes in the nasal mucosa of hamster and rat. 204 56

The level of quinone oxidoreductases (microsomal and cytosolic DT-diaphorase, NADPH-cytochrome P450 reductase and NADH-cytochrome b5 reductase), superoxide dismutase and glutathione-related enzymatic activities in diethylstilbestrol (DES)-induced carcinogenesis in kidney from Syrian golden hamsters are presented. Animals that exhibited two different stages of DES-induced carcinogenesis in kidney--pre- and neoplastic lesions and tumorous lesions (after 6 and 8 months of continuous exposure to DES respectively)--were studied in comparison to kidneys from control animals. A dramatic decrease in microsomal and cytosolic DT-diaphorase activities (13.6 and 37.8% of controls), as well as in glutathione disulphide reductase (39.5%), and less marked in superoxide dismutase (45.6%), NADH cytochrome b5 reductase (61.9%) glutathione transferase (GST) towards 1-chloro-2,4-dinitrobenzene (CDNB) (66.2%) and glutathione peroxidase (GSH-Px) (80%) activities, were observed in kidneys with pre- and neoplastic lesions. NADPH-cytochrome P450 reductase and GST activity towards 4-hydroxy-2,3-trans-nonenal (4-HNE) showed no statistically significant variation at this stage of carcinogenesis. In kidney from animals with tumorous lesions, all the enzymatic activities mentioned above decreased, except for superoxide dismutase, which was increased to 186% of the control activity. GST activity towards 4-HNE again showed no statistically significant variation. These results suggest that if one-electron reduction of diethylstilbestrol-4',4''-quinone (DESQ) occurs, it may play a very important role in the development of DES carcinogenesis (pre- and neoplastic lesions), since at this stage of carcinogenesis the primary defense mechanisms against the oxygen free radicals generated in this way, i.e. SOD activity, is reduced to less than a half of control values. Both cytosolic and microsomal DT-diaphorase activities are unable at this stage of carcinogenesis to promote effectively the two-electron reduction of DESQ, which would avoid the initial formation of superoxide anion. The consequences of these decreases may be an increased steady-state concentration of superoxide anion and hydrogen peroxide, which in the presence of iron might lead to lipid peroxidation. GST activity towards 4-HNE could be responsible for the possible higher steady-state concentration of this lipid peroxidation product during DES treatment. The induction of DT-diaphorase and its protective role in the prevention of the development of pre- and neoplastic lesions in kidney from Syrian golden hamster during DES treatment is also discussed.
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PMID:The levels of quinone reductases, superoxide dismutase and glutathione-related enzymatic activities in diethylstilbestrol-induced carcinogenesis in the kidney of male Syrian golden hamsters. 211 5

1. The t-butylquinone metabolite of BHA was shown to redox cycle with NADPH-cytochrome P-450 reductase leading to enhanced NADPH-oxidase activity for both the purified and liver microsome-bound flavoprotein. Likewise, addition of t-butylquinone (20-100 microM) strikingly inhibited electron transfer from the flavoprotein reductase to cytochrome P-450 of liver microsomes from phenobarbital-treated rats. 2. When the effect of t-butylquinone on metabolism of biphenyl was evaluated with liver microsomal fractions or isolated hepatocytes, t-butylquinone was less effective as an inhibitor then BHA alone or vitamin K3 (menadione). Addition of dicoumarol had little or no effect on the inhibitory potency of either t-butylquinone or vitamin K3 in isolated hepatocytes. 3. t-Butylquinone was not an effective reductant for exogenous oxidants, such as cytochrome c, in the presence of purified, cytosolic NAD(P)H-quinone oxidoreductase (DT-diaphorase). This property is most probably due to the lower rate of reoxidation of t-butylquinone by molecular oxygen, relative to vitamin K3 (menadione).
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PMID:The effect of the tert-butylquinone metabolite of butylated hydroxyanisole on cytochrome P-450 monooxygenase activity. 212 6


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