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)

The change in fluorescence emission at 520 nm after excitation at 365 nm was used to investigate the effect of pH and ionic strength on the dissociation of flavin cofactors from microsomal NADPH/cytochrome c (P-450) reductase. In the unmodified enzyme both the FAD and FMN moieties appeared to dissociate at a similar rate and followed first-order kinetics. The rate constant for the dissociation was increased by low pH and high ionic strength, particularly in the range pH 4.4-3.8 (0.02 M acetate buffer) where the rate constants increased 80-fold. Modification of the enzyme by treatment with p-chloromercuribenzoate enhanced the rate of flavin dissociation and, in the region of pH 4, resulted in a biphasic increase in fluorescence consistent with two simultaneous parallel first-order dissociations. It was concluded that p-chloromercuribenzoate treatment modified the protein so that the two flavin cofactors dissociated at different rates. Using the measured rate constants for the dissociations, and the known variation in fluorescence of flavin nucleotides with pH, an analogue computer simulation of the dissociation as well as a manual curve-fitting procedure showed that the biphasic response could be explained as a simultaneous rapid dissociation of FAD and a slower loss of FMN from the protein.
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PMID:The dissociation of flavin coenzymes from trypsin-solubilized NADPH/Cytochrome c (P-450) reductase of pig-liver microsomes. 1 69

The presence of NADH-cytochrome b5 reductase [EC 1.6.2.2] in microsomes from anaerobically grown yeast was confirmed by its isolation and purification. The purified preparation of the reductase showed an apparent molecular weight of 27,000 daltons. The reductase appeared to contain loosely-bound FAD as a prosthetic group. The reductase required NADH as a specific electron donor, and could reduce some redox dyes as well as cytochrom b5. The reductase, however, could not reduce cytochrome c. Michaelis constants of the reductase for NADH and calf liver cytochrome b5 were 6.3 and 1.5 micron M, respectively, and optimal pH for cytochrome b5 reduction was 5.6. Although some differences exist between the properties of NADH-cytochrome b5 reductase from yeast and from mammalia, the results indicate a functional similarity of the present enzyme to mammalian NADH-cytochrome b5 reductase in the microsomal electron-transport system.
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PMID:Studies on the microsomal electron-transport system of anaerobically grown yeast. IV. Purification and characterization of NADH-cytochrome b5 reductase. 1 30

A flavoprotein catalyzing the reduction of cytochrome c by NADPH was solubilized and purified from microsomes of yeast grown anaerobically. The cytochrome c reductase had an apparent molecular weight of 70,000 daltons and contained one mole each of FAD and FMN per mole of enzyme. The reductase could reduce some redox dyes as well as cytochrome c, but could not catalyze the reduction of cytochrome b5. The reductase preparation also catalyzed the oxidation of NADPH with molecular oxygen in the presence of a catalytic amount of 2-methyl-1,4-naphthoquinone (menadione). The Michaelis constants of the reductase for NADPH and cytochrome c were determined to be 32.4 and 3.4 micron M, respectively, and the optimal pH for cytochrome c reduction was 7.8 to 8.0. It was concluded that yeast NADPH-cytochrome c reductase is in many respects similar to the liver microsomal reductase which acts as an NADPH-cytochrome P-450 reductase [EC 1.6.2.4].
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PMID:Studies on the microsomal electron-transport system of anaerobically grown yeast. V. Purification and characterization of NADPH-cytochrome c reductase. 1 31

The method of purification up to homogenous states and properties of NADP-reductase of purple bacteria Thiocapsa roseopersicina, strain BBS, are described. The molecular weight of NADP-reductase is about 47 000; it is flavoprotein consisting of two subunits. Atebrim and chloromercury bensoate inhibit the activity of NADP-reductase (34% and 33--60%, respectively). The enzyme is specific to NADPH; it catalyzes menadion-reductase reaction, diaphorase reaction of benzyl viologen reduction, oxidation of reduced benzyl viologen in the presence of NADP, reduction of ferredoxin and cytochrome c in the presence of NADPH, but it is not capable to catalyze transhydrogenase reaction.
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PMID:[Purification and properties of NADP-reductase of phototropic bacteria Thiocapsa roseopersicina]. 2 Jan 66

Unlike Rhodospirillum rubrum, the highly purified preparations of NADP-reductase Thiocapsa roseopersicina are capable of reduction of cytochrome c though they do not catalyse diaphorase reaction in the presence of methyl viologen or benzyl viologen and NADH. T. roseopersicina reductase has more high temperature optimum (50-65 degrees) and more high thermal stability (65 degrees) and it is capable to catalyse diaphorase and menadione-reductase reactions under more high pH values (11.0-12.0) than NADP-reductase of R. rubrum. NADP-reductase of T. roseopersicina is more stable under storing than the enzyme from R. rubrum: the semi-inactivation period of the enzyme when storing in Ar or the air is about 10 and 4 days, respectively, and it takes about three days for R. rubrum.
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PMID:[Comparative study of NADP-reductase properties in two species of purple bacteria]. 2 Sep 91

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

Oxidative deformylation of 4-hydroxy[14C]methylene-5alpha-cholest-7-en-3-one and oxidative demethylation of [30,31-14C]4,4-dimethyl-5alpha-cholest-7-en-3beta-ol by rat liver microsomes have been compared with regard to the manner in which electrons are introduced from both NADH and NADPH. Evidence suggests that NADH and NADPH support oxidation of both substrates via separate routes of electron transfer. Thus, 10 micron cytochrome c will inhibit NADPH-supported oxidation to 40 to 50% of control activity leaving NADH-supported oxidation unaffected. Also, treatment of microsomes with subtilisin diminishes NADPH-supported oxidation to 10 to 30% of control activity for either substrate to 70 to 90% of control activity while NADH-supported oxidative activity is virtually unaffected. Studies on the oxidase activities and NADPH-cytochrome c reductase as well as NADH-ferricyanide reductase have shown marked differences in activity in the presence of inhibitors. Thus, 9 mM 2'-AMP inhibits NADPH-cytochrome c reductase to 10 to 20% of control activity while NADPH-supported oxidative demethyl ation and deformylation are essentially unchanged. Mersalyl at 15 to 25 nmol/mg of microsomal protein inhibits both reductases to 20 to 40% of control activity; oxidative demethylation is unaffected and oxidative deformylation stimulated slightly when NADPH is used. Finally, antibody to NADPH-cytochrome c reductase inhibits oxidase activity for either substrate to 70 to 90% of control activity while reductase activity is inhibited to 10 to 30% of control activity.
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PMID:Mixed function oxidases in sterol metabolism. Separate routes for electron transfer from NADH and NADPH. 3 69

A b-type cytochrome and NADH-ferricyanide (FC) reductase were solubilized from Ascaris muscle microsomes by detergents and purified by column chromatography. The purified b-type cytochrome displayed absorption bands at 560 (alpha-peak), 525 (beta-peak), and 424 nm (gamma-peak), with a marked shoulder at 555 nm in the reduced from, 415 nm (gamma-peak) in the oxidized form. This absorption spectrum was different from that of rat liver microsomal cytochrome b5. The molecular weight was estimated to be about 100,000 by SDS-polyacrylamide gel electrophoresis, and the absorption spectrum of alkaline pyridine ferrohemochrome suggested that the prosthetic group of this cytochrome is protoheme. The molecular weight of the purified NADH-FC reductase was estimated to be about 55,000 by SDS-polyacrylamide gel electrophoresis. The purified reductase required NADH as a specific electron donor. The reductase efficiently reduced some redox dyes with NADH, but the reduction of cytochrome c was much slower. The purified reductase, like the membrane-bound reductase, was not inhibited by thiol reagents.
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PMID:Biochemical studies on the muscle microsomes of Ascaris lumbricoides var. suum. II. Purification and characterization of b-type cytochrome and NADH-ferricyanide reductase from Ascaris muscle microsomes. 3 74

From previous work (Guiard, B., Groudinsky, O. and Lederer, F. (1974) Proc. Natl. Acad. Sci. U.S. 71, 2539-2543) it is now clear that the overall secondary and tertiary structure of cytochrome b2 core is very similar to that of cytochrome b5. We present here a direct comparison of circular dichroism spectra and low-temperature absorption spectra which bring further evidence about this structural similarity. Cytochrome b2 core reacts only sluggishly with cytochrome b5 reductase, showing a lack of correspondence with the reductase binding area in cytochrome b5. On the other hand, literature data indicate similar electron transfer rates between cytochrome c on one hand, cytochrome b5 and cytochrome b2 core on the other hand. A structural inspection of cytochrome b2 core suggests that the mouth of the heme crevice in the latter is the most likely region for interaction with cytochrome c, with perhaps ionic bonds slightly different from those proposed by Salemme (Salemme, F.R. (1976) J. Mol. Biol. 102, 563--568) for the cytochrome c-cytochrome b5 interaction. In view of this partial surface similarity, the lack of immunological cross-reactivity between the two hemoprotein cores is attributed to their close similarity with the cytochrome b5 of the antibody-producing rabbit.
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PMID:Surface differences and similarities in two homologous proteins. Cytochrome b5 and cytochrome b2 core. 10 Dec 51

NADPH-cytochrome c (P-450) reductase (EC 1.6.2.4) was purified to apparent homogeneity from microsomes of house flies, Musca domestica L. The purification procedure involves column chromatography on three different resins. The key step in the purification scheme is the chromatography of the enzyme mixture on an affinity column of agarose-hexane-nicotinamide adenine dinucleotide phosphate. The enzyme has an estimated molecular weight of 83,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and contains 1 mol each of FAD and FMN per mol of enzyme. The enzyme exhibited a Bi Bi ping-pong kinetic mechanism with NADPH and cytochrome c. The Vmax and Km for cytochrome c were 42.3 mumol min-1 mg-1 and 12.7 muM, respectively. Turnover numbers based on micromoles of enzyme were 2,600 min-1. NADP+ and 2'-AMP both inhibited the reductases with apparent Ki values of 6.9 and 187 muM, respectively. These preparations of NADPH-cytochrome c reductase were found to reduce purified house fly cytochrome P-450 in the presence of NADPH.
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PMID:Preparation of homogenous NADPH cytochrome c (P-450) reductase from house flies using affinity chromatography techniques. 10 96


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