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)

To determine if the interaction between ferredoxin and ferredoxin:NADP reductase is similar to the interaction between the purified proteins when the ferrodoxin:NADP reductase is membrane bound, the effect of pH, salt, and coupling state on the Km for ferredoxin in NADP reduction by chloroplast membranes has been examined. Increasing pH and salt concentrations as well as uncouplers all resulted in increases in the Km for ferredoxin. The pH and salt effects on the Km are similar to effects observed by others (C. Batie and H. Kamin (1981) J. Biol. Chem. 256, 7756-7763) on the dissociation constant for a complex between the two purified proteins, although the salt effect on the Km appears to be affected by the surface potential of the chloroplast membrane. These results suggest that the interaction between ferredoxin and the membrane-bound ferredoxin:NADP reductase is not greatly different from the interaction which has been characterized between the two purified proteins.
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PMID:Effect of pH, salt, and coupling state on the interaction of ferredoxin with the chloroplast membrane. 662 16

The chemical trimethylcyclohexanol (TMC) is closely related to menthol, the major component of a terpene preparation with known choleretic and cholelitholytic activity. Its effects on hepatic cholesterol synthesis and bile secretion were examined in the rat. In both acute and long-term dosing experiments TMC significantly inhibited hepatic S-3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase. TMC was a potent choleretic, with detectable effects on bile flow at low doses, which also reduced coupling of cholesterol secretion to bile salt secretion. Single large doses tended to lower biliary cholesterol output and caused significant reduction in cholesterol saturation index after biliary diversion for 1 h. TMC and its widely prescribed ester cyclandelate, which is rapidly degraded to TMC after ingestion, should be investigated further as potential cholelitholytic treatments in man.
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PMID:The effects of 3,5,5-trimethylcyclohexanol on hepatic cholesterol synthesis, bile flow and biliary lipid secretion in the rat. 670 80

Prostaglandin (PG) E2 and F2 alpha synthesis by isolated glomeruli and papillary homogenates prepared from control, salt-loaded, and salt-depleted rats was measured in vitro with and without added arachidonic acid using specific radioimmunoassays. Glomeruli from salt-depleted rats synthesized less PGE2 and more PGF2 alpha than glomeruli from control rats under both conditions. The effect of sodium restriction could be attributed to stimulation of glomerular 9-keto-PGE2 reductase activity unrelated to a change in the concentration of this enzyme. High salt diet had no effect on PG synthesis by glomeruli. Papillary homogenates prepared from salt-loaded rats synthesized more PGE2 than those from control rats both with and without added arachidonic acid. This finding suggests an effect of high salt diet at a stage further than phospholipid deacylation. Low salt diet had no effect on PG synthesis by papillary homogenates. The physiological control of PG synthesis in response to changes in the NaCl content of the diet is, therefore, different for the glomeruli and the papilla.
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PMID:Altered PGE2 and PGF2 alpha production by glomeruli and papilla of sodium-depleted and sodium-loaded rats. 679 33

The triazine dyes, Cibacron blue F3GA and Procion red HE3B inhibited diaphorase activity of ferredoxin-NADP+ reductase, in a competitive manner with respect to NADPH. The Ki values were 1.5 and 0.2 microM, respectively. Binding of the dyes to the flavoprotein, as measured by difference spectroscopy, indicated an apparent stoichiometry of 1 mol dye/mol reductase and was prevented by NADP+ or high ionic strength. Chemical modification of a lysine residue and a carboxyl group at the NADP(H) binding site of the enzyme prevented complex formation with Procion red. Procion red showed a higher affinity for ferredoxin-NADP+ reductase than Cibacron blue. The Kd values were 1.9 and 5 microM, respectively. Once covalently linked to a Sepharose matrix, the triazine compounds specifically bind the flavoprotein. The interaction is partially electrostatic and partially hydrophobic. The enzyme can be eluted by high concentrations of salt or low concentrations of the corresponding coenzyme. The use of this affinity column allows the rapid purification of ferredoxin-NADP+ oxidoreductase from spinach leaves with good yields.
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PMID:Interaction of ferredoxin-NADP+ oxidoreductase with triazine dyes. A rapid purification method by affinity chromatography. 682 90

In vitro regulation of the key enzyme of cholesterol synthesis, 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.34) by compactin, a competitive inhibitor of the enzyme, and mevalonate was studied in rabbit ileum organ culture. Addition of compactin suppressed ileum homogenate reductase activity by over 80% at concentrations up to 0.5 microgram/ml. In contrast, compactin at the same concentrations added to the culture medium induced reductase activity up to 240% of controls. This increase was blocked by cycloheximide and mevalonolactone at 10 mM, but not by mevalonate (salt form) and cholesterol. Similarly, in contrast to ionized mevalonate, mevalonolactone significantly suppressed reductase activity of cultured intestine at 1 and 10 mM by 23 and 62%, respectively. A minor effect was also observed with preformed enzyme in fresh mucosal homogenate. When endogenous cholesterol synthesis was blocked by compactin, mucosal alkaline phosphatase activity decreased progressively, whereas medium activity from desquamated cells did not change. This distribution of the villous cell marker enzyme is characteristic of a decrease in crypt cell renewal and/or villous cell differentiation. This effect of compactin was also reversible with mevalonolactone. The reductase enzyme induced by compactin was probably latent intracellularly, since tissue cholesterol contents dropped sharply after blockade of endogenous sterol synthesis.
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PMID:Regulation of 3-hydroxy-3-methylglutaryl-CoA reductase by endogenous sterol synthesis in cultured intestinal mucosa. 722 1

The interaction between spinach ferredoxin and ferredoxin:NADP+ reductase was studied by varying pH and oxidation-reduction state. The Kd of the oxidized ferredoxin . ferredoxin:NADP+ reductase complex increases with increasing pH in the range from pH 6 to pH 8; the Kd is pH-independent above pH 9. These data are interpreted as showing 1 proton binding/complex at neutral pH. The extent of association of the complex was also varied by manipulation of salt concentration, was also varied by manipulation of salt concentration, and of concentration of the individual proteins. Increased association accompanied a negative shift in potential of ferredoxin relative to that of ferredoxin: NADP+ reductase. Oxidation-reduction titrations showed that the oxidation-reduction potential of ferredoxin is reduced to above -510 mV when in complex with ferredoxin:NADP+ reductase, a change of about -90 mV; the potential of ferredoxin:NADP+ reductase is changed little (no more than +20 mV). Conversely, these data also showed that the oxidation-reduction state of ferredoxin strongly affected its association with the flavoprotein, increasing the Kd at least 30-fold on reduction of ferredoxin.
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PMID:The relation of pH and oxidation-reduction potential to the association state of the ferredoxin . ferredoxin:NADP+ reductase complex. 726 26

Circular dichroic spectra of NADPH-adrenodoxin reductase, adrenodoxin and the complex between oxidized adrenodoxin reductase and oxidized adrenodoxin were studied. A 1 : 1 complex formation between adrenodoxin reductase and adrenodoxin resulted in the appearance of a distinct difference CD spectrum, which was obtained by subtraction of the sum of their CD spectra from the CD spectrum of the mixture of the two proteins. The difference CD spectrum showed a broad trough between 500 and 600 nm and CD extrema at 452, 383, and 350 nm. This spectrum may reflect a change in the environment of either or both of the protein chromophores. By applying the curve-fitting method to analyze the ellipticity change at 452 nm of the difference CD spectrum obtained on titration of a fixed amount of adrenodoxin reductase with various amounts of adrenodoxin, we directly obtained a value of 4.56 x 10(-7) M (S.D. 9.58 x 10(-8) M) as the dissociation constant of the oxidized complex. We also studied the change of the difference ellipticity induced by the addition of salt and obtained dissociation constants for the oxidized complex at various concentrations of NaCl. These values were larger than those obtained previously by kinetic methods, measurements of NADPH-cytochrome c reductase and NADPH-DCIP reductase activities. Further, we examined the relationship between the change of these activities on the addition of salt and the complex concentration calculated using the dissociation constant obtained in this study and found that the change of these activities could not be attributed simply to dissociation of the oxidized complex.
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PMID:Circular dichroic studies on the interaction between reduced nicotinamide adenine dinucleotide phosphate-adrenodoxin reductase and adrenodoxin. 733 14

Site-directed mutagenesis of the acidic clusters 207Asp-Asp-Asp209 and 213Glu-Glu-Asp215 of NADPH-cytochrome P450 oxidoreductase demonstrates that both cytochrome c and cytochrome P450 interact with this region; however, the sites and mechanisms of interaction of the two substrates are clearly distinct. Substitutions in the first acidic cluster did not affect cytochrome c or ferricyanide reductase activity, but substitution of asparagine for aspartate at position 208 reduced cytochrome P450-dependent benzphetamine N-demethylase activity by 63% with no effect on KP450m or KNADPHm. Substitutions in the second acidic cluster affected cytochrome c reduction but not benzphetamine N-demethylase or ferricyanide reductase activity. The E213Q enzyme exhibited a 59% reduction in cytochrome c reductase activity and a 47% reduction in KCyt cm under standard conditions (x0.27 M potassium phosphate, pH 7.7), as well as a decreased KCyt cm at every ionic strength and a shift of the salt dependence of cytochrome c reductase activity toward lower ionic strengths. The E214Q substitution did not affect cytochrome c reductase activity under standard conditions, but shifted the salt dependence of cytochrome c reductase activity toward higher ionic strengths. Measurements of the effect of ionic strength on steady-state kinetic properties indicated that increasing ionic strength destabilized the reductase-cytochrome c3+ ground state and reductase-cytochrome c transition state complexes for the wild-type, E213Q, and E214Q enzymes, suggesting the presence of electrostatic interactions involving Glu213 and Glu214 as well as additional residues outside this region. The ionic strength dependence of kcat/KCyt cm for the wild-type and E214Q enzymes is consistent with the presence of charge-pairing interactions in the transition state and removal of a weak ionic interaction in the reductase-cytochrome c transition-state complex by the E214Q substitution. The ionic strength dependence of the E213Q enzyme, however, is not consistent with a simple electrostatic model. Effects of ionic strength on kinetic properties of E213Q suggest that substitution of glutamine stabilizes the reductase-cytochrome c3+ ground-state complex, leading to a net increase in activation energy and decrease in kcat. Glu213 is also involved in a repulsive interaction with cytochrome c3+. Cytochrome c2+ Ki for the wild-type enzyme was 82.4 microM at 118 mM ionic strength and 10.8 microM at 749 mM ionic strength; similar values were observed for the E214Q enzyme. Cytochrome c Ki for the E213Q enzyme was 17.6 microM at 118 mM and 15.7 microM at 749 mM ionic strength, consistent with removal of an electrostatic repulsion between the reductase and cytochrome c2+.
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PMID:Role of acidic residues in the interaction of NADPH-cytochrome P450 oxidoreductase with cytochrome P450 and cytochrome c. 749 4

Quinones which are produced during the mineralization of lignin and xenobiotics by the white rot fungus Phanerochaete chrysosporium were reduced by a plasma membrane redox system of the fungus. Both intracellular enzymes and the plasma membrane redox system were able to reduce 1,4-benzoquinone. However, no quinone reductase activity was observed with the extracellular culture fluid. The intracellular reductase activity had a pH optimum between 6.0 and 7.0 and a Km of 150 microM. Reduction of 1,4-benzoquinone by the plasma membrane redox system had a pH optimum between 7.5 and 8.5 and exhibited saturation kinetics (Km = 11 microM, Vmax = 16 nmol/min/mg mycelia dry weight). Ferricyanide totally inhibited the quinone reduction until the ferricyanide was completely reduced by the membrane. Radicals (chlorpromazine and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)) that can be generated by the lignin peroxidases were also reduced by the plasma membrane redox system. Reduction of the ABTS cation radical also totally inhibited quinone reduction until the radical was completely reduced. Finally, quinone reduction rates were identical after the reduction of ferricyanide, ABTS cation radical, or quinone, suggesting that the plasma membrane redox system may actually protect the fungus from oxidative damage from free radicals generated by the lignin degrading system.
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PMID:Reduction of quinones and radicals by a plasma membrane redox system of Phanerochaete chrysosporium. 757 79

The refined crystal structures of the recombinant cytochrome b reductase fragment of corn (Zea mays) nitrate reductase, its ADP complex and the active-site mutant Cys242Ser are reported here. The native structure has been refined at 2.5 A resolution to a crystallographic R-factor of 18.7% with root-mean-square (r.m.s) deviations from standard bond lengths and angles of 0.013 A and 2.0 degrees. The diffraction pattern of the crystals is highly anisotropic and correction of this effect lowered the crystallographic R-factor by 5% during the refinement. The structure of the enzyme co-crystallized with ADP has been solved at 2.7 A resolution and refined to an R-factor of 18.6% with r.m.s. deviations from standard bond lengths and angles of 0.014 A and 2.1 degrees. It revealed the binding site of the ADP moiety of the NADH cofactor, which is the electron donor for nitrate reduction. Based on this structure, a model of NADH at the active site of the enzyme was built and the implications for electron transfer from NADH to the flavin cofactor are discussed. The crystal structure of an active-site mutant enzyme, Cys242Ser, has been solved by difference Fourier synthesis and refined to an R-factor of 19.0% to 3.0 A resolution with standard deviations of bond lengths and angles of 0.017 A and 2.5 degrees. This structure analysis suggests that the observed decrease in catalytic activity of this mutant might be due to misalignment of the nicotinamide ring in its binding site. A model of the heme-containing domain of nitrate reductase has been built based on the X-ray structure of bovine cytochrome b5 and has been docked with the cytochrome b reductase fragment of nitrate reductase. The model of the complex contains six salt-bridges at the domain-domain interface and a hydrophobic core. In this model, His48, an invariant residue in the cytochrome b reductase family, forms an interaction with the propionic acid group of the D-ring of the heme cofactor. This group is in contact with the C-8 methyl group of the flavin ring. Residues that might influence the redox potential of the flavin cofactor are proposed and their possible role in electron transfer is discussed.
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PMID:Structural studies on corn nitrate reductase: refined structure of the cytochrome b reductase fragment at 2.5 A, its ADP complex and an active-site mutant and modeling of the cytochrome b domain. 776 Mar 34


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