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)

Ferredoxin, ferredoxin-NADP+ reductase and plastocyanin extracted from spinach chloroplasts were determined by quantitative immunoelectrophoresis in an antiserum-containing gel. The advantage of the method is its high sensitivity and specificity so that crude extracts can be directly analysed. It requires, however, purified electron carriers and the corresponding monospecific antibodies. The ratios of ferredoxin to reductase to plastocyanin approximated 5:3:4, respectively, per cytochrome f or P700 in spinach chloroplasts.
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PMID:Quantitative determination of ferredoxin, ferredoxin-NADP+ reductase and plastocyanin in spinach chloroplasts. 62 5

Ferredoxin immobilized on Sepharose 4B was prepared by reaction of CNBr-Sepharose 4B with spinach ferredoxin. The ferredoxin-Sepharose 4B conjugated ferredoxin-NADP+ reductase (NADPH: ferredoxin oxidoreductase, [EC 1.6.7.1]) in dilute buffer solution and released it in high salt concentrations. A novel method of preparation for the reductase was established by a combination of affinity adsorption on the ferredoxin-Sepharose 4B column with usual purification procedures. It was found using the new method, that there are two forms of ferredoxin-NADP+ reductase, FNR I and FNR II, in spinach. Comparative studies of the two components suggest that FNR I may be a dimer of FNR II.
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PMID:Ferredoxin-Sepharose 4B as a tool for the purification of ferredoxin-NADP+ reductase. 63 27

Purified antisera against ferredoxin, ferredoxin-NADP+ reductase and plastocyanin agglutinated osmotically shocked and washed spinach chloroplasts, prepared according to standard procedures. The monomeric antibody (immunoglobulin G fraction) of the reductase antiserum agglutinated chloroplasts specifically and directly, indicating that protruding structures (for example, the coupling factor) do not act as steric hindrances as has been suggested. With ferredoxin antiserum, the presence of a pentameric antibody (immunoglobulin M fraction) was obligatory to observe a positive agglutination reaction. Immunoglobulin G only inhibited ferredoxin-dependent reactions, like NADP+-photoreduction, but did not cause agglutination. Ferredoxin seems to be located in depressions of the membrane, possibly caused by a partial release of this protein in shocked chloroplasts. Similar results were obtained with purified immunoglobulins from a plastocyanin antiserum. Again the immunoglobulin G fraction inhibited electron transport reactions catalyzed by plastocyanin, whereas immunoglobulin M showed a positive agglutination, but had no influence on electron transport. It is concluded that ferredoxin, ferredoxin-NADP+ reductase and plastocyanin are peripheral electron transport components, located at the outer thylakoid membrane.
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PMID:Reactions of antibodies against ferredoxin, ferredoxin-NADP+ reductase and plastocyanin with spinach chloroplasts. 64 22

Isolated thylakoid membranes are damaged during freezing in dilute salt solutions, as shown by the inactivation of photochemical thylakoid reactions. After freezing, a number of membrane proteins were found in the particle-free supernatant. Up to 5% of the total membrane protein was solubilized by freezing, and the pattern of released proteins as seen in sodium dodecyl sulfate gel electrophoretograms was influenced by the nature of the solutes present. Membranes protected by sucrose did not release much protein during freezing. Concentrated salt solutions caused protein release also in the absence of freezing. Among the proteins released were ferredoxin--NADP+ reductase, plastocyanin and coupling factor CF1. Subunits of CF1 were found in different proportions in the supernatants of thylakoid suspensions after freezing in the presence of different salts. Cyclic photophosphorylation was largely inactivated before significant protein release could be detected. It is suggested that protein release is the final consequence of the nonspecific suppression of intramembrane ionic interactions by the high ionic strength created in the vicinity of the membranes by the accumulation of salts during slow freezing. Salt effects on water structure and alterations of nonpolar membrane interactions by the incorporation of (protonated) lipophilic anions from organic salts into the membrane phase during freezing may also be involved.
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PMID:Loss of function of biomembranes and solubilization of membrane proteins during freezing. 68 24

NADPH-ferredoxin reductase (NADPH:ferredoxin oxidoreductase, EC 1.6.7.1) has been identified in rat liver mitochondria and purified to homogeneity as judged by sodium dodecyl sulfate (SDS) gel electrophoresis. The protein was detected by its ability to reconstitute NADPH-cytochrome c reductase in the presence of adrenal ferredoxin. The purified protein had properties very similar to adrenal NADPH-ferredoxin reductase. The molecular weight was 52 000, as estimated by gel filtration. On SDS-polyacrylamide gels, mobility was identical to that of adrenal NADPH-ferredoxin reductase (Mr = 52 000). The enzyme exhibited a typical oxidized flavoprotein absorbance spectrum with maxima at 269, 377 and 450 nm and gave an absorbance ratio A450nm/A269nm of 0.138. The fluorescence excitation spectrum was identical to that of FAD. In the presence of NADPH and a ferredoxin, the reductase was found to be active in a reconstituted cytochrome P-450-dependent steroid 26-hydroxylase, which was recently isolated from rat liver mitochondria (Pedersen, J.I. (1978) FEBS Lett. 85, 35-39).
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PMID:Purification of NADPH-ferredoxin reductase from rat liver mitochondria. 68 32

The molecular weight of spinach ferredoxin-NADP reductase [EC 1.6.99.4] was estimated to be 33,100 by the sedimentation equilibrium method. On the basis of this molecular weight, the amino acid composition of the reductase was determined. The reactivity of ferredoxin toward p-chloromercuribenzoate was investigated. By measuring the time course of the reaction, 1 mol of ferredoxin was found to react with about 8 mol of p-chloromercuribenzoate in 10 min. Under low ionic strength conditions (1 mM NaCl), the second-order rate constants of this reaction determined spectrophotometrically at 420 and 250 nm were 3,640 and 3,690 M-1.S-1, respectively; under high ionic strength conditions (100 mM NaCl), these rate constants were 1,360 and 1,270 M-1.S-1, respectively. In the presence of the reductase, the rate constants under low and high ionic strength conditions were 54 and 1,040 M-1.S-1, respectively. By investigation of the solvent perturbation effects on the aromatic amino acid residues with 20% ethylene glycol, it was found that ferredoxin, ferredoxin-NADP reductase, and the complex between these proteins had 2.8, 6.3, and 3.8 mol of exposed tyrosyl residues per mol of protein, respectively. It therefore seems likely that about 5 tyrosyl residues may exist in the neighborhood of the binding site of the complex of these proteins.
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PMID:Studies on the ferredoxin-ferredoxin-NADP reductase complex: kinetic and solvent perturbation studies on the location of sulfhydryl and aromatic amino acid residues. 72 1

A variety of nitroaromatic compounds, including 2,4,6-trinitrotoluene (TNT), were reduced by hydrogen in the presence of enzyme preparations from Veillonella alkalescens. Consistent with the proposed reduction pathway, R-NO2 H2 leads to R-NO H2 leads to R-NHOH H2 leads to R-NH2, 3 mol of H2 was utilized per mol of nitro group. The rates of reduction of 40 mono-, di-, and trinitroaromatic compounds by V. alkalescens extract were determined. The reactivity of the nitro groups depended on other substituents and on the position of the nitro groups relative to these substituents. In the case of the nitrotoluenes, the para-nitro group was the most readily reduced, the 4-nitro position of 2,4-dinitrotulene being reduced first. The pattern of reduction of TNT (disappearance of TNT and reduction products formed) depended on the type of preparation (cell-free extract, resting cells, or growing culture), on the species, and on the atmosphere (air or H2). The "nitro-reductase" activity of V. alkalescens extracts was associated with protein fractions, one having some ferredoxin-like properties and the other possessing hydrogenase activity. Efforts to eliminate hydrogenase from the reaction have thus far been unsuccessful. The question of whether ferredoxin acts as a nonspecific reductase for nitroaromatic compounds remains unresolved.
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PMID:Microbial transformation of 2,4,6-trinitrotoluene and other nitroaromatic compounds. 77 50

Comparison of various chloroplast-type ferredoxin sequences, chemical and enzymic modifications, reconstitution experiments, and fluorescence measurement of chloroplast-type ferredoxins have led to the following conclusions. 1. Tyrosine, histidine, and tryptophan residues are not directly involved in the oxidation-reduction mechanism of ferredoxins. The four indispensible cysteine residues in spinach ferredoxin which constitutes a part of the iron-sulfur cluster are located at residues 39, 44. 47 and 77. Two out of six cysteine residues in Spirulina ferredoxin could be easily modified with vinylpyridine without the loss of reconstitutive ability i.e. the apoferredoxin could be converted to the holoform by the addition of iron and sulfide. 2. Spinach ferredoxin was digested with carboxypeptidase A and the terminal alanine could be removed without loss of the spectral properties of native ferredoxin. However, the removal of the terminal three residues gave rise to the loss of reconstitutive ability. 3. The amino groups of spinach ferredoxin were modified by acetic anhydride and four residues were acetylated. The acetylated preparation of ferredoxin had an unique spectrum. Upon the addition of high concentration of ions the spectrum of this derivative resembled the spectrum of native ferredoxin. Acetylferredoxin did not combine with ferredoxin-NADP reductase, but upon the addition of moderate concentrations of cations, it did bind to this enzyme.
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PMID:Structure and function of chloroplast-type ferredoxins. 78 73

1. A reaction center from chloroplasts was purified by means of detergent treatment, differential centrifugation, column chromatography, and sucrose gradient. 2. The reaction center is active in NADP photoreduction by ascorbate. Ferredoxin, ferredoxin-NADP-reductase, and plastocyanin were required for the reaction. 3. The preparation contains five classes of polypeptide chains with apparent molecular weights of 70,000, 25,000, 20,000, 18,000 and 16,000 as determined by gel electrophoresis in sodium dodecyl sulfate. 4. Treatment with 0.5% sodium dodecyl sulfate abolished the NADP photoreduction activity and released the low molecular weight subunits, which were removed by sucrose gradient centrifugation from the high molecular weight ones. The P700 signal is associated with the 70,000 molecular weight polypeptide. 5. Antibody, prepared against the active reaction center, inhibited NADP photoreduction catalyzed by the purified reaction center as well as by isolated chloroplasts. The antibody interacted on immunodiffusion plates with any subchloroplast preparation capable of NADP photoreduction. It also interacted with the purified 70,000 molecular weight polypeptide. 6. It is concluded that both the primary oxidation and the primary reduction in Photosystem I are associated with the 70,000 molecular weight polypeptide.
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PMID:Purification and properties of the photosystem I reaction center from chloroplasts. 80 81

Polylysine stimulates the activity of ferredoxin-NADP reductase. The stimulation is observed with three different catalytic activities of this enzyme. The stoichiometry of interaction of polylysine and enzyme is a function of the size of the polylysine molecule. Polylysine alters the absorption and fluorescence emission spectra of the enzyme with the same stoichiometry as that affecting catalytic activity. Steady state initial velocity kinetics indicates that polylysine is a noncompetitive hyperbolic activator of the enzyme and is able to prevent substrate inhibition by NADPH. In the absence of polylysine, the specific activity of the enzyme increases upon dilution, and this effect is magnified in the presence of polylysine. These results suggest that the soluble enzyme is an aggregate, and gel filtration measurements indicate a molecular weight of 85,000 for the purified enzyme, which appears to consist of two subunits. This confirms the observations of Fredricks and Gehl (FREDRICKS, W. W., AND GEHL, J. M. (1973) Fed. Proc. 32, 477). Indirect evidence is presented suggesting the enzyme is bound to a cationic region on the chloroplast membrane.
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PMID:Polycation interactions with spinach ferredoxin-nicotinamide adenine dinucleotide phosphate reductase. 80 71


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