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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Location of electron transport chain components in chloroplast membranes of chlamydomonas reinhardi, y-1 was investigated by use of proteolytic digestion with soluble or insolubilized trypsin. Digestion of intact membrane vesicles with soluble trypsin inactivates the water-splitting system, the 3-(3,4-dichlorophenyl)-1,1-dimethylurea inhibition site of Photosystem II, the electron transport between the two photosystems as well as the ferredoxin NADP reductase. Reduction of NADP with artificial electron donors for Photosystem I could be restored, however, by addition of purified reductase to trypsin-digested membranes. Electron transfer activities of Photosystems I and II reaction centers were resistant to trypsin digestion either from outside or from within the thylakoids when active trypsin was trapped inside the membrane vesicles by sonication and digestion carried out in the presence of trypsin inhibitor added from outside. In the latter case, the water-splitting system was also found to be resistant to digestion. Polyacrylamide-bound insolubilized trypsin inactivated only the ferredoxin NADP reductase. Photosynthetically active membranes obtained at different stages of development showed a basically similar behavior toward trypsin.
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PMID:Trypsin-sensitive photosynthetic activities in chloroplast membranes from Chlamydomonas reinhardi, y-1. 0 Apr

NADH and NADPH-ferredoxin oxidoreductases have been studied in Clostridium acetobutylicum, Cl. tyrobutyricum and Cl. pasteurianum. The study of the distribution and regulation of these enzymatic activities in well-defined culture conditions, reveals that the essential function of NADPH-ferredoxin oxidoreductase is to produce NADPH, while NADH-ferredoxin oxidoreductase can, depending on cellular conditions, produce or oxidize NADH. When these Clostridia use glycolysis, regulation of the NADH-ferredoxin oxidoreductase by acetyl-CoA (obligatory activator of NADH-ferroxin reductase activity) and by NADH (competitive inhibitor of ferredoxin-NAD+ reductase activity) allow the enzymes to function correlatively with glyceraldehyde-3-phosphate dehydrogenase and thus control the levels of NAD+ and NADH in the cell. In Cl. tyrobutyricum and Cl. pasteurianum, the ferredoxin-NADP+ reductase activities are regulated by NAD+ and NADH in accordance with the intracellular concentrations of these coenzymes. In Cl. tyrobutyricum growing on pyruvate/acetate, NADH and NADPH-ferredoxin reductase activities cannot be detected; only the ferredoxin-NAD+ and ferredoxin-NADP+ reductase activities are found. In this Clostridium, regulation of the ferredoxin-NADP+ reductase activity is the same whether it is grown on glucose or pyruvate. Contrary to this, the ferredoxin-NAD+ reductase activity undergoes a drastic change, since NADH no longer controls the enzymatic activity. In this case regulation is no longer necessary, since glyceraldehyde-3-phosphate dehydrogenase does not function.
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PMID:Regulation of the NADH and NADPH-ferredoxin oxidoreductases in clostridia of the butyric group. 0 18

Although a sulfate-reducing pathway in Escherichia coli involving free sulfite and sulfide has been suggested, it is shown that, as in Chlorella, a pathway involving bound intermediates is also present. E. coli extracts contained a sulfotransferase that transferred the sulfonyl group from a nucleosidephosphosulfate to an acceptor to form an organic thiosulfate. This enzyme was specific for adenosine 3'-phosphate 5'-phosphosulfate, did not utilize adenine 5'-phosphosulfate, and transferred to a carrier molecule that was identical with thioredoxin in molecular weight and amino acid composition. In the absence of thioredoxin, only very low levels of the transfer of the sulfo group to thiols was observed. As in Chlorella, thiosulfonate reductase activity that reduced glutathione-S-SO3- to bound sulfide could be detected. In E. coli, this enzyme used reduced nicotinamide adenine dinucleotide phosphate and Mg2+, but did not require the addition of ferredoxin or ferredoxin nicotinamide adenine dinucleotide phosphate reductase. Although in Chlorella the thiosulfonate reductase appears to be a different enzyme from the sulfite reductase, the E. coli thiosulfonate reductase and sulfite reductase may be activities of the same enzyme.
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PMID:Sulfate-reducing pathway in Escherichia coli involving bound intermediates. 0 97

NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii was isolated and purified by ammonium sulfate fractionation, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration. This enzyme is an FAD-containing flavoprotein and has absorption maxima at 485 (shoulder0 452, 411, and 385 nm (the 411 nm band is due to cytochrome). The molecular weight of the enzyme as determined by gel filtration using Sephadex G-200 is 119,000. The enzyme catalyzes the reduction of NAD+ and NADP+ by photoreduced spinach ferredoxin or reduced benzyl viologen...
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PMID:Isolation and some properties of NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii. 0 30

Photosystem I fragments were prepared by digitonin treatment of spinach chloroplasts. The midpoint potential of cytochrome b6 in the fragments is close to 0V, showing a one electron transition. No cytochrome b559 was detectable, neither in difference absorption spectra nor in light-induced absorbance changes. In the absence of added cofactors only cytochrome b6 photoreduction can be observed. This photoreduction is stimulated by ferredoxin. Ferredoxin-NADP+ reductase appears not to be involved in cytochrome b6 reduction. Photooxidation of cytochrome b6 is dependent on plastocyanin addition and inhibited by DBMIB, a plastoquinone antagonist. Addition of plastocyanin restores cytochrome f photooxidation as well, reacting quite specifically in about equimolar concentrations to bound cytochrome f. The stimulation of cytochrome f oxidation is abolished by an antibody prepared against plastocyanin, indicating a surface location of plastocyanin in digitonin treated membranes. Biphasic kinetics of dark-reduction of cytochrome f by ascorbate indicate that part of this cytochrome f is relatively inaccessible in the membrane. After preillumination a monophasic reduction is observed and the slowly oxidized component is absent. Illumination in the presence of plastocyanin causes a fast and complete reduction of cytochrome f, suggesting equilibration of cytochrome f with added plastocyanin, residing in the membrane surface. It appears that actinic light causes conformation and/or structural changes in the membrane of these digitonin fragments, influencing cytochrome f asseccibility.
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PMID:Photoreactions of cytochrome b6 and cytochrome f in chloroplast photosystem I fragments. 0 29

The binding site of NADPH in NADPH-adrenodoxin reductase was examined using crystalline enzyme from bovine adrenocortical mitochondria by studies on the effects of photooxidation and chemical modifications of amino acid residues in the reductase. (1) Photoxication decreased the enzymatic activity of NADPH-adrenodoxin reductase. Photooxidation of the reductase was prevented by NADP+, adrenodoxin, or reduced glutathione, but not NAD+. Photoinactivation caused loss of a histidyl residue, but not of tyrosyl, tryptophanyl, cysteinyl, or methionyl residues of the reductase. It did not affect the circular dichroism spectrum of the reductase appreciably. (2) NADPH-adrenodoxin reductase activity was inhibited by diethyl pyrocarbonate and the inhibition was partially reversed by addition of hydroxylamine. The inhibition was prevented by NADP+, but not NAD+. (3) NADPH-adrenodoxin reductase activity was inhibited by 5,5'-dithiobis(2-nitrobenzoate) and the inhibition was reversed by reduced glutathione. It was also protected by NADP+, but not NAD+. The results indicate that a histidyl residue and a cysteinyl residue of NADPH-adrenodoxin reductase are essential for the binding of NADPH by the reductase.
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PMID:Properties of crystalline reduced nicotinamide adenine dinucleotide phosphate-adrenodoxin reductase from bovine adrenocortical mitochondria. II. Essential histidyl and cysteinyl residues at the NADPH binding site of NADPH-adrenodoxin reductase. 0 83

Dansyl chloride, at low molar ratio, inactivates ferredoxin-NADP reductase (NADPH:ferredoxin oxidoreductase, EC 1.6.7.1). The complete protection afforded either by NADP or NADPH suggests a direct involvement of the active site. Experiments with [Me-14C] dansyl chloride showed that about 1.5 residues per flavin were dansylated: by differential labelling experiments using NADP, it has been proved that enzyme inactivation is due to dansylation of one residue. The group modified has been identified as the epsilon-amino group of a lysine. The pH-inactivation profile indicates that this essential group has an apparent pKa of 8.7. The dansylated flavoprotein seems to maintain its native conformation; it shows a fluorescent chromophore with a peak at 335 nm. The modified enzyme has lost the capacity to form a complex with NADP, nevertheless it interacts normally with ferredoxin. It is concluded that the loss of catalytic activity which parallels the dansylation of a lysyl residue occurs because this residue is essential for the binding of the pyridine nucleotide substrate. Protection experiments with a series of coenzyme analogs further indicate that this lysyl residue interacts, most likely, with the 2'-phosphate moiety of NADP(H).
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PMID:A lysyl residue at the NADP binding site of ferredoxin-NADP reductase. 0 35

A factor of protein nature, containing pteridines and iron ions was isolated from pea leaves. The compound was shown capable of activating NADP reduction during chloroplasts illumination in the absence of ferredoxin. The compound was termed "NADP-reducing factor" (NRP). Freshly isolated NRF in combination with the protein possessing the NADP-reductase activity, reduces NADP in the dark. The factor accepts the electron from the reaction site of the first photosystem and activates hydrogen liberation in the systems, containing hydrogenase. A possibility of an existence of an additional site of NADP reduction in chloroplasts is discussed.
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PMID:[Participation of the iron-containing pterine-protein complex in NADP reduction and electron transport]. 1 45

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

Proton uptake by isolated chloroplasts during cyclic electron transport in the presence of ferredoxin and under NADP+ reduction from the ascorbate--TMPD donor pair under anaerobic conditions was studied. It was found that during cyclic transport the proton uptake is less intensive than under NADP+ reduction. In the presence of ATP the proton uptake is increased in the first case and is decreased in the second one. During cyclic transport in the presence of gramicidin D the proton uptake is completely suppressed and under NADP+ reduction is decreased down to 0,08--0,09 mk equiv H+ per mg of chlorophyll, irrespective of ferredoxin or NADP+ concentrations. The role of ferredoxin NADP+ reductase in a proton uptake by thylakoids is discussed.
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PMID:[Porton uptake by isolated chloroplasts during cyclic and non-cyclic electron transport catalyzed by photosystem I in the presence of ferredoxin]. 8 67


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