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)

1. Chymotrypsin treatment of chloroplast membranes inactivates Photosystem II. The inactivation is higher when the activity is measured under low intensity actinic light, suggesting that primary photochemistry is preferentially inactivated. 2. Membrane stacking induced by Mg2+ protects Photosystem II against chymotrypsin inactivation. When the membranes are irreversible unstacked by brief treatment with trypsin, Mg2+ protection against chymotrypsin inactivation of Photosystem II is abolished. 3. The kinetics of inactivation by chymotrypsin of Photosystem II indicates that membrane stacking slows down, but does not prevent, the access of chymotrypsin to Photosystem II, which is mostly located within the partition zones. 4. It is concluded that a partition gap exists between stacked membranes of about 45 A, the size of the chymotrypsin molecule. 5. The kinetics of inhibition of the chloroplast flavoprotein, ferredoxin-NADP reductase, bt its specific antibody is not affected by membrane stacking. This indicates that this enzyme is located outside the partition zones.
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PMID:Partition zone penetration by chymotrypsin, and the localization of the chloroplast flavoprotein and photosystem II. 44 96

Reaction of spinach leaves ferredoxin-NADP+ reductase (NADPH:ferredoxin oxidoreductase, EC 1.6.7.1) with alpha-dicarbonyl compounds results in a biphasic loss of activity. The rapid phase yields modified enzyme with about 30% of the original activity, but no change in the Km for NADPH. Only partial protection against inactivation is provided by NADP+, NADPH and their analogs, whereas ferredoxin affords complete protection. The reductase inactivated to 30% of original activity shows a loss of about two arginyl residues, whereas only one residue is lost in the NADP+-protected enzymes. The data suggest that the integrity of at least two arginyl residues are requested for maximal activity of ferredoxin-NADP+ reductase: one residue being located near the NADP+-binding site, the other presumably situated in the ferredoxin-binding domain.
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PMID:Modification of arginyl residues in ferredoxin-NADP+ reductase from spinach leaves. 44 39

The amounts of ferredoxin, plastocyanin, ferredoxin-NADP-reductase were determined by electrophoresis and differential spectroscopy. The cytochrome levels in the chloroplasts of non-photosynthesizing mutants Chlamydomonas reinhardii were determined both in active and inactive photosystems. It was shown that the loss of PS-1 activity did not affect the amount and activity of the electron carriers. The disturbances of the donor side of PS-2 in the mutants were accompanied by a loss of the reaction center activity and by a decrease of cytochrome b599. The amounts of other protein components in the mutants with inactive PS-2 remained unchanged. The disturbances in the cytochrome c553 content presumably blocked the electron transfer between the photosystems but did not affect the activity of the reaction centers of PS and the levels of other carriers of the chloroplast electron transport chain.
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PMID:[Protein carriers of the electron transport chain of non-photosynthesizing mutants of Chlamydomonas reinhardii]. 49 78

The ultrastructural localization of glucose-6-phosphate dehydrogenase (NADP-linked) has been attempted in steroid-secreting cells. Rat adrenocortical cells and newt testicular glandular cells were fixed in an ice-cold mixture of 1% methanol-free formaldehyde and 0.25% glutaraldehyde. Potassium ferricyanide was used as the final electron acceptor. After incubation, the final copper ferrocyanide precipitate is exclusively observed in the hyaloplasm of these cells, provided that an electron carrier (1.0 mM PMS) has been added to the medium in order to by-pass the tissue "diaphorase" (NADPH-ferricyanide reductase) reaction. No precipitate appears in the absence of glucose-6-phosphate (substrate). Incubation in a medium devoid of PMS results in an exclusively mitochondrial reaction; the latter is that of the "diaphorase", which in these cells is mitochondrial. These results prove the importance of utilizing exogenous electron carriers (such as PMS) in coenzyme-linked dehydrogenase cytochemistry. Although polyvinyl alcohol was included in the washing and incubation media, in order to increase their viscosity, problems still exist concerning ultracytochemical localization of this "soluble" enzyme; these problems are discussed in the paper.
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PMID:Ultrastructural demonstration of glucose-6-phosphate dehydrogenase activity in steroid-secreting cells. 50 Apr 6

The effects of a wide variety of oxygenated sterols upon sterol biosynthesis and hydroxymethylglutaryl-CoA reductase (mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34) activity in a wild-type clone and in a 25-hydroxycholesterol-resistant clone of Chinese hamster lung (Dede) cells are described. Derivatives of cholesterol which were oxygenated in the 6, 7 or 15 positions of the sterol nucleus or in the 20, 22, 24 or 25 positions of the sterol side chain were shown to be potent inhibitors of sterol synthesis and reductase activity in the wild-type cells but none of these substitutions had any effect on the 25-hydroxycholesterol-resistant A2 clone. A 32-hydroxylated derivative of lanosterol also suppressed sterol synthesis and reductase activity in wild-type cells but had no significant effect upon the A2 line. It was also appraent that a complete sterol side chain was necessary for inhibitory activity. Studies of a wide range of inhibitory sterols indicated that there was a close correlation between their effects upon sterol synthesis and reductase activity and that their inhibitory action was specific for sterol biosynthesis since little effect was observed upon fatty acid or CO2 synthesis. Previous studies had shown that the uptake of 25-hydroxycholesterol by the resistant A2 line was unimpaired and the present results indicate that metabolism of this oxygenated sterol is also unaltered. These results, in conjunction with previous studies, suggest that the resistant A2 line is defective in feedback regulation of cholesterol synthesis and that all of the oxygenated sterols tested suppress the biosynthetic pathway through at least one common step.
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PMID:Effects of various oxygenated sterols on cellular sterol biosynthesis in Chinese hamster lung cells resistant to 25-hydroxycholesterol. 50 85

NADPH-cytochrome P-450 reductase was isolated from liver microsomes of phenobarbital-induced rats. The enzyme exhibits an apparent minimal molecular weight of 76,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and contains 1 molecule each of FMN and FAD. Trypsin treatment of the reductase yields an enzyme with an apparent minimal molecular weight of 69,000 which retains the ability to reduce cytochrome c but has no activity toward cytochrome P-450. Various spectrophotometric titrations were performed to examine the electron-accepting properties of the purified NADPH-cytochrome P-450 reductase and, in particular, to determine the oxidation state of the stable semiquinone form produced by air oxidation of NADPH-reduced enzyme. Titration of the air-stable semiquinone form of the reductase with ferricyanide indicated that 1 mol/2 mol of flavin was required for complete oxidation. Furthermore, a spectrum corresponding to that of the air-stable semiquinone form was produced by the addition of approximately 0.5 mol of reductant/2 mol of flavin when the oxidized enzyme was titrate with NADPH or dithionite under anaerobic conditions. The spectral changes which accompanied the overall reduction of oxidized enzyme to the reduced form with dithionite produced four sets of isosbestic points, and the spectrophotometric titration curve consisted of four approximately equal phases. In the titration with NADPH, no significant further reduction was observed after the addition of approximately 1.5 mol/2 mol of flavin. However, the enzyme was fully reduced by NADPH when an NAPH-generating system was used to prevent the accumulation of NADP. Our results establish that the air-stable semiquinone form is a 1-electron-reduced form, rather than a half-reduced (2-electron-reduced) form as maintained by others and are in agreement with earlier studies (Iyanagi, T., Makino, N., and Mason, H.S. (1974) Biochemistry 13, 1701-1710) with the purified trypsin-solubilized reductase. Accordingly, the air-stable species represents a form of the NADPH-cytochrome P-450 reductase in which one of the two flavins exists in the semiquinone state and the other in the oxidized state.
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PMID:Purified liver microsomal NADPH-cytochrome P-450 reductase. Spectral characterization of oxidation-reduction states. 63 95

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

In a detailed study focused on the methodological problems in dehydrogenase histochemistry [e.g., fixation, diffusion of enzymes and of reduced inermediates, conversion of NADPH and NADP to NADH and NAD, respectively, penetration of tetrazolium salt and formazan substantivity, 'nothing dehydrogenase' reaction, use of exogenous CoQ10 and of flavoprotein substitute (PMS)], the distribution and activity of succinate dehydrogenase, NAD(P)H-tetrazolium reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase (H and M types), and of L-glutamate dehydrogenase (E.C.1.4.1.2 and E.C.1.4.1.3) have been investigated in the rat cerebellum. It was evident from the study that reliable results could only be obtained if all the aforementioned factors had been considered. The image of actual concentration of SDH in the neuropil of the molecular layer could only be recorded by adding CoQ10, while other structures exhibited greater balance between SDH and endogenous mitochondrial CoQ. Contrary to previous studies, a reversed localization of the activity of G-6-PDH and LDH was noticed. The elements of molecular and Purkinje layers were rich in G-6-PDH, while the granular layer was nearly depleted. The actual level of LDH could only be recorded if NADH-tetrazolium reductase was bypassed with PMS. The H and M types of LDH coexisted in the three cortical layers, the H type being prevalent and the M type attaining its highest level in synaptic glomeruli followed by the structures of the molecular layer and the Purkinje cells. High activity of GDH was noticed in Bergmann glia followed by synaptic glomeruli, while most other structures showed weak to moderate activity. The two GDH types coexisted in all structures showing activity, except for Bergmann cells, which only showed presence of the E.C. 1.4.1.3 type. Furthermore, Bergmann glia was exceptional by showing no activity of SDH and LDH, but strong activity of G-6-PDH and NADPH-tetrazolium reductase. The granular cells were exceptional by showing weak or no activity of all enzymes in question.
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PMID:Methodological aspects of the histochemical localization and activity of some cerebellar dehydrogenases. 66 87

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

A lauric acid monooxygenase which catalyzes the formation of hydroxylaurate from lauric acid has been characterized in ageing tissues of Jerusalem artichoke (Helianthus tuberosus L.) tuber. Three reaction products have been identified from the mass fragmentation pattern of their methyltrimethylsilyl derivatives: 10-hydroxylauric acid, 9-hydroxylauric acid and 8-hydroxylauric acid. Enzyme activity is located on the microsomal fraction which also carries cytochrome P-450 and NADPH cytochrome-c reductase. The apparent Km of the enzyme for lauric acid is 0.97 micronM. Laurate monooxygenation is dependent upon O2 and inhibited by CO. The latter effect is light reversible. NADPH is the preferred electron donor although appreciable NADH-sustained activity was observed. NADPH cytochrome c reductase is involved in electron transfer as evidenced by the inhibitory effects of NADP+ and oxidized cytochrome c on laurate monooxygenation. Thus, the enzyme catalyzing laurate oxidation in Jerusalem artichoke tuber tissues appears to be a typical (cytochrome P-450)-linked monooxygenase.
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PMID:A microsomal (cytochrome P-450)-linked lauric-acid-monooxygenase from aged Jerusalem-artichoke-tuber tissues. 71 Apr 15


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