Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

X-band electron-paramagnetic-resonance spectroscopy at 4.2--77K combined with measurements of oxidation-reduction potential was used to identify iron--sulphur centres in Arum maculatum (cuckoo-pint) mitochondria. In the oxidized state a signal with a derivative maximum at g = 2.02 was assigned to succinate dehydrogenase centre S-3. Unreduced particles showed additional signals at g = 2.04 and 1.98 (at 9.2 GHz), which may be due to a spin-spin interaction. In the reduced state a prominent signal at g = 1.93 and 2.02 was resolved into at least three components that could be assigned to centres S-1 and S-2 of succinate dehydrogenase (midpoint potentials -7 and -240 mV respectively at pH 7.2) and a small amount of centre N-1b (e'o= -240 mV) of NADH-ubiquinone reductase. In addition, changes in line shape around -10 mV indicated the presence of a fourth component in this signal. The latter was more readily reduced by NADH than by succinate, suggesting that it might be associated with the external NADH dehydrogenase. The iron-sulphur centres of NADH-ubiquinone reductase were present in an unusually low concentration, indicating that the alternative, non-phosphorylating, NADH dehydrogenase containing a low number of iron-sulphur centres may be responsible for most of the high rate of oxidation of NADH.
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PMID:Iron-sulphur centres in mitochondria from Arum maculatum spadix with very high rates of cyanide-resistant respiration. 59 30

The effect of treating mitochondria with visible light above 400 nm on electron transport and coupled reactions was examined. The temporal sequence of changes was: stimulation of respiration coupled to ATP synthesis, a decline in ATP synthesis, inactivation of respiration, increased ATPase activity and, later, loss of the membrane potential. Loss of respiration was principally due to inactivation of dehydrogenases. Of the components of dehydrogenase systems, flavins and quinones were most susceptible to illumination, the iron-sulfur centers were remarkably resistant to being damaged. Succinate dehydrogenase was inactivated before choline and NADH dehydrogenase. Redox reactions of cytochromes and cytochrome c oxidase activity were unaffected. Inactivation was O2-dependent and prevented by anaerobiosis or the presence of substrates for the dehydrogenases. Light in the range 400-500 nm was most effective and the presence of free flavins greatly enhanced inactivation of all of the above mitochondrial activities. This suggests that visible light mediates a flavin-photosensitized reaction that initiates damage involving participation of an activated species of oxygen in the damage propagation.
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PMID:Damage to mitochondrial electron transport and energy coupling by visible light. 65 6

A membrane-bound NADH dehydrogenase, solubilized and partially purified from a marine bacterium Photobacterium phosphoreum, contains FAD as the prosthetic group, and is specific for NADH. Ferricyanide, various other redox dyes and cytochrome c can act as electron acceptors. The enzymatic activity when assayed with electron acceptors other than cytochrome c, is activated by monovalent cations (Na+ and K+) and deactivated by high concentrations of monovalent anions (SCN-, NO3-, and Cl-) but not by phosphate ions. The enzymatic reaction follows a ping-pong mechanism and kinetic analysis of the enzyme showed that the activation by monovalent cations is due to increase of affinity of the enzyme for substrates; Vm was not affected. The increase of affinity was 62- and 46-fold for NADH and 57- and 31-fold for 2,6-dichlorophenol indophenol in the presence of Na+ and K+, respectively. On the other hand, NADH-cytochrome c reductase activity of the enzyme was strongly inhibited by these cations.
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PMID:Properties and kinetics of salt activation of a membrane-bound NADH dehydrogenase from a marine bacterium Photobacterium phosphoreum. 72 93

Acholeplasma laidlawii A consists of pleomorphic cell clusters surrounded by a single membrane. When lysed, a cell gives rise to several membrane fragments which cannot be separated from each other by isopycnic sucrose gradient centrifugation. A heterogeneous lateral organization of the cell membranes was detected by countercurrent distribution of membrane fragments in a two-polymer aqueous phase system. It revealed that the membranes consist of at least two subpopulations with respect to surface properties. Changes in the fatty acid and cholesterol content of the membranes revealed that the resolution of different subpopulations was predominantly due to a critical ratio of monoglucosyldiglyceride to diglucosyldiglyceride. The heterogeneity of the membrane probably depends on lipid-lipid and lipid-protein steric interactions. Charged lipids, an apolar monoglucolipid and the ratio between lipids and proteins also affect membrane partition. The differences in the subpopulations were further reflected by different specific activities of NADH dehydrogenase, NADH oxidase and ATPase. These activities varied independently. Minor quantitative differences in the protein patterns of different subpopulations were apparent. The origin and the preservation of the membrane subpopulations are discussed in terms of lipid-lipid and lipid-protein interactions, their age and energy metabolism.
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PMID:Fractionation of membranes from Acholeplasma laidlawii A on the basis of their surface properties by partition in two-polymer aqueous phase systems. 76 Jul 84

The NADH dehydrogenase of the Escherichia coli respiratory chain has been identified by the following properties: (a) its location in membrane vesicles; (b) its inhibition by AMP in a fashion similar to that of the NADH oxidase; (c) its specificity for NADH, but not NADPH, with the same Km for NADH as that of the NADH oxidase; (d) its sensitivity when membrane-bound to inhibition by dicoumarol, rotenone, and 2-heptyl-4-hydroxyquinoline-N-oxide, which are also inhibitors for the NADH oxidase. The NADH-dehydrogenase of the cytosol fraction (assayed as NADH-dichlorphenolindophenol reductase activity) differs substantially from the membrane-bound activity both in substrate specificity and in the inhibitors of the reaction. The respiratory chain NADH dehydrogenase was extracted from isolated membrane vesicle preparations by solubilization in Triton X-100, and was purified in buffers containing that detergent. The purification employed chromatography on DEAE-cellulose, precipitation by 30% ethanol, and chromatography on hydroxyalapatite and DEAE-agarose. The most highly purified preparations of the enzyme were homogeneous in migration on polyacrylamide gels containing Triton X-100, at pH 9.5, where one band accounted for all of the protein and activity. Electrophoresis on polyacrylamide gels containing sodium dodecul sulfate showed 1 band of molecular weight 38,000, which accounted for over 75% of the protein on the gel. Because of requirements for either Triton X-100 or phospholipid for activity of the purified enzyme, it is difficult to estimate the level of purification achieved over isolated membrane vesicles. However, we estimate that the enzyme was purified some 30-fold over membrane vesicles, or some 300-fold over whole cells.
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PMID:The NADH dehydrogenase of the respiratory chain of Escherichia coli. I. Properties of the membrane-bound enzyme, its solubilization, and purification to near homogeneity. 78 86

A strain carrying a point mutation affecting the NADH dehydrogenase complex of Escherichia coli has been isolated and its properties examined. The gene carrying the mutation (designated ndh) was located on the E. coli chromosome at about minute 23 and was shown to be cotransducible with the pyrC gene. Strain carrying the ndh- allele were found to be unable to grow on mannitol and to grow very poorly on glucose unless the medium was supplemented with succinate, acetate or casamino acids. The following properties of strains carrying the ndh- allele were established which suggest that the mutation affects the NADH dehydrogenase complex but apparently not the primary dehydrogenase. Membrane preparations possess normal to elevated levels of D-lactate oxidase and succinate oxidase activities but NADH oxidase is absent. NADH is unable to reduce ubiquinone in the aerobic steady state and reduces cytochrome b very slowly when the membranes become anaerobic. NADH dehydrogenase, measured as NADH-dichlorophenolindophenol reductase is reduced but not absent. NADH oxidase is stimulated by menadione although not by Q-3 or MK-1 and in the presence of menadione, cytochrome b is reduced normally by NADH. Further mutants affected in NADH oxidase were isolated using a screening procedure based on the growth characteristics of the original ndh- strain. The mutantions carried by these strains were all cotransducible with the pyrC gene and the biochemical properties of the additional mutants were similar to those of the original mutant. The properties of the group of ndh- mutants established so far suggest that they are affected in the transfer of reducing equivalents from the NADH dehydrogenase complex to ubiquinone.
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PMID:Mutations affecting the reduced nicotinamide adenine dinucleotide dehydrogenase complex of Escherichia coli. 79 16

The fungicide dexon (p-dimethylaminobenzenediazosulfonate, Na-salt) inhibits the NADH oxidase activity of submitochondrial particles (ETP) from beef heart (semi-inhibition concentration 1.4 muM), while the succinate oxidase activity is unaffected. Measurements of the activity of several enzymatic partial reactions of the respiratory chain of ETP suggest that dexon acts directly on the flavine of NADH dehydrogenase. Soluble NADH-cytochrome c-oxidoreductase (MAHLER) and rotenone-insensitive NADH ubiquinone reductase are also inhibited by dexon. At low concentrations of dexon, inhibition of ETP starts slowly only after addition of NADH. Preincubation without NADH increases the amount of inhibition, but does not prevent the time delay. It is assumed that an electron flux through the respiratory chain, or reduction of flavine is prerequisite for the reaction of dexon with the action site. Furthermore, dexon inhibits the NADH dehydrogenase located at the outer surface of the inner membrane of plant mitochondria, accessible to extramitochondrial NADH and insensitive to rotenone, as has been shown on isolated mitochondria from cauliflower (Brassica oleracea L). In addition, dexon inhibits selectively the NADH dehydrogenase of the DT diaphorase (ERNSTER) from rat liver cytosol. In contrast, the dicoumarol-insensitive NADH dehydrogenase (ZINSMEYER et al.) from rat liver cytosol, the NADH-cytochrome b5-reductase (STRITTMATTER) from rat liver microsomes, the rotenone-insensitive NADH-cytochrome c-oxidoreductase of the outer membrane of rat liver mitochondria, soluble NADH-oxidase from Escherichia coli, and NADH-dehydrogenase from human erythrocytes are not inhibited. The results suggest that dexon is a group reagent to certain pyridine nucleotide-dependent flavine enzymes.
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PMID:[Action of the systemic fungicide dexon on several NADH dehydrogenases]. 82 48

Treating bovine epididymal spermatozoa with rutamycin or rotenone inhibited both respiration and motility supported by endogenous substrates. When oxidative phosphorylation had been blocked with various inhibitors, pyruvate was metabolized to yield ATP and restored motility. Fructose, which is metabolized via glycolysis to yield ATP, was also able to resuscitate the cells. Other substrates tested (lactate, acetate, alpha-ketoglutarate, or glyoxylate) were unable to restore motility in rutamycin-treated cells. In the presence of pyruvate, the phosphorylation uncoupler, carbonylcyanide-p-trifluoromethyoxphenylhydrazone, reduced motility and ATP to common levels in untreated cells or cells treated with rutamycin or rotenone. Pyruvate is thus metabolized to produce ATP by a pathway independent of oxidative phosphorylation associated with the electron transport chain. 5-Methoxyindole-2-carboxylic acid, an inhibitor of lipoyldehydrogenase, prevented the increase of motility and ATP in rutamycin-treated cells, indicating that alpha-keto acid oxidation is involved in the production of ATP from pyruvate when rutamycin is present. With pyruvate present, bongkrekic acid, antimycin A, and anaerobiosis eliminated motility, reduced ATP to low levels, and also significantly reduced the rate of pyruvate metabolism. Acetate was produced from pyruvate only when cellular ATP concentrations were low. Decreases in free carnitine concentrations showed that pyruvate initially used was converted to acetylcarnitine. The results indicate that the intramitochondrial lactate dehydrogenase X, which is unique to spermatozoa, allows the NADH resulting from pyruvate oxidation to reduce other pyruvate molecules to lactate. Pyruvate thus competes with, and can substitute for, the NADH dehydrogenase of the electron transport chain. Pyruvate rapidly repletes the acetylcarnitine pool under a variety of conditions.
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PMID:Pyruvate metabolism in bovine epididymal spermatozoa. 83 18

The topography of the inner mitochondrial membrane was investigated using inhibitors of electron transport on preparations of beef heart mitochondria and electron transport particles of opposite orientation. Reductions of juglone, ferricyanide, indophenol, coenzyme Q, duroquinone, and cytochrome c by NADH are inhibited to different extents on both sides of the membrane by the impermeant hydrophilic chelators bathophenanthroline sulfonate and orthophenanthroline. The extent of inhibition for each acceptor increased in the order given. At least two chelator-sensitive sites are present on each membrane face between the flavoprotein and coenzyme Q and a chelator-sensitive site is present on the matrix face between the sites of coenzyme Q and duroquinone interaction. Duroquinol oxidation in mitochondria only is stimulated by bathophenanthroline sulfonate. Juglone reduction is stimulated in electron transport particles (only) by p-hydroxymercuribenzenesulfonate, but after mercurial treatment, juglone reduction in both particles and mitochondria is more sensitive to bathophenanthroline sulfonate. Succinate dehydrogenase components are inhibited by hydrophilic orthophenanthroline or bathophenanthroline sulfonate in mitochondria only. Electron flow between the dehydrogenases of succinate and NADH occurs via a chelator-sensitive site located on the matrix face of the membrane. Inter-complex electron flow is prevented by rotenone or thenoyltrifluoroacetone. The lack of succinate-indophenol reductase inhibition by bathophenanthroline sulfonate in the presence of rotenone or thenoyltrifluoroacetone indicates that the rotenone-sensitive site may be located on the matrix face and demonstrates that electrons flow between the NADH and succinate dehydrogenases via a hydrophilic chelator and rotenone-thenoyltrifluoroacetone-sensitive site on the matrix face of the membrane. Inhibiton by hydrophilic chelators only in mitochondria indicates that succinate dehydrogenase as well as NADH dehydrogenase has a transmembranous orientation.
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PMID:Inhibition of mitochondrial electron transport by hydrophilic metal chelators. Determination of dehydrogenase topography. 94 64

1. Several ring-substituted derivatives of diphenyleneiodonium catalyse the exchange of Cl- and OH- ions across the inner membrane of rat liver mitochondria. They also inhibit state 3 and state 3u oxidations of glutamate plus malate in the presence of Cl- more than in its absence. Most have activities similar to diphenyleneiodonium, although 2,4-dichlorodiphenyleneiodonium is up to 50 times more active. 2. Diphenyleneiodonium inhibits soluble rat liver NADH dehydrogenase and NADH oxidation by rat liver sub-mitochondrial particles directly; 2,4-dichlorodiphenyleneiodonium is only about twice as inhibitory. 3. Liver mitochondria contain two classes of binding sites for diphenylene[125I]iodonium, namely high-affinity sites with an affinity constant of 3 X 10(5) M-1 (1--2 nmol/mg of protein), and low-affinity sites with an affinity constant of 1.3 X 10(3) M-1 (80 nmol/mg of protein). Both sites occur in hepatocytes with a relative enrichment of the low-affinity site. Nadh dehydrogenase preparations only apparently contain high-affinity binding sites. Only low-affinity sites occur in erythrocytes. 4. 2,4-Dichlorodiphenyleneiodonium competes with diphenylene[125I]iodonium for both low- and high-affinity sites, whereas tri-n-propyltin only competes for the low-affinity sites. 5. The high-affinity sites are apparently associated with NADH dehydrogenase and the low-affinity sites probably represent electrostatic binding of diphenylene[125I]iodonium to phospholipids. The high-affinity site does not appear to be associated with a rate-limiting stage of NADH oxidation.
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PMID:The effects of diphenyleneiodonium on mitochondrial reactions. Relation of binding of diphenylene[125I]iodonium to mitochondria to the extent of inhibition of oxygen uptake. 98 31


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