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

---

Query: EC:1.6.5.2 (NQO1)
6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The respiratory chain of a marine bacterium, Vibrio alginolyticus, required Na+ for maximum activity, and the site of Na+ -dependent activation was localized on the NADH-quinone reductase segment. The Na+ -dependent NADH-quinone reductase extruded Na+ as a direct result of redox reaction. It was composed of three subunits, alpha, beta, and gamma, with apparent Mr of 52, 46, and 32 KDa, respectively. The reduction of ubiquinone-1 to ubiquinol proceeded via ubisemiquinone radicals. The former reaction was catalyzed by the FAD-containing beta subunit. This reaction showed no specific requirement for Na+. For the formation of ubiquinol, the presence of the gamma subunit and the FMN-containing alpha subunit was essential. The latter reaction specifically required Na+ for activity and was strongly inhibited by 2-n-heptyl-4-hydroxyquinoline N-oxide. It was assigned to the coupling site for Na+ transport. The mode of energy coupling of redox-driven Na+ pump was compared with those of decarboxylase- and ATP-driven Na+ pumps found in other bacteria.
...
PMID:Sodium-transport NADH-quinone reductase of a marine Vibrio alginolyticus. 268 59

Lactoquinomycin A (LQM-A), an antibiotic containing a quinone moiety in the molecule, inhibited biosyntheses of DNA, RNA and protein to a similar extent in doxorubicin-resistant mouse leukemia L5178Y cells at concentrations higher than 0.08 micrograms/ml. The antibiotic caused cell death in a short period of incubation and the degree of cell death correlated with that of the inhibition of macromolecular syntheses, suggesting that the inhibition of macromolecular syntheses was not a primary effect of LQM-A. LQM-A served as a good electron acceptor, when cytochrome c reductase was used as a quinone reductase. The treatment of the cells with LQM-A significantly reduced cellular NADH and ATP levels. The generation of superoxide radical by LQM-A in cell lysate was observed by reduction of nitro blue tetrazolium, and the production of hydroxyl radical was confirmed by electron spin resonance. The importance of radical formation for the cytotoxicity of LQM-A is discussed.
...
PMID:Mechanism of action of lactoquinomycin A with special reference to the radical formation. 284 12

Electron transfer activities and steady state reduction levels of Fe-S centers of NADH-Q oxidoreductase were measured in mitochondria, submitochondrial particles (ETPH), and complex I after treatment with various reagents. p-Chloromercuribenzenesulfonate destroyed the signal from center N-4 (gx = 1.88) in ETPH but not in mitochondria, showing that N-4 is accessible only from the matrix side of the inner membrane. N-Bromosuccinimide also destroyed the signal from N-4 but without inhibiting rotenone-sensitive electron transfer to quinone, suggesting a branched pathway for electron transfer. Diethylpyrocarbonate caused oxidation of N-3 and N-4 in the steady state without changing N-1, suggesting N-1 is before N-3 and N-4. Difluorodinitrobenzene and dicyclohexylcarbodiimide inhibited oxidation of all Fe-S centers and tetranitromethane inhibited reduction of all Fe-S centers. Titrations of the rate of superoxide (O2-) generation in rotenone-treated submitochondrial particles were similar with the ratio [NADH]/[NAD] and that of 3-acetyl pyridine adenine nucleotide in spite of different midpoint potentials of the two couples. On reaction with inhibitors the inhibition of O2- formation was similar to that of ferricyanide reductase rather than quinone reductase. The rate of O2- formation during ATP-driven reverse electron transfer was 16% of the rate observed with NADH. The presence of NAD increased the rate to 83%. The results suggest that bound, reduced nucleotide, probably E-NAD., is the main source of O2- in NADH dehydrogenase. The effect of ATP on the reduction levels of Fe-S centers in well-coupled ETPH was measured by equilibrating with either NADH/NAD or succinate/fumarate redox couples. With NADH/NAD none of the Fe-S centers showed ATP induced changes, but with succinate/fumarate all centers showed ATP-driven reduction with or without NAD present. The effect on N-2 was smaller than that on N-1, N-3, and N-4. These observations indicate that the major coupling interaction is between N-2 and the low potential centers, N-1, N-3, and N-4. Possible schemes of coupling in this segment are discussed.
...
PMID:Studies on the electron transfer pathway, topography of iron-sulfur centers, and site of coupling in NADH-Q oxidoreductase. 284 70

The concept is developed according to which Na+, like H+, can play the role of a coupling ion in energy-transducing biomembranes. This idea is based on observations that (i) Na+ can be extruded from the cell by primary pumps (Na-motive NADH-quinone reductase, decarboxylase or ATPase), and (ii) the downhill Na+ flux into the cell can be coupled with the performance of all the three types of membrane-linked work i.e. chemical (ATP synthesis), osmotic (accumulation of solutes) and mechanical (motility). Marine alkalotolerant Vibrio alginolyticus represents the first example of such a complete sodium cycle pattern. Simplified versions of the sodium cycle or some of its constituents are found in the cytoplasmic membrane of a great variety of taxa including anaerobic, aerobic and photosynthetic bacteria, cyanobacteria and animals; this fact indicates that Na+ energetics should be regarded as a common case, rather than a rare exception applied to some natural niches only.
...
PMID:Membrane-linked energy transductions. Bioenergetic functions of sodium: H+ is not unique as a coupling ion. 286 40

Wistar rats (110-125 g) were irradiated with a single dose of 500 R. Histochemical studies were done concerning the glycoproteins (GP) of sublingual glands, gastric, small intestine and colon mucosa, and some intestinal enzymes: acid and alkaline phosphatase (ACP, ALP) leucineaminopeptidase (LAP), Mg-dependent ATP-ase, NADH-diaphorase, lactic dehydrogenase (LDH). After irradiation all these reactions were diminished, with a maximal effect between 3-5 days. This impairment is in accord with the maximal lethality in this interval after such a degree of irradiation that produced the gastrointestinal syndrome. Cocarboxylase, a radioprotector, improved these changes regarding the structures of the small intestine and also the GP of sublingual glands, stomach, small intestine and colon, demonstrating there its efficiency.
...
PMID:Histochemical changes in the digestive tract in irradiated rats. 311 66

The individual effects of two putative metabolites of primaquine (5,6-dihydroxyprimaquine and 5,6-dihydroxy-8-aminoquinoline) on the hexose monophosphate shunt (HMS) and on the ATP-dependent proteolytic system which rapidly degrades oxidized erythrocyte protein were measured in intact red blood cells in vitro from two blood donors. In red cells treated with nitrite (1-40 mM) or phenylhydrazine (0.01-10 mM), proteolytic activity was detected only with concentrations (7.5 mM NaNO2 and 0.25 mM phenylhydrazine) causing greater than 15-fold elevation of HMS activity, and glucose-6-phosphate dehydrogenase (G6PD)-deficient (25% of normal activity) red cell suspensions thus treated showed approximately 30% greater proteolysis. G6PD-normal and deficient red cells treated with the primaquine analogs, however, did not experience proteolysis with concentrations (0.25 mM) in excess of those causing 17-fold elevation of HMS activity. Stimulation of the HMS by the primaquine analogs thus appears unrelated to an erythrotoxic oxidative stress. Methylene blue is known to cause an elevation of HMS activity through direct and diaphorase II-dependent oxidation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) which is independent of injurious oxidative stress. It was found that the putative primaquine metabolites also caused direct and diaphorase II-dependent oxidation of NADPH in dilute hemolysate, thus suggesting that the putative primaquine metabolites have a methylene blue-like redox disposition in red blood cells. Results obtained in this study suggest that the hemolytic toxicity of primaquine may be unrelated to processes which lead to oxidative deterioration of red cell protein.
...
PMID:Oxidative activity of hydroxylated primaquine analogs. Non-toxicity to glucose-6-phosphate dehydrogenase-deficient human red blood cells in vitro. 375 45

A histochemical study of the metabolism of rat renal arteries and arterioles. Rat renal arteries and arterioles were examined histochemically to determine their metabolic profiles. Succinate, malate and NAD-isocitrate dehydrogenase, cytochrome oxidase and ubiquinone were assessed to determine aerobic metabolism. Glucose-6-phosphate dehydrogenase and DPN diaphorase were evaluated to determine hexose-monophosphate-shunt activity. Anaerobic metabolism was evaluated via lactate dehydrogenase, and the substrate, glycogen. Gomori's lipase, beta-hydroxybutyrate dehydrogenase and amounts of neutral fat and free fatty acids were assessed as indicators of lipid utilization. Myosin ATPase activity was evaluated as an index of ATP utilization for contraction. Deoxyribonucleic and ribonucleic acids were appraised as indicators of protein synthesis. In general, the oxidative enzymes and myosin ATPase demonstrate considerable activity in renal arteries and arterioles which suggests aerobic metabolism and ATP usage. Renal arteries and arterioles also appear capable of anaerobic metabolism as indicated by strong lactate dehydrogenase reactivity and by the presence of slight to moderate quantities of glycogen, while high levels of glucose-6-phosphate dehydrogenase and moderate amounts of deoxyribonucleic acid suggest a potential for beta-hydroxybutyrate dehydrogenase, minimal lipase activity, and the absence of fatty acids with substantial amounts of neutral fat, indicate limited lipid catabolism.
...
PMID:A histochemical study of the metabolism of rat renal arteries and arterioles. 620 11

The reduction and the potential autoxidation of quinoid compounds may be viewed as taking place in three cell compartments. In microsomal fractions (endoplasmic reticulum) one-electron reduction by NAPDH-cytochrome P450 reductase leads to the formation of semiquinones which rapidly react with oxygen to form the parent quinone and superoxide anions. The formation of superoxide through this futile cycle leads ultimately to other damaging species (H2O2 and .OH). A similar futile cycle in mitochondria involves NADH dehydrogenase. In this instance, mitochondria initiation of such a cycle with quinones results not only in the formation of toxic radical species but also in the diversion of electrons from phosphorylating pathways. The consequent diminution of cellular ATP may have as important a consequence with respect to the toxicity of quinones as the generation of radicals. Finally, cytosolic DT diaphorase, which carries out a two-electron reduction of quinones to more stable hydroquinones, may compete with the one-electron systems and participate in the detoxification of quinones by supplying hydroquinones for conjugation reactions. The extent of quinone-induced damage may thus vary from cell to cell depending on the integration of these pathways.
...
PMID:Futile redox cycling: implications for oxygen radical toxicity. 631 61

By histochemical methods and electron microscopy, the spleen of copper-loaded rat was investigated. Oxidoreducing enzymes (diaphorase, succinate dehydrogenase, lactate dehydrogenase, prolineoxidase, hydroxyproline epimerase) and phosphatases (acid, ATP-ases) were tested. In general, in the intoxicated rat, the oxidases and dehydrogenases were depressed in the splenic cells, except macrophages and endothelial cells. Prolineoxidase and hydroxyproline epimerase activities increased in reticular cells and phosphatases displayed a strong activity in all the splenic structures. Ultrastructural modifications appeared in connective fibers and some connective cells.
...
PMID:Histochemical and ultrastructural data in the spleen of the copper-intoxicated rat. 646 25

Biochemical alterations in guinea pig lungs caused by hematite dust were followed at 150 days after intratracheal administration of the dust. In vivo dust exposure caused a significant increase in mitochondrial protein content and cytochrome c oxidase activity whereas diaphorase activity remained unaltered. Mitochondria from the exposed animals were apparently in a swollen state and their contraction profile upon the addition of ATP reflected permeability changes. However, in vitro dust caused no significant alterations. Significant increases in glycogen content along with an insignificant decrease in glycogen phosphorylase activity were also observed in hematite-treated guinea pig lungs. Decrease in drug-metabolizing enzymes such as aniline hydroxylase and tyrosine aminotransferase activities were also evident in the postmitochondrial fraction of the siderotic lungs. [3H]Leucine-incorporation studies showed increased protein synthesis in the postmitochondrial fraction. Increase in protein synthesis in mitochondria was only marginal whereas in whole homogenate it decreased considerably. Experiments employing dust tagged with radioactive iron indicated the rapid mobilization of iron from lung and its distribution to various organs. The presence of iron-binding protein was confirmed by employing Sephadex gel-filtration techniques.
...
PMID:Biochemical studies on the toxicity of hematite dust. 664 70


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---