Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Aspergillus nidulans, the nitrate assimilatory pathway is regulated by a variety of agents, one being the autogenous enzyme nitrate reductase. A major subunit of the enzyme which is specified by the niaD structural gene and is implicated in autogenous control exhibits both nitrate inducible diaphorase activity and ammonium repression. The former was used to test the extent to which alterations in the niaD specified protomer might affect its formation in selected niaD point and deletion mutants. Enzyme preparations from the wild type and mutant strains were compared on the basis of nitrate inducible co-activities and their reaction to specific monoclonal antibodies (MABS). Proteins in partially purified mycelial extracts were subjected to Western blot analyses with three MABs to functional native enzyme. Extracts of niaD point mutants exhibited nitrate induced co-activities which matched those of the wild type while those from deletion mutants were diminished or totally inactive. Nitrate reductase, from the wild type and specific cofactor mutants, shares an epitope common to both the monomeric and dimeric form in the case of one MAB, and exhibits epitopes unique to one or the other form in the case of the other two forms. Enzyme-antibody interaction occurs with or without inhibition of catalytic activity depending on the MAB involved.
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PMID:Monoclonal antibody probes for the niaD specified subunit in the NADPH-nitrate reductase from Aspergillus nidulans. 332 53

In vivo complementation between different wild and mutant strains defective for nitrate assimilation has been performed by isolating diploid strains from the appropriate crosses. Twenty-two diploids homozygous or heterozygous with respect to nitrate reduction and able to grow on nitrate medium were obtained and their diploid character demonstrated from analyses of mating type, cell volume, nuclear size and progeny of crosses with haploid wild-type. All diploids were assayed for overall- and terminal-nitrate reductase (NR) activity and for the occurrence of the NR-diaphorase subunit. Data on NR activities in heterozygotes carrying mutation(s) in structural gene(s) (nit-1 or nit-1a, nit-1b) agree with the heteromultimeric nature of the enzyme complex previously described (Franco et al. (1984) EMBO J 3: 1403-1407), and indicate that subunits are exchangeable to form hybrid enzymes. In addition, in vitro complementation tests with mutant nit-1 of C. reinhardtii indicate that this mutant has defective NR-diaphorase subunits but intact terminal subunits. Super-repression caused by the mutant allele nit-2 is suppressed by the wild allele in heterozygotes, which suggests a positive control by the nit-2 product on structural gene(s) transcription. Mutant alleles of genes for the biosynthesis of molybdenum-containing cofactor, either nit-4 or nit-5 and nit-6, were recessive in diploids carrying them. The mutant allele of nit-3, from strain 307, was codominant in all heterozygotes suggesting that nit-3 codes for a protein whose activity is limiting for the molybdenum-cofactor biosynthetic pathway.
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PMID:In vivo complementation analysis of nitrate reductase-deficient mutants in Chlamydomonas reinhardtii. 344 23

Hepatocyte nodules in the rat exhibit a unique biochemical pattern which is characterized by a decrease in Phase I and an increase in Phase II components of the drug-metabolizing system. The present study was designed to determine whether this biochemical pattern is unique for rat hepatocyte nodules or is a property of the liver cell, but expressed only when the liver cell is perturbed. The results obtained indicate that lead nitrate (5 or 10 mumol/100 g body wt), an inducer of liver cell proliferation, caused a decrease in Phase I components such as microsomal cytochromes P-450 and in the activity of aminopyrine N-demethylase, while it caused an increase in Phase II components such as glutathione, and in the activities of glutathione-S-transferase and DT-diaphorase in rat liver. Of particular interest was the finding in liver cytosol of lead-treated rats of an increased content of a polypeptide which cross-reacts with the anti-rat placental form of glutathione-S-transferase. Recently, it has been shown that rat hepatocyte nodules exhibited an increased content of the placental form of glutathione-S-transferase. Thus, the results suggest that some chemicals, such as lead nitrate, can induce in rat liver a biochemical pattern similar in certain respects to that exhibited by hepatic nodules. These chemicals may be used as model compounds to understand the molecular mechanism(s) underlying the induction of new and unique biochemical machinery seen in hepatic nodules.
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PMID:Lead nitrate induces certain biochemical properties characteristic of hepatocyte nodules. 375 67

Isolated membranes of Bacillus stearothermophilus 2184D can be disrupted by treatment with sodium dodecyl sulfate (SDS). This disruption is attended by a decreased turbidity of membrane suspensions and a differential loss of activities of the electron transport system. Reduced methyl viologen (MVH)-nitrate reductase activity is insensitive to SDS treatment, whereas reduced nicotinamide adenine dinucleotide (NADH)-nitrate reductase and cyanide-sensitive NADH oxidase activities are decreased by 80% at an SDS concentration of 0.5 mg/mg of membrane protein. NADH-menadione reductase activity is unaffected at this SDS concentration, but at higher detergent levels it also decreases in activity. The abilities of NADH to reduce and nitrate to oxidize the cytochrome components of the membrane were also decreased after SDS treatment. Dilution of solubilized membrane in buffer containing divalent cation results in formation of an aggregate with an increased turbidity and reconstituted NADH-nitrate reductase and cyanide-sensitive NADH oxidase activities. Of several cations tested, magnesium was the most effective, and the reconstitution process was pH-dependent with an optimum at pH 7.4. Intact and aggregated membranes had similar densities and cytochrome contents, and the sensitivity of NADH-nitrate reductase to several inhibitors was similar in intact and reconstituted membranes.
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PMID:Physical aggregation and functional reconstitution of solubilized membranes of Bacillus stearothermophilus. 433 10

Experiments were performed to determine whether conditions which cause the rapid loss of nitrate reductase activity in Neurospora crassa mycelia were accompanied by the loss of antigenically detectable nitrate reductase protein. When mycelia with nitrate reductase activity were transferred to ammonia media, there was a rapid loss in the reduced nicotinamide adenine dinucleotide-nitrate reductase activity plus the parallel loss of the reduced nicotinamide adenine dinucleotide-diaphorase and the reduced methyl viologen-nitrate reductase activities associated with the nitrate reductase. In addition, there was the loss of cross-reacting material to anti-nitrate reductase antisera that was concomitant with the loss of nitrate reductase activity. When mycelia were exposed to either ammonia plus cycloheximide, nitrate plus cycloheximide, or nitrogen-free media, or to media which lacked an assimilable carbon source, the amount of cross-reacting material declined in concert with the nitrate reductase activity. The mutant nit-6, which lacks nitrite reductase activity, was exposed to ammonia or nitrate plus cycloheximide media. The nitrate reductase and the amount of cross-reacting material declined together as in the wild-type mycelia. We conclude that the loss of nitrate reductase activity was accompanied by the specific loss of this protein and that no pool of inactivated nitrate reductase molecules existed.
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PMID:Repression of nitrate reductase activity and loss of antigenically detectable protein in Neurospora crassa. 644 48

Nitrate reductase from the yeast Candida nitratophila was found to contain one molecule of cytochrome b557 and one atom of molybdenum per subunit. FAD/haem-dependent diaphorase activity (haem domain) was associated with a 40 kDa tryptic fragment of the subunit. The 50 amino-terminal residues of this fragment were determined, and the sequence did not show significant similarity to deduced sequences of other nitrate reductases previously published. Increasing ionic strength in vitro had a stimulatory effect on enzymic activity via stimulation of the molybdenum-dependent terminal nitrate-reducing activity. Stimulation of activity by exogenous protein (bovine serum albumin or casein) also appeared to be an ionic effect. Stimulation of catalytic activity by phosphate was a separate effect.
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PMID:Further characterization of the assimilatory nitrate reductase from the yeast Candida nitratophila. 847 56

To investigate the role of nitric oxide in the cerebellar degeneration during methylmercury intoxication, interaction of the change in nitric oxide synthase activity and degeneration of the granular layer neurons was examined in rats after methylmercury administration. Both reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase and anti-nitric oxide synthase antibody staining, and measurement of glutamate, and nitrite and nitrate levels in the cerebrospinal fluid were performed after oral administration of 5 mg/kg of methylmercury for 12 days. Nitric oxide synthase activity in the cerebellum was also assayed by monitoring the conversion of arginine to citrulline. Methylmercury levels in the blood and the cerebellum gradually increased up to day 13 after the initial methylmercury administration, and neurological disturbances, such as hindleg crossing and abnormal gait, were observed from day 17 after administration. Although a significant decrease in the number of granular layer neurons was recognized at day 84, no such decrease either in NADPH-diaphorase or anti-nitric oxide synthase antibody positive neurons was seen. Glutamate levels in the cerebrospinal fluid transiently increased at day 9 and finally decreased at day 84. Also a transient increase in both nitrite and nitrate levels in the cerebrospinal fluid and nitric oxide synthase activity in the cerebellum was seen prior to the start of degeneration of the granular layer neurons. These results suggest that nitric oxide may play an important role in the degeneration process of the granular layer neurons during methylmercury intoxication.
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PMID:Role of nitric oxide in the cerebellar degeneration during methylmercury intoxication. 910 26

The assimilatory nitrate reductase from the phototrophic bacterium Rhodobacter capsulatus has been purified to electrophoretic homogeneity and its molecular and kinetic parameters determined. The native nitrate reductase is a dimer of 144 kDa composed of two subunits of 46 and 95 kDa. The purified enzyme catalyzes the electron transfer from NADH, reduced bromophenol blue or reduced viologens to nitrate. The nitrate reductase contains 1 mol FAD per mole of enzyme and also reduces cytochrome c or dichlorophenol indophenol with NADH as the electron donor. The diaphorase activity is located in the small subunit.
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PMID:The assimilatory nitrate reductase from the phototrophic bacterium, Rhodobacter capsulatus E1F1, is a flavoprotein. 930 29

Our objective was to show the presence of nitric oxide synthase (NOS) in the mammary glands of lactating rats and to determine the role that nitric oxide plays in lactation of humans. We used the nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase reaction and immunostaining on fresh frozen breast tissue obtained from lactating Wistar rats (13-18 wk old, 320-380 g, 3-4 d after parturition, first pregnancy). The breast tissues positive for NADPH diaphorase staining were the mammary gland, muscle, sebaceous gland, epidermis, and endothelium of the lactiferous ducts and blood vessels. These findings corresponded to tissues that were NOS-immunoreactive. The NOS detected in the mammary glands was the constitutive NOS. The finding of positive anti-NOS immunoreactivity and of positive NADPH diaphorase activity in the cells of the rat mammary glands leads us to conclude that nitric oxide is synthesized in mammary glands of rats. The high nitric oxide activity in the human breast was previously reported by measuring the total concentration of nitrite plus nitrate, biopterin, and neopterin in human milk. These results suggest that nitric oxide plays a role in the secretion of human breast milk.
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PMID:The presence of nitric oxide synthase in the mammary glands of lactating rats. 970 14

We investigated the pathophysiological role of nitric oxide synthesized by inducible nitric oxide synthase in the brain, by injecting lipopolysaccharide directly into the rat cerebral cortex/hippocampus. The levels of nitric oxide metabolites, nitrite and nitrate, began to increase in a dose-dependent manner with a 3-h lag, and reached approximately seven-fold the basal levels 8 h after the direct injection of lipopolysaccharide (5 microg). The lipopolysaccharide-induced increase in nitrite and nitrate levels was inhibited by treatment with the specific inducible nitric oxide synthase inhibitor aminoguanidine. The protein synthesis inhibitor cycloheximide delayed the onset of the increase in nitric oxide metabolite levels, and reduced the peak levels. Lipopolysaccharide increased Ca2+-independent, but not Ca2+-dependent, nitric oxide synthase activity in the brain. Intense nicotinamide adenine dinucleotide phosphate-diaphorase activity was observed in round cells in the vicinity of the site of injection of lipopolysaccharide 8 h after the injection. Neuronal death was observed seven days after the injection of lipopolysaccharide. Spatial memory, as assessed by performance in a water maze task and spontaneous alternation behavior in a Y-maze, was significantly impaired in rats which had had previous bilateral injections of lipopolysaccharide into the hippocampus. The lipopolysaccharide-induced neuronal death and spatial memory impairments were prevented by aminoguanidine. These results suggest that direct injection of lipopolysaccharide into the brain causes an induction of inducible nitric oxide synthase in vivo. Furthermore, it is suggested that nitric oxide produced by inducible nitric oxide synthase is responsible for the lipopolysaccharide-induced brain dysfunction.
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PMID:Brain dysfunction associated with an induction of nitric oxide synthase following an intracerebral injection of lipopolysaccharide in rats. 1005 Dec 7


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