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

The cytoplasmic, NAD-reducing hydrogenase (SH) of Alcaligenes eutrophus H16 is a heterotetrameric enzyme which contains several cofactors and undergoes a complex maturation during biogenesis. HoxH is the Ni-carrying subunit, and together with HoxY it forms the hydrogenase dimer. HoxF and HoxU represent the flavin-containing diaphorase moiety, which is closely related to NADH:ubiquinone oxidoreductase and mediates NADH oxidation. A variety of mutations were introduced into the four SH structural genes to obtain mutant enzymes composed of monomeric and dimeric forms. A deletion removing most of hoxF, hoxU, and hoxY led to the expression of a HoxH monomer derivative which was proteolytically processed at the C terminus like the wild-type polypeptide. While the hydrogenase dimer, produced by a strain deleted of hoxF and hoxU, displayed H2-dependent dye-reducing activity, the monomeric form did not mediate the activation of H2, although nickel was incorporated into HoxH. Deletion of hoxH and hoxY led to the production of HoxFU dimers which displayed NADH:oxidoreductase activity. Mixing the hydrogenase and the diaphorase moieties in vitro reconstituted the structure and catalytic function of the SH holoenzyme.
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PMID:Subforms and in vitro reconstitution of the NAD-reducing hydrogenase of Alcaligenes eutrophus. 949 38

A fragment of the NDH-F subunit of the plastid NAD(P)H dehydrogenase complex (NAD(P)H-plastoquinone-oxidoreductase) from barley was expressed as a fusion protein in Escherichia coli and an antibody to the fusion protein was prepared. Western blot analysis using the anti-NDH-F antibody showed specificity towards a plastid polypeptide of approximately 70 kDa present in both photosynthetic and non-photosynthetic barley tissue. The polypeptide was found in thylakoid membranes of green leaves whereas in etiolated leaves it was shown to be associated with the membrane fraction of etioplasts. NDH-F levels were higher in roots and etiolated tissue than in greening or young leaves. During leaf ontogeny, NDH-F levels decreased from young to mature tissue but increased during senescence. The accumulation of NDH-F in thylakoids of young leaves was stimulated by photooxidative treatment. The results indicate a high degree of expression of plastid ndh genes (which encode NAD(P)H dehydrogenase subunits) in non-photosynthetic plastids and under conditions which impair the photosynthetic activity of chloroplasts. In addition to its putative implication in photosynthetic electron transport, a non-photosynthetic role, such as chlororespiration, is proposed for the plastid NAD(P)H dehydrogenase complex.
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PMID:Expression of the plastid ndhF gene product in photosynthetic and non-photosynthetic tissues of developing barley seedlings. 952 68

Barley (Hordeum vulgare L.) leaves were used to isolate and characterize the chloroplast NAD(P)H dehydrogenase complex. The stroma fraction and the thylakoid fraction solubilized with sodium deoxycholate were analyzed by native polyacrylamide gel electrophoresis, and the enzymes detected with NADH and nitroblue tetrazolium were electroeluted. The enzymes electroeluted from band S from the stroma fraction and from bands T1 (ET1) and T2 from the thylakoid fraction solubilized with sodium deoxycholate had ferredoxin-NADP oxidoreductase (FNR; EC 1.18.1.2) and NAD(P)H-FeCN oxidoreductase (NAD[P]H-FeCNR) activities. Their NADPH-FeCNR activities were inhibited by 2'-monophosphoadenosine-5'-diphosphoribose and by enzyme incubation with p-chloromercuriphenylsulfonic acid (p-CMPS), NADPH, and p-CMPS plus NADPH. They presented Michaelis constant NADPH values that were similar to those of FNRs from several sources. Their NADH-FeCNR activities, however, were not inhibited by 2'-monophosphoadenosine-5'-diphosphoribose but were weakly inhibited by enzyme incubation with NADH, p-CMPS, and p-CMPS plus NADH. We found that only ET1 contained two polypeptides of 29 and 35 kD, which reacted with the antibodies raised against the mitochondrial complex I TYKY subunit and the chloroplast ndhA gene product, respectively. However, all three enzymes contained two polypeptides of 35 and 53 kD, which reacted with the antibodies raised against barley FNR and the NADH-binding 51-kD polypeptide of the mitochondrial complex I, respectively. The results suggest that ET1 is the FNR-containing thylakoidal NAD(P)H dehydrogenase complex.
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PMID:Association of ferredoxin-NADP oxidoreductase with the chloroplastic pyridine nucleotide dehydrogenase complex in barley leaves 957 93

The distribution of nitrergic neurons was investigated by using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry in wholemount preparations of the urinary bladder in guinea pigs. Both NADPH-d+ and NOS+ neurons were located predominantly in the bladder base. Double staining showed that 70.9% of the NADPH-d+ neurons coexpressed NOS. Acetylcholinesterase histochemistry revealed that a majority of the intramural neurons were reactive, and about half of them (51.4%) were double labelled for NOS. Tyrosine hydroxylase-positive neurons were also distributed mainly in the bladder base but in a neuronal population that was separate from the preponderant NADPH-d+ neurons. Vasoactive intestinal polypeptide immunoreactivity was also detected in the some of intramural ganglion cells, in which 21.3% of them coexpressed NADPH-d. Calcitonin gene-related peptide and substance P immunoreactivities were confined to nerve fibers, often in close association with NADPH-d+ cells or extended along the blood vessels. These results have demonstrated the colocalization of NADPH-d and NOS in the majority of intramural ganglion cells. Many of the nitrergic neurons are apparently cholinergic, indicating that they are parasympathetic postganglionic neurons, and this underscores NO as the major neuromodulator in the parasympathetic nerves in the bladder walls. The localization of vasoactive intestinal polypeptide in nitrergic neurons suggests that the peptide may complement NO for regulation of micturition reflex. The close relationship of NADPH-d-reactive intramural neurons with calcitonin gene-related peptide and substance P fibers, most probably derived from dorsal root ganglion cells, suggests that NO released from the local neurons may exert its influence on the sensory neural pathways in the urinary bladder.
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PMID:Colocalization of nitric oxide synthase and some neurotransmitters in the intramural ganglia of the guinea pig urinary bladder. 959 May 57

Succinate:quinone reductase is a membrane-bound enzyme of the citric acid cycle and the respiratory chain. Carboxin is a potent inhibitor of the enzyme of certain organisms. The bacterium Paracoccus denitrificans was found to be sensitive to carboxin in vivo, and mutants that grow in the presence of 3'-methyl carboxin were isolated. Membranes of the mutants showed resistant succinate:quinone reductase activity. The mutation conferring carboxin resistance was identified in four mutants. They contained the same missense mutation in the sdhD gene, which encodes one of two membrane-intrinsic polypeptides of the succinate:quinone reductase complex. The mutation causes an Asp to Gly replacement at position 89 in the SdhD polypeptide. P. denitrificans strains that overproduced wild-type or mutant enzymes were constructed. Enzymic properties of the purified enzymes were analyzed. The apparent Km for quinone (DPB) and the sensitivity to thenoyltrifluoroacetone was normal for the carboxin-resistant enzyme, but the succinate:quinone reductase activity was lower than for the wild-type enzyme. Mutations conferring carboxin resistance indicate the region on the enzyme where the inhibitor binds. A previously reported His to Leu replacement close to the [3Fe-4S] cluster in the iron-sulfur protein of Ustilago maydis succinate:quinone reductase confers resistance to carboxin and thenoyltrifluoroacetone. The Asp to Gly replacement in the P. denitrificans SdhD polypeptide, identified in this study to confer resistance to carboxin but not to thenoyltrifluoroacetone, is in a predicted cytoplasmic loop connecting two transmembrane segments. It is likely that this loop is located in the neighborhood of the [3Fe-4S] cluster.
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PMID:Carboxin resistance in Paracoccus denitrificans conferred by a mutation in the membrane-anchor domain of succinate:quinone reductase. 963

The aim of the present study was to analyze the neurochemical properties of the centrifugal visual system (CVS) of the quail using an immunohistochemical approach by testing 16 neuropeptides (angiotensin: ANG, bradykinin: BK, cholecystokinin, dynorphin, L and M-enkephalin, beta-endorphin: beta-END, galanin, alpha-neoendorphin, neurokinin A, neuropeptide Y (NPY), ocytocin, somatostatin, substance P, vasopressin, vasoactive intestinal polypeptide) and three neurotransmitters or their synthetic enzymes (choline acetyltransferase: ChAT, tyrosine hydroxylase: TH, serotonin: 5-HT and nitric oxide synthase: NOS, including the histochemical nicotinamide adenine dinucleotide phosphate diaphorase technique). For each substance, the somatic and afferent fiber and terminal labeling was analyzed within the nucleus isthmo-opticus (NIO) and the ectopic area (EA) and compared with that of retinopetal cell bodies labeled retrogradely with RITC following its intraocular injection (double-labeling procedure). The results showed that none of the centrifugal neurons were reactive to any of the substances tested. In contrast, all with the exception of ANG, BK and beta-END, labeled fibers and terminals within the EA and only four (ChAT, 5-HT, NPY and NOS) within the NIO. Possible sources of these immunoreactive fibers terminating in the NIO and EA were investigated by mapping the somatic immunolabeling of the different substances within brainstem regions previously shown by Miceli and other authors to project upon the centrifugal neurons. The data suggests that, besides the rapid retino-tecto-NIO-retinal loop, which facilitates the transfer of meaningful or more relevant information within particular portions of the visual field, the multiple afferent input which stems from various brainstem regions utilizes a wide range of neuroactive substances. Some of these afferent projections upon the centrifugal neurons appear to belong to nonspecific systems which might play a role in modulating the excitability of centrifugal neurons as a function of arousal.
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PMID:An immunohistochemical study of putative neuromodulators and transmitters in the centrifugal visual system of the quail (Coturnix japonica). 971 61

The distribution of nitric oxide synthase (NOS)-, choline acetyltransferase (ChAT)-, and vasoactive intestinal polypeptide (VIP)-immunoreactivities, and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)-reactivities in the sphenopalatine ganglia (SPG), and perivascular nerves in middle cerebral arteries of the pig was investigated by double-staining techniques using combined immunofluorescence and histochemistry methods. In the SPG, almost all ganglionic cells were NOS-immunoreactive (I) and NADPHd-positive, and both NOS immunoreactivities and NADPHd reactivities were completely co-localized. ChAT-I ganglionic cells accounted for 75%, while VIP-I ganglionic cells represented 42% of all ganglionic cells. Almost all VIP immunoreactivities were co-localized with ChAT immunoreactivities, and all ganglionic cells that were VIP-I and/or ChAT-I were NOS-I and NADPHd-reactive. None of the ganglionic cells in the SPG were immunoreactive to calcitonin gene-related peptide (CGRP). CGRP immunoreactivities, however, were found to surround some ganglionic cells. In middle cerebral arteries, all adventitial NOS-I bundles and fine fibers were coincident with NADPHd fibers. Almost all adventitial ChAT-I bundles and thin fibers, and VIP-I mesh-like fibers stained positively for NADPHd, while the mesh-like NADPHd fine fibers were not ChAT-I. Simultaneous labeling using antibodies against VIP and ChAT further indicated that VIP-I fibers were closer than ChAT-I fibers to the smooth muscle. In rare occasions, perivascular fibers were found to be stained for both ChAT and VIP, showing that most ChAT-I and VIP-I fibers were not coincident. These results suggest that ChAT and VIP are rarely co-localized in perivascular nerves in middle cerebral arteries, and point out that the neurotransmitter and the modulator that are co-localized within the same nerve cell body may distribute totally independently and differently at the terminal level. The present results also indicate that in cerebral perivascular nerves, the combination of nitric oxide (NO) and acetylcholine (ACh), as well as the combination of NO and VIP, are localized in the same nerve with different axons containing either NO plus ACh, or NO plus VIP. These findings support the hypothesis that ACh and VIP may act as modulators in regulating presynaptic release of NO, and therefore, cerebral neurogenic vasodilation, from their respective perivascular cholinergic-nitric oxidergic and VIPergic-nitric oxidergic nerves.
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PMID:Segregation of VIPergic-nitric oxidergic and cholinergic-nitric oxidergic innervation in porcine middle cerebral arteries. 972 90

Nitric oxide (NO) has been proposed to function as an inhibitory neurotransmitter in the lower urinary tract. This study investigates the distribution of NO-containing neurons and its changes following urethral obstruction in the guinea-pig. By using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and NO synthase (NOS) immunohistochemistry, the highest frequency of NO-containing neurons was observed in the bladder base. Double labelling studies showed that 70.9% of NADPH-d reactive neurons co-expressed NOS immunoreactivity. Acetylcholinesterase reactivity was present in the majority of the intramural neurons with 54% of them expressed NOS immunoreactivity. NADPH-d reactivity was colocalized with vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P immunoreactivities in both neurons and fibres. Colocalization study also revealed that NADPH-d reactive neurons formed a distinct cell population from tyrosine hydroxylase positive neurons. At 12 hours after urethral obstruction, NADPH-d reactivity in the intramural ganglion cells was noticeably enhanced and this was sustained till 24 hours whence some intensely stained neurons appeared to undergo degenerative changes. Neuronal degeneration was more drastic at 48 hours so that the number of NADPH-d positive neurons was significantly reduced. The present study suggests that NO is an important neurotransmitter in the urinary bladder and that it may be involved in the relaxation activity in the bladder base during micturition. It is speculated that the increased NADPH-d reactivity in intramural ganglion cells elicited by urethral obstruction may be responsible for the cell death. It is suggested that the resulting cell loss or bladder denervation may account for the urinary dysfunction such as frequency and urgency of micturition in patients with urethral obstruction.
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PMID:Nitric oxide synthase--its distribution and alteration in the intramural ganglia of the urinary bladder in normal and urethra-obstructed guinea pigs. 1037 26

We have studied the effects of dietary depletion of vitamin E and selenium on endogenous ubiquinone-dependent antioxidant system. Deficiency induced an increase in both coenzyme Q9 and Q10 in liver tissue, reaching a maximum between 4 and 7 weeks of deficient diet consumption. Cytochrome b5 reductase polypeptide was also enriched in membranes after 5 weeks of deficient diet consumption. Substantial DT-diaphorase activity was found in deficient, but not in control plasma membranes. Deficient membranes were very sensitive to lipid peroxidation, although a great protection was observed after incubation with NAD(P)H. Our results show that liver cells can boost endogenous ubiquinone-dependent protective mechanisms in response to deficiency in vitamin E and selenium.
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PMID:Protective role of ubiquinone in vitamin E and selenium-deficient plasma membranes. 1041 28

Succinate dehydrogenase (SDH) participates in the mitochondrial electron transport chain by oxidizing succinate to fumarate and transferring the electrons to ubiquinone. In yeast, it is composed of a catalytic dimer, comprising the Sdh1p and Sdh2p subunits, and a membrane domain, comprising two smaller hydrophobic subunits, Sdh3p and Sdh4p, which anchor the enzyme to the mitochondrial inner membrane. To investigate the role of the Sdh3p anchor polypeptide in enzyme assembly and catalysis, we isolated and characterized seven mutations in the SDH3 gene. Two mutations are premature truncations of Sdh3p with losses of one or three transmembrane segments. The remaining five are missense mutations that are clustered between amino acids 103 and 117, which are proposed to be located in transmembrane segment II or the matrix-localized loop connecting segments II and III. Three mutations, F103V, H113Q, and W116R, strongly but specifically impair quinone reductase activities but have only minor effects on enzyme assembly. The clustering of the mutations strongly suggests that a ubiquinone-binding site is associated with this region of Sdh3p. In addition, the biphasic inhibition of quinone reductase activity by a dinitrophenol inhibitor supports the hypothesis that two distinct quinone-binding sites are present in the yeast SDH.
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PMID:The Saccharomyces cerevisiae succinate-ubiquinone oxidoreductase. Identification of Sdh3p amino acid residues involved in ubiquinone binding. 1044 63


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