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)

Nitric oxide synthase is the biosynthetic enzyme for the free radical neurotransmitter nitric oxide. Using an affinity-purified antiserum, nitric oxide synthase was found to be localized to peripheral ocular nerve fibers, related cranial ganglia, and the retina of the rat. In the eye, nitric oxide synthase-like immunoreactive peripheral nerve fibers were visualized mainly in the choroid and about limbal blood vessels. The anterior uvea was quite sparsely innervated, and the cornea was negative. Many principal neurons in the pterygopalatine ganglion were immunoreactive for nitric oxide synthase while very few cells stained in the superior cervical and trigeminal ganglia. Virtually all nitric oxide synthase-like immunoreactive pterygopalatine cells were also immunostained for vasoactive intestinal polypeptide; nitric oxide synthase also partially co-localized with neuropeptide Y in some of the neurons of this ganglion. Pterygopalatine ganglionectomy significantly reduced the number of peripheral nitric oxide synthase-like immunoreactive nerve fibers in the eye. A variety of immunoreactive retinal cells were seen. Most cells in the inner nuclear layer or ganglion cell layer corresponded morphologically to amacrine cells and displaced amacrine cells. Interplexiform cells and occasional faintly stained cells in the outer portion of the inner nuclear layer also were visualized. Nicotinamide adenine dinucleotide phosphate diaphorase histochemistry generally stained cells of similar distribution but did reveal somewhat more extensive localizations in peripheral ocular tissues, the ciliary ganglion, and the retina, compared with nitric oxide synthase immunohistochemistry. Nitric oxide synthase thus localizes to peripheral ocular nerve fibers, chiefly parasympathetic in nature and derived from the pterygopalatine ganglion, and to several cell types in the retina. Nitric oxide probably acts as a choroidal vasodilator of parasympathetic origin in the eye; the neuropeptide co-localizations in the pterygopalatine ganglion suggest complex neuromodulatory interactions. The retinal localizations imply potential neurotransmitter functions for nitric oxide in this tissue.
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PMID:The localization of nitric oxide synthase in the rat eye and related cranial ganglia. 768 60

The distribution of nitric oxide synthase (NOS), an enzyme involved in the synthesis of the presumed non-adrenergic noncholinergic inhibitory neurotransmitter nitric oxide (NO), was demonstrated in the enteric nervous system of the porcine caecum, colon and rectum. Techniques used were NOS-immunocytochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)-histochemistry. Throughout the entire large intestine, NOS-immunoreactive (IR) and NADPHd-positive neurons were abundant in the myenteric and outer submucous plexus. In the inner submucous plexus, only a small number of positive neurons were found in the caecum and colon, while a moderate number was observed in the rectum. The nitrergic neurons in the porcine enteric nerve plexuses were of a range of sizes and shapes, with a small proportion showing immunostaining for vasoactive intestinal polypeptide. Varicose and non-varicose NOS-IR and NADPHd-positive nerve fibres were present in the ganglia and connecting strands of all three plexuses. Nerve fibres were also numerous in the circular muscle layer, scarce in the longitudinal muscle coat and negligible in the mucosal region. The abundance of NOS/NADPHd in the intrinsic innervation of the caecum, colon and rectum of the pig implicates NO as an important neuronal messenger in these regions of the gastrointestinal tract.
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PMID:Distribution and morphological features of nitrergic neurons in the porcine large intestine. 769 26

The Na(+)-translocating NADH-quinone reductase purified from the marine bacterium Vibrio alginolyticus is composed of three subunits, alpha, beta and gamma. From the N-terminal amino acid sequences of each subunit and its polypeptide fragment obtained by partial digestion with V8 protease, oligonucleotides corresponding to forward and reverse primers for each gene (NQR A, B and C) encoding the alpha, beta and gamma subunit, respectively, were synthesized. Using these primers, a part of each gene was amplified from the chromosomal DNA of V. alginolyticus by a PCR method, and the PCR products were used for the cloning of the NQR gene in lambda phage. Among the subclones selected by probe C, the expression of the beta-subunit as a gene product was detected in Escherichia coli membranes by activity staining and Western blotting.
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PMID:Cloning of the Na(+)-translocating NADH-quinone reductase gene from the marine bacterium Vibrio alginolyticus and the expression of the beta-subunit in Escherichia coli. 780 66

Enzyme histochemistry, in combination with immunohistochemistry was used to establish the neurochemistry of neurons in the vas deferens and pelvic ganglia of the guinea-pig. Nerve fibres characterised by reactivity for reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity formed a dense network in the lamina propria and circular muscle layer of the vas deferens, but were very sparse in the longitudinal muscle layer of the vas deferens. NADPH-diaphorase reactivity was also present in nerve fibres forming a dense perivascular plexus in many of the arteries in the pelvic region and in some of the endothelial cells, especially near the origin of the capillaries. Nerves with vasoactive intestinal polypeptide (VIP)-immunoreactivity had a similar distribution to NADPH-diaphorase reactive nerves. Tyrosine hydroxylase (TH)-immunoreactive nerve fibres were found in both muscle layers of the vas deferens. There was no coexistence of VIP- and TH-immunoreactivities in nerve fibres in the vas deferens. In the anterior pelvic ganglia, the origin of the nerve fibres in the vas deferens, several classes of neurons could be identified by the presence or absence of the reactivity for NADPH-diaphorase and immunoreactivity for VIP and TH. Neurons containing both VIP and NADPH-diaphorase reactivity accounted for 40% of neurons in the ganglia. Neurons with VIP-immunoreactivity but not NADPH-diaphorase reactivity accounted for 6%. TH-immunoreactive neurons accounted for 22% of neurons in the anterior pelvic ganglia. Very rare cells (< 1%) contained both VIP- and TH-immunoreactivities. The remaining neurons, which were not labelled by any of these markers, comprised 31% of neurons in anterior pelvic ganglia. These results demonstrate the existence of NADPH-diaphorase reactivity in neurons containing VIP-immunoreactivity, thus suggest that nitric oxide may be a neurotransmitter in guinea-pig vas deferens, especially in the circular muscle layer, in the arteries, and in other pelvic organs innervated by pelvic ganglia.
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PMID:NADPH-diaphorase and other neuronal markers in nerves and ganglia supplying the guinea-pig vas deferens. 791 4

In cat middle cerebral arterial strips denuded of the endothelium, nicotine produced a relaxation that was abolished by treatment with hexamethonium. The relaxation was partially inhibited by treatment with NG-nitro-L-arginine (L-NNA), a nitric oxide (NO) synthase inhibitor, and oxyhemoglobin, an NO scavenger. The remaining relaxation in the media containing L-NNA was abolished in the strips made unresponsive to calcitonin gene-related peptide (CGRP) by its repeated application. However, this was not the case when the strips were made tachyphylaxic to vasoactive intestinal polypeptide. The nicotine-induced relaxation was also partially attenuated by pretreatment with capsaicin; the remaining relaxation was abolished by L-NNA but not by its D-enantiomer. The inhibitory effect of L-NNA was reversed by L- but not D-arginine. Histochemical study revealed that injections of ethanol into the vicinity of pterygopalatine ganglion abolished the positive staining for nicotinamide adenine dinucleotide phosphate diaphorase activity and the CGRP immunoreactivity in perivascular nerves innervating the middle cerebral artery of the ipsilateral side. The nicotine-induced relaxation in the middle cerebral artery from the ethanol-injected side was markedly inhibited compared with that from the nontreated side, whereas the relaxations induced by exogenously applied NO and CGRP were unaffected. We conclude that nicotine stimulates nicotinic receptors in nerve terminals and liberates NO or NO-like substance(s) and CGRP as neurotransmitters in cat middle cerebral arteries.
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PMID:Neurogenic relaxations caused by nicotine in isolated cat middle cerebral arteries. 807 71

The overexpression and purification of recombinant rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase (3 alpha-HSD; EC 1.1.1.50) in Escherichia coli are described. The properties of the homogeneous recombinant 3 alpha-HSD (r3 alpha-HSD) confirm that a single polypeptide can function as a HSD, as a dihydrodiol dehydrogenase, and as an aromatic aldehyde, ketone, and quinone reductase. Cys-170, Cys-242, and Cys-217, implicated by bromoacetoxysteroid affinity-labeling agents as points of contact for the C-3, C-11, and C-17 positions of steroid ligands, were mutated to alanines. Unexpectedly, the homogeneous C170A and C242A mutants were kinetically similar to wild-type r3 alpha-HSD. By contrast, the C217A mutant gave Km values that were 4-fold higher for androstanedione and 2-fold higher for NADH. Inspection of the recently solved crystal structure of rat liver 3 alpha-HSD (Hoog, S. S., Pawlowski, J. E., Alzari, P. M., Penning, T. M., and Lewis, M. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 2517-2521) places Cys-170 and Cys-242 on the periphery of an alpha/beta-barrel so that they cannot be involved in catalysis of steroid recognition. This demonstrates that bromoacetoxysteroid affinity-labeling agents may provide misleading information regarding the topography of steroid hormone binding sites. When NADPH was modeled into the crystal structure of 3 alpha-HSD, Tyr-55 was implicated as the general acid, since it is in close proximity to the C-4 position of the nicotinamide ring and could polarize the substrate carbonyl. In support of this model, the purified Y55F mutant was found to be catalytically inactive, but still formed an E-NADPH complex (measured by fluorescence titration) and an E-NADH-testosterone complex (measured by equilibrium dialysis). The ability of the Y55F mutant to form binary and ternary complexes, but not aid in hydride transfer, is consistent with Tyr-55 acting as the general acid. 3 alpha-HSD is a member of the aldo-keto reductase superfamily, and Tyr-55 is invariant in members of this family where it may perform a similar function. Tyr-205 is present in a pentapeptide sequence that is conserved in HSDs that belong to the short-chain alcohol dehydrogenase family and has been implicated as the general acid within these enzymes. The Y205F mutant was found to be kinetically similar to wild-type r3 alpha-HSD.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Overexpression and mutagenesis of the cDNA for rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase. Role of cysteines and tyrosines in catalysis. 817 84

Folding models suggest that the highly conserved histidine 217 of the cytochrome b subunit from the cytochrome bc1 complex is close to the quinone reductase (Qi) site. This histidine (bH217) in the cytochrome b polypeptide of the photosynthetic bacterium Rhodobacter capsulatus has been replaced with three other residues, aspartate (D), arginine (R), and leucine (L). bH217D and bH217R are able to grow photoheterotrophically and contain active cytochrome bc1 complexes (60% of wild-type activity), whereas the bH217L mutant is photosynthetically incompetent and contains a cytochrome bc1 complex that has only 10% of the wild-type activity. Single-turnover flash-activated electron transfer experiments show that cytochrome bH is reduced via the Qo site with near native rates in the mutant strains but that electron transfer between cytochrome bH and quinone bound at the Qi site is greatly slowed. These results are consistent with redox midpoint potential (Em) measurements of the cytochrome b subunit hemes and the Qi site quinone. The Em values of cyt bL and bH are approximately the same in the mutants and wild type, although the mutant strains have a larger relative concentration of what may be the high-potential form of cytochrome bH, called cytochrome b150. However, the redox properties of the semiquinone at the Qi site are altered significantly. The Qi site semiquinone stability constant of bH217R is 10 times higher than in the wild type, while in the other two strains (bH217D and bH217L) the stability constant is much lower than in the wild type. Thus H217 appears to have major effects on the redox properties of the quinone bound at the Qi site. These data are incorporated into a suggestion that H217 forms part of the binding pocket of the Qi site in a manner reminiscent of the interaction between quinone bound at the Qb site and H190 of the L subunit of the bacterial photosynthetic reaction center.
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PMID:Requirement of histidine 217 for ubiquinone reductase activity (Qi site) in the cytochrome bc1 complex. 829

In our previous papers, seven structural genes (NQO1-7) of the energy-transducing NADH-quinone (Q) oxidoreductase of Paracoccus denitrificans were characterized [Xu, X., Matsuno-Yagi, A., & Yagi, T. (1991a) Biochemistry 30, 8678-8684; (1991b) Biochemistry 30, 6422-6428; (1992a) Biochemistry 31, 6925-6932; (1992b) Arch. Biochem. Biophys. 296, 40-48]. This paper reports the identification, cloning, and sequencing of seven additional structural genes in the same gene cluster (P. denitrificans enzyme complex). These seven genes, designated NQO8-14, are composed of 1038, 492, 603, 306, 2112, 1542, and 1500 base pairs, respectively. The polypeptides encoded by the NQO8-14 genes are homologous, respectively, to the ND1 product, the 23-kDa polypeptide, and the ND6, ND4L, ND5, ND4, and ND2 products of the bovine NADH-Q oxidoreductase. The order of the 14 structural genes of the Paracoccus energy-transducing NADH-Q oxidoreductase in the gene cluster is NQ07, NQO6, NQO5, NQO2, NQO1, NQO3, NQO8, NQO9, NQO10, NQO11, NQO12, NQO13, and NQO14. Downstream from the NQO14 gene an open reading frame (designated URF240) was detected which encodes a predicted polypeptide homologous to the biotin [acetyl-CoA-carboxylase] ligase of Escherichia coli. In addition, a putative terminal sequence motif was observed downstream of the NQO14 gene, suggesting that the structural gene NQO14 is the 3'-terminal gene of the Paracoccus NADH-Q oxidoreductase gene cluster. Nucleotide sequencing of the entire gene cluster revealed the presence of three unidentified reading frames: one between the NQO3 and NQO8 genes and other two between the NQO9 and NQO10 genes. These are designated URF4, URF5, and URF6 and are composed of 768, 393, and 405 base pairs, respectively. The possible functions of the putative proteins encoded by URF5 and URF6 are discussed.
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PMID:DNA sequencing of the seven remaining structural genes of the gene cluster encoding the energy-transducing NADH-quinone oxidoreductase of Paracoccus denitrificans. 842

Using non-denaturing gel electrophoresis and staining with nitro-blue tetrazolium, we reveal the presence of two NAD(P)H oxidoreductase activity bands within thylakoids membranes of Solanum tuberosum L. Second dimension SDS-PAGE and Western analysis show that one of the activity bands contains several polypeptides, two of them being recognized by antibodies directed against peptides corresponding to conserved domains of chloroplastic genes products NDH B and NDH J (at 32 and 18 kDa, respectively). Both activity bands also contain a polypeptide (around 36 kDa) recognized by an antibody directed against ferredoxin-NADP(+)-reductase (FNR). We conclude from these results that both chloroplastic ndh B and ndh J gene products are components of a thylakoid NAD(P)H dehydrogenase complex. The association with FNR is suggested to allow the complex to use NADPH instead of NADH as a preferential substrate.
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PMID:Evidence for an association of ndh B, ndh J gene products and ferredoxin-NADP-reductase as components of a chloroplastic NAD(P)H dehydrogenase complex. 855 17

Nitric oxide (NO) plays an important physiological role in regulating gastrointestinal motility. Involvement of endogenous NO was evaluated in the response to non-adrenergic, non-cholinergic (NANC) nerve stimulation of the dog sphincter muscle of Oddi. Transmural electrical stimulation (TES), nicotine (10(-5) M) and K+ (10 mM) produced only a relaxation in the sphincter muscle strips contracted with substance P, which was not potentiated by atropine. The TES-induced relaxation was abolished by tetrodotoxin (3 x 10(-7) M) and oxyhaemoglobin (1.6 x 10(-5) M), but not affected by atropine (10(-7) M), propranolol (10(-7) M), phentolamine (10(-7) M), indomethacin (10(-6) M), cholecystokinin (CCK, 10(-8) M) and vasoactive intestinal polypeptide (VIP, 10(-8) M). The relaxation was also abolished by treatment with NG-nitro-L-arginine (L-NA, 10(-5) M), an NO synthase inhibitor. Nicotine produced a transient relaxation, which was abolished by tetrodotoxin, hexamethonium (10(-5) M) and L-NA, but not affected by atropine and NG-nitro-D-arginine (D-NA, 10(-5) M). The addition of K+ elicited a transient relaxation, which was abolished by tetrodotoxin and L-NA. The inhibitory effects of L-NA were antagonized by L-arginine (10(-3) M). The presence of neurons containing nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase was histochemically demonstrated in the sphincter of Oddi. These findings may indicate that TES, nicotine and K+ liberate NO from NANC inhibitory nerve which is involved in the relaxation of the dog sphincter of Oddi. The muscular tone does not seem to be regulated by cholinergic nerves under the experimental conditions used.
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PMID:Functional role and histological demonstration of nitric-oxide-mediated inhibitory nerves in dog sphincter of Oddi. 857 10


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