Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.99.1 (NADPH-diaphorase)
 3,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d) positive cells were demonstrated in the medulla of the rat and chick thymus at light microscopic level. The NADPH-d positive cells were present as clusters and were predominantly localized near the corticomedullary boundary. These clusters were closely associated with the thymic cysts. Some cells were seen in close proximity to blood vessels. The presence of nitric oxide (NO) as indicated by the positive NADPH-d reaction in the cells forming the wall of the thymic cyst suggests a modulatory influence of NO over the activities of these cells. Other possible functions of NO are also discussed.
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PMID:NADPH-diaphorase positive cells in the chick and rat thymus. 751 99

A study has been made of the distribution of nitric oxide synthase (NOS) in the developing avian ciliary ganglion. Nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity first appeared in ciliary neurones at embryonic day 10 (E10). The number of NADPH-d positive neurones appeared maximal at this age and thereafter declined; at post hatched day 4 (P4) these neurones were found predominately in the periphery of the ganglion. At the light microscope level the NADPH-d stain appeared throughout the cell soma of the ciliary neurones. This was confirmed using tissue culture techniques. Ultrastructural delineation of horseradish peroxidase-labelled NOS antibodies was also found in the calyx where it was bound to the membranes of the endoplasmic reticulum as well as to the outer membranes of mitochondria. This distribution of NOS in the soma and calyx is consistent with the physiological role of NO as a co-transmitter and retrograde messenger that regulates the quantal secretion of the principal transmitter, acetylcholine, from the calyx.
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PMID:Location of nitric oxide synthase in the developing avian ciliary ganglion. 753 72

Portal hypertension (PHT) is characterized by splanchnic hyperemia caused by a reduction in mesenteric vascular resistance. Mediators of this hyperemia include nitric oxide (NO). This is based on several reports indicating a marked splanchnic hyporesponsiveness in PHT to vaso-constrictor stimuli, both in vitro and in vivo, and a subsequent reversal using specific inhibitors of NO synthase (NOS). The objective of this study was to determine directly if the generation of NO is altered in PHT vasculature. Thus, we compared NOS activity in the hyperemic vasculature of normal rabbits and rabbits with PHT (after undergoing partial portal vein ligation). Nicotinamide adenine dinucleotide phosphate diaphorase staining indicated the presence of NOS within the vascular endothelium. Ca(2+)-dependent NOS activity was significantly increased (P < .05) in PHT particulate fractions from the superior mesenteric artery and thoracic aorta, but not from the portal vein. There was no change in NOS activity within the cytosolic fractions. Arterial wall cyclic guanosine monophosphate (cGMP) levels and plasma nitrite levels were both significantly increased in PHT. These results show enhanced NOS activity in PHT hyperemic vessels concurrent with increased tissue cGMP levels. We conclude that enhanced NO synthesis contributes to the hyperdynamic circulation of PHT.
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PMID:Enhanced nitric oxide synthase activity in portal hypertensive rabbits. 754 37

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d)-stained profiles were evaluated throughout the human hippocampal formation (i.e., dentate gyrus, Ammon's horn, subicular complex, entorhinal cortex) and perirhinal cortex. NADPH-d staining revealed pleomorphic cells, fibers, and blood vessels. Within the entorhinal and the perirhinal cortices, darkly stained (type 1) NADPH-d pyramidal, fusiform, bipolar, and multipolar neurons with extensive dendrites were scattered mainly within deep layers and subjacent white matter. Moderately stained (type 2) NADPH-d round or oval neurons were seen mainly in layers II and III of the entorhinal and perirhinal cortices, in the dentate gyrus polymorphic layer, in the CA fields stratum pyramidal and radiatum, and in the subicular complex. The distribution of type 2 cells was more abundant in the perirhinal cortex compared to the hippocampal formation. Lightly stained (type 3) NADPH-d pyramidal and oval neurons were distributed in CA4, the entorhinal cortex medial subfields, and the amygdalohippocampal transition area. Sections concurrently stained for NADPH-d and nitric oxide synthase (NOS) revealed that all type 1 neurons coexpressed NOS, whereas types 2 and 3 were NOS immunonegative. NADPH-d fibers were heterogeneously distributed within the different regions examined and were frequently in close apposition to reactive blood vessels. The greatest concentration of fibers was in layers III and V-VI of the entorhinal and perirhinal cortices, dentate gyrus polymorphic and molecular layers, and CA1 and CA4. A band of fibers coursing within CA1 divided into dorsal and ventral bundles to reach the presubiculum and entorhinal cortex, respectively. Although the distribution of NADPH-d fibers was conserved across all ages examined (28-98 years), we observed an increase in the density of fiber staining in the aged cases. These results may be relevant to our understanding of selective vulnerability of neuronal systems within the human hippocampal formation in aging and in neurodegenerative diseases.
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PMID:Reduced nicotinamide adenine dinucleotide phosphate-diaphorase/nitric oxide synthase profiles in the human hippocampal formation and perirhinal cortex. 756 Feb 97

Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic and neoplastic effects of free radicals and reactive oxygen species arising from one-electron reductions. These two-electron reductions participate in the reductive bioactivation of cancer chemotherapeutic agents such as mitomycin C in tumor cells. Thus, surprisingly, the same enzymatic reaction that protects normal cells activates cytotoxic drugs used in cancer chemotherapy. The 2.1-A crystal structure of rat liver quinone reductase reveals that the folding of a portion of each monomer is similar to that of flavodoxin, a bacterial FMN-containing protein. Two additional portions of the polypeptide chains are involved in dimerization and in formation of the two identical catalytic sites to which both monomers contribute. The crystallographic structures of two FAD-containing enzyme complexes (one containing NADP+, the other containing duroquinone) suggest that direct hydride transfers from NAD(P)H to FAD and from FADH2 to the quinone [which occupies the site vacated by NAD(P)H] provide a simple rationale for the obligatory two-electron reductions involving a ping-pong mechanism.
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PMID:The three-dimensional structure of NAD(P)H:quinone reductase, a flavoprotein involved in cancer chemoprotection and chemotherapy: mechanism of the two-electron reduction. 756 29

An 8.9-kb segment with hydrogenase genes from the cyanobacterium Anabaena variabilis has been cloned and sequenced. The sequences show homology to the methyl-viologen-reducing hydrogenases from archaebacteria and, even more striking, to the NAD(+)-reducing enzymes from Alcaligenes eutrophus and Nocardia opaca as well as to the NADP(+)-dependent protein from Desulfovibrio fructosovorans. The cluster from A. variabilis contains genes coding for both the hydrogenase heterodimer (hoxH and hoxY) and for the diaphorase moiety (hoxU and hoxF) described for the A. eutrophus enzyme. In A. variabilis the gene cluster is split by two open reading frames (between hoxY and hoxH and between hoxU and hoxY, respectively), and a probably non-coding 0.9-kb segment in an unusual way. The hoxH partial sequence from Anabaena 7119 and Anacystis nidulans was amplified by PCR. Using the labeled segment from A. 7119 as probe, Southern analysis revealed homologous gene segments in the cyanobacteria A. 7119, Anabaena cylindrica, Anacystis nidulans and A. variabilis. The bidirectional hydrogenase from A. nidulans was purified and digests were sequenced. The amino acid sequences obtained showed partial identities to the amino acid sequences deduced from the DNA data of the 8.9-kb segment from A. variabilis. Therefore the 8.9-kb segment contains the genes coding for the bidirectional, reversible hydrogenase from cyanobacteria. Crude extracts from A. nidulans perform NAD(P)H-dependent H2 evolution corroborating the molecular biological demonstration of the NAD(P)(+)-dependent hydrogenase in cyanobacteria.
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PMID:Molecular biological analysis of a bidirectional hydrogenase from cyanobacteria. 758 54

A kinetic study is made of a system consisting of a specific enzymic cycling assay coupled to an enzymic reaction. A kinetic analysis of this system is presented, and the accumulation of chromophore involved in the cycle is seen to be parabolic, i.e. the rate of the reaction increases continuously with constant acceleration. The system is illustrated by the measurement of alkaline phosphatase activity using beta-NADP+ as substrate. The enzymes alcohol dehydrogenase and diaphorase are used to cycle beta-NAD+ in the presence of ethanol and p-Iodonitrotetrazolium Violet. During each turn of the cycle, one molecule of the tetrazolium salt is reduced to an intensely coloured formazan. A simple procedure for evaluating the kinetic parameters involved in the system and for optimizing this cycling assay is described. The method is applicable to the measurement of any enzyme, and its amplification capacity as well as the simplicity of determining kinetic parameters enable it to be employed in enzyme immunoassays to increase the magnitude of the measured response.
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PMID:Kinetic study of an enzymic cycling system coupled to an enzymic step: determination of alkaline phosphatase activity. 761 54

Bovine leukemia virus-transformed lamb embryo fibroblasts (line FLK) possess activity of DT-diaphorase of ca. 260 U/mg protein and similar levels of other NADP(H)-oxidizing enzymes: NADH:oxidase, 359 U/mg; NADPH:oxidase, 43 U/mg; NADH:cytochrome-c reductase, 141 U/mg; NADPH:cytochrome-c reductase, 43 U/mg. In general, the toxicity of aromatic nitrocompounds towards FLK cells increases on increase of single-electron reduction potentials (E1(1)) of nitrocompounds or the log of their reduction rate constants by single-electron-transferring enzymes, microsomal NADPH:cytochrome P-450 reductase (EC 1.6.2.4) and mitochondrial NADH:ubiquinone reductase (EC 1.6.99.3). No correlation between the toxicity and reduction rate of nitrocompounds by rat liver DT-diaphorase (EC 1.6.99.2) was observed. The toxicity is not significantly affected by dicumarol, an inhibitor of DT-diaphorase. Nitrocompounds examined were poor substrates for DT-diaphorase, being 10(4) times less active than menadione. Their poor reactivity is most probably determined by their preferential binding to a NADPH binding site, but not to menadione binding site of diaphorase. These data indicate that at comparable activities of DT-diaphorase and single-electron-transferring NAD(P)H dehydrogenases in the cell, the toxicity of nitrocompounds will be determined mainly by their single-electron reduction reactions.
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PMID:The toxicity of aromatic nitrocompounds to bovine leukemia virus-transformed fibroblasts: the role of single-electron reduction. 766 3

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

Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry was used to study the morphology of labeled axonal plexuses in the human lateral temporal cortex. Strongly stained non-pyramidal neurons and a dense NADPH diaphorase-positive network of fibers were observed in all cortical layers. Certain stained fibers are found to give rise to basket-like formations. Notably other fibers seem to innervate small blood vessels. In addition, numerous blood vessels show a punctate labeling over their surfaces. These findings provide new morphological and chemical details of the axonal innervation of the human neocortex.
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PMID:A study of NADPH diaphorase-positive axonal plexuses in the human temporal cortex. 768 14


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