Nitric oxide synthase

The product of agmatine oxidation catalyzed by Pisum sativum L. copper amine oxidase has been identified by means of one- and two-dimensional 1H-NMR spectroscopy to be N-amidino-2-hydroxypyrrolidine. This compound inhibits competitively rat nitric oxide synthase type I and type II (NOS-I and NOS-II, respectively) and bovine trypsin (trypsin) activity, values of Ki being (1.1 ± 0.1) · 10)5 M (at pH 7.5 and 37.0 °C), (2.1 ± 0.1) · 10)5 M (at pH 7.5 and 37.0 °C), and (8.9 ± 0.4) · 10)5 M (at pH 6.8 and 21.0 °C), respectively. ...

9p research12 01-06-2013 32 2   Download

Two neuropeptides have been isolated and identi®ed from the secretions of the skin glands of the Stony Creek Frog Litoria lesueuri. The ®rst of these, the known neuropeptide caerulein 1.1, is a common constituent of anuran skin secretions, and has the sequence pEQY(SO3 )TGWMDF-NH2 . This neuropeptide is smooth muscle active, an anal-gaesic more potent thanmorphine and is also thought to be a hormone.

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Production of nitric oxide (NO) in response to bacterial lipopolysaccharide (LPS) was investigated using cultures of mouse peritoneal exudate cells (PEC) and the macrophage cell line RAW264.7. In the presence of anti-(interferon-c) (IFN-c), NO production was markedly suppressed in the PEC culture but not in the RAW264.7 culture. In the PEC culture, LPS induced both IFN-cproduction and activation of IFNresponse factor-1, which leads to the gene expression of inducible NO synthase, but neither was induced in the culture of RAW264.7 cells....

10p tumor12 20-04-2013 30 4   Download

A large number of bioactive peptides have been isolated from amphibian skin secretions. These peptides have a variety of actions including antibiotic and anticancer acti-vities and the inhibition of neuronal nitric oxide synthase. We have investigated the structure–activity relationship of citropin 1.1, a broad-spectrum antibiotic and anticancer agent that also causes inhibition of neuronal nitric oxide synthase, by making a number of synthetically modified analogues.

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Nitric oxide (NO) is a potent intra- and intercellular mes-senger involved in the control of vascular tone, neuronal signallingandhost response to infection. Inmammals,NOis synthesized by oxidation ofL-arginine catalysed by heme-proteins called NO-synthases with intermediate formation of N x -hydroxy-L-arginine (NOHA). NOHA and some hydroxyguanidines have been shown to be able to deliver nitrogen oxides including NO in the presence of various oxidative systems.

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The binding of several alkyl- and aryl-guanidines andN-hydroxyguanidines to the oxygenase domain of inducible NO-synthase (iNOSoxy) was studied by UV⁄Vis difference spectroscopy. In a very general manner, monosubsti-tuted guanidines exhibited affinities for iNOSoxy that were very close to those of the corresponding N-hydroxyguanidines. The highest affinities were observed for the natural substrates,l-arginine and N x -hydroxy-l-arginine (Kd at thelmlevel).

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Inducible nitric oxide synthase (iNOS) functions as a homodimer. In cell extracts, iNOS molecules partition both in cytosolic and particulate frac-tions, indicating that iNOS exists as soluble and membrane associated forms. In this study, iNOS features were investigated in human intestinal epithelial cells stimulated with cytokines and in duodenum from mice exposed to flagellin. Our experiments indicate that iNOS is mainly associ-ated with the particulate fraction of cell extracts.

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In rat neuronal nitric oxide synthase, Phe1395 is positioned over the FAD isoalloxazine ring. This is replaced by Trp676 in human cytochrome P450 reductase, a tryptophan in related diflavin reductases (e.g. methionine synthase reduc-tase andnovel reductase 1), and tyrosine inplant ferredoxin-NADP + reductase. Trp676 in human cytochrome P450 reductase is conformationallymobile, andplays akey role in enzyme reduction. Mutagenesis of Trp676 to alanine results in a functional NADH-dependent reductase. ...

13p dell39 03-04-2013 39 5   Download

Metallothioneins (MTs) release boundmetalswhen exposed to nitric oxide. At inflammatory sites, both metallothionein and inducible nitric oxide synthase (iNOS) are induced by the same factors and the zinc released from metallothionein by NO suppresses both the induction and activity of iNOS.

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Single turnover reactions of the inducible nitric oxide synthase oxygenase domain (iNOSoxy) in the presence of several nona-amino acid N-hydroxy-guanidines and guanidines were studied by stopped-flow visible spectro-scopy, and compared with reactions using the native substrates l-arginine (l-arg) or N x -hydroxy-l-arginine (NOHA).

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Calmodulin (CaM) is a cytosolic Ca 2+ signal-transducing protein that binds and activates many different cellular enzymes with physiological rele-vance, including the nitric oxide synthase (NOS) isozymes. CaM consists of two globular domains joined by a central linker; each domain contains an EF hand pair.

13p inspiron33 26-03-2013 41 4   Download

Cupiennin 1a (GFGALFKFLAKKVAKTVAKQAAKQGAKYVVNKQ-ME-NH2) is a potent venom component of the spider Cupiennius salei. Cupiennin 1a shows multifaceted activity. In addition to known antimicro-bial and cytolytic properties, cupiennin 1a inhibits the formation of nitric oxide by neuronal nitric oxide synthase at an IC50 concentration of 1.3 ± 0.3lm.

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The existence of an inducible mitochondrial nitric oxide synthase has been recently related to the nitrosative⁄oxidative damage and mitochondrial dys-function that occurs during endotoxemia. Melatonin inhibits both inducible nitric oxide synthase and inducible mitochondrial nitric oxide synthase activities, a finding related to the antiseptic properties of the indoleamine.

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We have shown previously that isolated heat shock protein 90 (HSP90) and nitric oxide synthase (NOS), once associated in a heterocomplex, become completely resistant to calpain digestion. In this study, it is shown that, in vivo, under conditions of calpain activation, the protection of NOS degradation occurs.

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Syntrophins are components of the dystrophin–glycoprotein complex of the plasma membrane in muscular and neuronal cells, and recruit signaling proteins such as neuronal nitric oxide synthase via their multiple protein– protein interaction motifs.

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Ca 2+ loading of Jurkat and bovine aorta endothelium cells induces the degradation of the neuronal and endothelial nitric oxide synthases that are selectively expressed in these cell lines. For neuronal nitric oxide synthase, this process involves a conservative limited proteolysis without appreciable loss of catalytic activity.

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There are many reports of an arginine-dependent nitric oxide synthase activity in plants; however, the gene(s) or protein(s) responsible for this activity have yet to be convincingly identified. To measure nitric oxide syn-thase activity, many studies have relied on a citrulline-based assay that measures the formation ofl-citrulline from l-arginine using ion exchange chromatography.

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During catalysis, the heme in nitric oxide synthase (NOS) binds NO before releasing it to the environment. Oxidation of the NOS ferrous heme–NO complex by O2 is key for catalytic cycling, but the mechanism is unclear. We utilized stopped-flow methods to study the reaction of O2 with ferrous heme–NO complexes of inducible and neuronal NOS enzymes.

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Nitric oxide synthases belong to a family of dual-flavin enzymes that trans-fer electrons from NAD(P)H to a variety of heme protein acceptors. Dur-ing catalysis, their FMN subdomain plays a central role by acting as both an electron acceptor (receiving electrons from FAD) and an electron donor, and is thought to undergo large conformational movements and engage in two distinct protein–protein interactions in the process.

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The temporal aspects of signaling are critical to the function of signals in communications, feedback regulation and control. The production and transduction of biological signals by enzymes comprises an area of central importance and rapid progress in the biomedical sciences.

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