scholarly journals Nitric oxide synthases (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Timothy R. Billiar ◽  
Giuseppe Cirino ◽  
David Fulton ◽  
Roberto Motterlini ◽  
Andreas Papapetropoulos ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electron Flow ◽  
Amino Acid Level ◽  
Nitric Oxide Synthases ◽  
Binding Motif ◽  
Subcellular Targeting ◽  
Intracellular Location ◽  
Calmodulin Binding ◽  
Oxygenase Domain ◽  
Nos Isoforms

Nitric oxide synthases (NOS, E.C. 1.14.13.39) are a family of oxidoreductases that synthesize nitric oxide (NO.) via the NADPH and oxygen-dependent consumption of L-arginine with the resultant by-product, L-citrulline. There are 3 NOS isoforms and they are related by their capacity to produce NO, highly conserved organization of functional domains and significant homology at the amino acid level. NOS isoforms are functionally distinguished by the cell type where they are expressed, intracellular targeting and transcriptional and post-translation mechanisms regulating enzyme activity. The nomenclature suggested by NC-IUPHAR of NOS I, II and III [11] has not gained wide acceptance, and the 3 isoforms are more commonly referred to as neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS) which reflect the location of expression (nNOS and eNOS) and inducible expression (iNOS). All are dimeric enzymes that shuttle electrons from NADPH, which binds to a C-terminal reductase domain, through the flavins FAD and FMN to the oxygenase domain of the other monomer to enable the BH4-dependent reduction of heme bound oxygen for insertion into the substrate, L-arginine. Electron flow from reductase to oxygenase domain is controlled by calmodulin binding to canonical calmodulin binding motif located between these domains. eNOS and nNOS isoforms are activated at concentrations of calcium greater than 100 nM, while iNOS shows higher affinity for Ca2+/calmodulin with great avidity and is essentially calcium-independent and constitutively active. Efficient stimulus-dependent coupling of nNOS and eNOS is achieved via subcellular targeting through respective N-terminal PDZ and fatty acid acylation domains whereas iNOS is largely cytosolic and function is independent of intracellular location. nNOS is primarily expressed in the brain and neuronal tissue, iNOS in immune cells such as macrophages and eNOS in the endothelial layer of the vasculature although exceptions in other cells have been documented. L-NAME and related modified arginine analogues are inhibitors of all three isoforms, with IC50 values in the micromolar range.

Gene and protein expressions of nitric oxide synthases in ischemia-reperfused peripheral nerve of the rat

2001 ◽  
Vol 281 (3) ◽  
pp. C849-C856 ◽  
Author(s):  
Wen-Ning Qi ◽  
Zuo-Qin Yan ◽  
Peter G. Whang ◽  
Qi Zhou ◽  
Long-En Chen ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Peripheral Nerve ◽  
Ischemia Reperfusion ◽  
Nitric Oxide Synthases ◽  
Inos Mrna ◽  
Mrna Levels ◽  
Protein Expressions ◽  
Enos Mrna ◽  
Nos Isoforms ◽  
Endothelial Nitric Oxide

This study examined mRNA and protein expressions of neuronal (nNOS), inducible (iNOS), and endothelial nitric oxide synthases (eNOS) in peripheral nerve after ischemia-reperfusion (I/R). Sixty-six rats were divided into the ischemia only and I/R groups. One sciatic nerve of each animal was used as the experimental side and the opposite untreated nerve as the control. mRNA levels in the nerve were quantitatively measured by competitive PCR, and protein was determined by Western blotting and immunohistochemical staining. The results showed that, after ischemia (2 h), both nNOS and eNOS protein expressions decreased. After I/R (2 h of ischemia followed by 3 h of reperfusion), expression of both nNOS and eNOS mRNA and protein decreased further. In contrast, iNOS mRNA significantly increased after ischemia and was further upregulated (14-fold) after I/R, while iNOS protein was not detected. The results reveal the dynamic expression of individual NOS isoforms during the course of I/R injury. An understanding of this modulation on a cellular and molecular level may lead to understanding the mechanisms of I/R injury and to methods of ameliorating peripheral nerve injury.

scholarly journals The C Termini of Constitutive Nitric-oxide Synthases Control Electron Flow through the Flavin and Heme Domains and Affect Modulation by Calmodulin

2000 ◽  
Vol 275 (38) ◽  
pp. 29225-29232 ◽  
Author(s):  
Linda J. Roman ◽  
Pavel Martásek ◽  
R. Timothy Miller ◽  
Dawn E. Harris ◽  
Melissa A. de la Garza ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electron Flow ◽  
Nitric Oxide Synthases ◽  
Flow Through

scholarly journals Inhibition of mammalian nitric oxide synthases by agmatine, an endogenous polyamine formed by decarboxylation of arginine

1996 ◽  
Vol 316 (1) ◽  
pp. 247-249 ◽  
Author(s):  
Elena GALEA ◽  
S. REGUNATHAN ◽  
Vassily ELIOPOULOS ◽  
Douglas L. FEINSTEIN ◽  
Donald J. REIS
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Enzyme Activity ◽  
Mammalian Cells ◽  
Structural Similarity ◽  
Nitric Oxide Synthases ◽  
No Production ◽  
Brain Macrophages ◽  
Nos Inhibitor ◽  
Nos Isoforms

Agmatine, decarboxylated arginine, is a metabolic product of mammalian cells. Considering the close structural similarity between L-arginine and agmatine, we investigated the interaction of agmatine and nitric oxide synthases (NOSs), which use L-arginine to generate nitric oxide (NO) and citrulline. Brain, macrophages and endothelial cells were respectively used as sources for NOS isoforms I, II and III. Enzyme activity was measured by the production of nitrites or L-citrulline. Agmatine was a competitive NOS inhibitor but not an NO precursor. Ki values were approx. 660 μM (NOS I), 220 μM (NOS II) and 7.5 mM (NOS III). Structurally related polyamines did not inhibit NOS activity. Agmatine, therefore, may be an endogenous regulator of NO production in mammals.

scholarly journals Intra- and inter-molecular effects of a conserved arginine residue of neuronal and inducible nitric oxide synthases on FMN and calmodulin binding

2013 ◽  
Vol 533 (1-2) ◽  
pp. 88-94 ◽  
Author(s):  
Satya Prakash Panda ◽  
Srikanth R. Polusani ◽  
Dean L. Kellogg ◽  
Priya Venkatakrishnan ◽  
Madeline G. Roman ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthases ◽  
Arginine Residue ◽  
Calmodulin Binding ◽  
Molecular Effects ◽  
Inducible Nitric Oxide

Calmodulin-dependent regulation of mammalian nitric oxide synthase

2003 ◽  
Vol 31 (3) ◽  
pp. 502-505 ◽  
Author(s):  
S. Daff
Keyword(s):  
Nitric Oxide ◽  
Amino Acid ◽  
Cell Signalling ◽  
Structural Rearrangement ◽  
Intramolecular Electron Transfer ◽  
C Terminus ◽  
Oxygenase Domain ◽  
Lock In ◽  
Nos Isoforms ◽  
Reductase Domain

The nitric oxide synthases are large, modular, dimeric enzymes composed of a reductase domain, which is related to cytochrome P450 reductase, and a structurally unique oxygenase domain containing a Cys-ligated haem. Both the neuronal and endothelial isoforms are activated by the reversible binding of calmodulin (CaM) at elevated intracellular Ca2+ levels to produce NO as part of a number of cell signalling pathways. CaM binds to the linker region between the two domains and activates the enzyme by inducing intramolecular electron transfer. Protein-engineering experiments have shown that a series of unusual autoinhibitory inserts found only in the CaM-dependent NOS isoforms control both CaM binding and the structural rearrangement it induces. These lie in the reductase domain of the enzyme and include a 40-amino-acid autoinhibitory loop in the FMN-binding module, a 30-amino-acid extension to the C-terminus and the CaM-binding site itself. The substrate (NADPH) also plays an important role in defining the CaM-dependence of the reductase domain by inducing a tight conformational lock in the absence of CaM. Both the substrate and the conformational lock appear to be released on CaM binding; the resultant domain mobility leads to activation.

scholarly journals Superoxide generation by endothelial nitric oxide synthase: The influence of cofactors

1998 ◽  
Vol 95 (16) ◽  
pp. 9220-9225 ◽  
Author(s):  
Jeannette Vásquez-Vivar ◽  
B. Kalyanaraman ◽  
Pavel Martásek ◽  
Neil Hogg ◽  
Bettie Sue Siler Masters ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Endothelial Nitric Oxide Synthase ◽  
Heme Iron ◽  
Superoxide Generation ◽  
Calmodulin Binding ◽  
Resonance Spin ◽  
Oxygenase Domain ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

The mechanism of superoxide generation by endothelial nitric oxide synthase (eNOS) was investigated by the electron spin resonance spin-trapping technique using 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide. In the absence of calcium/calmodulin, eNOS produces low amounts of superoxide. Upon activating eNOS electron transfer reactions by calcium/calmodulin binding, superoxide formation is increased. Heme-iron ligands, cyanide, imidazole, and the phenyl(diazene)-derived radical inhibit superoxide generation. No inhibition is observed after addition of l-arginine, NG-hydroxy-l-arginine, l-thiocitrulline, and l-NG-monomethyl arginine to activated eNOS. These results demonstrate that superoxide is generated from the oxygenase domain by dissociation of the ferrous–dioxygen complex and that occupation of the l-arginine binding site does not inhibit this process. However, the concomitant addition of l-arginine and tetrahydrobiopterin (BH4) abolishes superoxide generation by eNOS. Under these conditions, l-citrulline production is close to maximal. Our data indicate that BH4 fully couples l-arginine oxidation to NADPH consumption and prevents dissociation of the ferrous–dioxygen complex. Under these conditions, eNOS does not generate superoxide. The presence of flavins, at concentrations commonly employed in NOS assay systems, enhances superoxide generation from the reductase domain. Our data indicate that modulation of BH4 concentration may regulate the ratio of superoxide to nitric oxide generated by eNOS.

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