Substrate Binding and Calmodulin Binding to Endothelial Nitric Oxide Synthase Coregulate Its Enzymatic Activity

Nitric Oxide ◽  
1997 ◽  
Vol 1 (1) ◽  
pp. 74-87 ◽  
Author(s):  
Anthony Presta ◽  
Jianwei Liu ◽  
William C. Sessa ◽  
Dennis J. Stuehr
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Enzymatic Activity ◽  
Endothelial Nitric Oxide Synthase ◽  
Substrate Binding ◽  
Calmodulin Binding ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

scholarly journals Endothelial nitric oxide synthase activation and nitric oxide function: new light through old windows

2011 ◽  
Vol 210 (3) ◽  
pp. 239-241 ◽  
Author(s):  
Ian M Bird
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Endothelial Nitric Oxide Synthase ◽  
Vascular Function ◽  
Calmodulin Binding ◽  
And Function ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide ◽  
First Time ◽  
New Evidence

The principle mechanisms operating at the level of endothelial nitric oxide synthase (eNOS) itself to control its activity are phosphorylation, the auto-regulatory properties of the protein itself, and Ca2+/calmodulin binding. It is now clear that activation of eNOS is greatest when phosphorylation of certain serine and threonine residues is accompanied by elevation of cytosolic [Ca2+]i. While eNOS also contains an autoinhibitory loop, Rafikov et al. (2011) present the evidence for a newly identified ‘flexible arm’ that operates in response to redox state. Boeldt et al. (2011) also review the evidence that changes in the nature of endothelial Ca2+ signaling itself in different physiologic states can extend both the amplitude and duration of NO output, and a failure to change these responses in pregnancy is associated with preeclampsia. The change in Ca2+ signaling is mediated through altering capacitative entry mechanisms inherent in the cell, and so many agonist responses using this mechanism are altered. The term ‘adaptive cell signaling’ is also introduced for the first time to describe this phenomenon. Finally NO is classically regarded as a regulator of vascular function, but NO has other actions. One proposed role is regulation of steroid biosynthesis but the physiologic relevance was unclear. Ducsay & Myers (2011) now present new evidence that NO may provide the adrenal with a mechanism to regulate cortisol output according to exposure to hypoxia. One thing all three of these reviews show is that even after several decades of study into NO biosynthesis and function, there are clearly still many things left to discover.

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.

Localization of endothelial nitric oxide synthase in the normal and failing human atrial myocardium

1996 ◽  
Vol 54 ◽  
pp. 786-787
Author(s):  
Chi-Ming Wei ◽  
Margarita Bracamonte ◽  
Shi-Wen Jiang ◽  
Richard C. Daly ◽  
Christopher G.A. McGregor ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Heart Failure ◽  
Nitric Oxide Synthase ◽  
Endothelial Nitric Oxide Synthase ◽  
Cardiac Tissues ◽  
Mammalian Tissues ◽  
End Stage Heart Failure ◽  
End Stage ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Nitric oxide (NO) is a potent endothelium-derived relaxing factor which also may modulate cardiomyocyte inotropism and growth via increasing cGMP. While endothelial nitric oxide synthase (eNOS) isoforms have been detected in non-human mammalian tissues, expression and localization of eNOS in the normal and failing human myocardium are poorly defined. Therefore, the present study was designed to investigate eNOS in human cardiac tissues in the presence and absence of congestive heart failure (CHF).Normal and failing atrial tissue were obtained from six cardiac donors and six end-stage heart failure patients undergoing primary cardiac transplantation. ENOS protein expression and localization was investigated utilizing Western blot analysis and immunohistochemical staining with the polyclonal rabbit antibody to eNOS (Transduction Laboratories, Lexington, Kentucky).

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