Endothelial nitric oxide synthase eNOS

Three isoforms of NO synthesizing enzymes ( nitric oxide synthase (NOS)) were isolated, purified, and cloned neuronal NO synthase ( neuronal nitric oxide synthase (nNOS) or isoform (I), immunological or inducible NOS ( inducible (immunological) nitric oxide synthase (iNOS) or isoform (II), and endothelial NOS ( endothelial nitric oxide synthase (eNOS) or isoform... 

Endothelial Nitric Oxide Synthase (eNOS) Endothelin Converting Enzyme Endothelins Endothelium... 

FIGURE 34-5 Induction of endothelial nitric oxide synthase (eNOS) in medial thalamus of thiamine-deficient rats. (A) Increased eNOS mRNA. (B) Increased eNOS immunolabeling of vascular endothelial cells (magnification x200). 

Besides cholesterol efflux from arterial wall and its role in RCT, additional properties of HDL have been proposed for its protective anti-atherogenic activities. HDL protects vascular function by a number of potential alternative mechanisms, including inhibition of LDL oxidation [8,9], platelet aggregation and coagulation [10], and endothelial monocyte adhesion [11], as well as promotion of endothelial nitric oxide synthase (eNOS) [12], and prostacyclin synthesis [13-15]. The proposed alternate protective mechanisms for HDL are attractive but many of them lack validation under in vivo conditions. 

A. Blair, P. W. Shaul, I. S. Yuhanna, P. A. Conrad, and E. J. Smart. Oxidized low density lipoprotein displaces endothelial nitric-oxide synthase (eNOS) from plasmalemmal caveolae and impairs eNOS activation. J. Biol. Chem. 274 32512-32519 (1999). 

Takahashi S, Mendelsohn ME. 2003. Synergistic activation of endothelial nitric-oxide synthase (eNOS) by HSP90 and Akt calcium-independent eNOS activation involves formation of an HSP90-Akt-CaM-bound eNOS complex. J Biol Chem 278 30821— 30827. 

After identification, the next step was to determine how NO was made in the endothelium. As with other bodily substances, NO manufacture involves a pathway that requires other chemical entities. The substrate, or raw material required, is an amino acid (a building block of protein), called L-arginine, henceforth in this book simply arginine. A special enzyme, endothelial nitric oxide synthase (eNOS), must be present for NO to be fabricated from... 

Abernethy DR, Babaoglu MO. Polymorphic variant of endothelial nitric oxide synthase (eNOS) markedly impairs endothelium-dependent vascular relaxation [abstract]. Clin Pharmacol Ther 2000 67 141. 

J. P. Gratton, J. Fontana, D. S. O Connor, G. Garcia-Cardena, T. J. McCabe and W. C. Sessa, Reconstitution of an endothelial nitric-oxide synthase (eNOS), hsp90, and caveolin-1 complex in vitro. Evidence that hsp90 facilitates calmodulin stimulated displacement of eNOS from caveolin-1. J Biol Chem 275,22268-22272 (2000). 

The body has three different tissue-specific isoforms of NO synthase, each encoded by a different gene neuronal nitric oxide synthase (nNOS, isoform I), inducible nitric oxide synthase (iNOS, isoform II), and endothelial nitric oxide synthase (eNOS, isoform III). nNOS and eNOS are tightly regulated by Ca concentration to produce the small amounts of NO required for its role as a neurotransmitter and hormone. In contrast, iNOS is present in many cells of the immune system and cell types with a similar lineage, such as macrophages and... 

O2. Endothelial nitric oxide synthase (eNOS) also produces O2 but production of O2 vs. NO is determined by the amount of fully reduced tetrahydrobiopterin (BH4) available, with BH4 suppressing 02 in favor of NO. On a cautionary note, 02 production by many systems may represent a non-physiological activity expressed only when native activity is compromised in some way. 

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