Nitric oxide synthase enzymes

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... 

Enzymes Nitric Oxide Synthase and Heme Oxygenase... 

Enzymes Nitric Oxide Synthase and Heme Oxygenase Thomas L. Poulos, Huiying Li,... 

The role of arginase in some cells is not to produce urea but to regulate the concentration of arginine. This is important since arginine is the substrate for the reaction that produces an important messenger molecule, nitric oxide, via the enzyme nitric oxide synthase. 

As discussed in Chapter 22, the activity of gnanyl cyclase is regulated by the messenger nitric oxide this gas stimulates the activity of this enzyme. Nitric oxide is generated from arginine catalysed by the enzyme nitric oxide synthase (NOS) (Figure 19.16). 

STRUCTURES OF GAS-GENERATING HEME ENZYMES NITRIC OXIDE SYNTHASE AND HEME OXYGENASE... 

The gaseous free radical nitric oxide (NO), a non-conventional neural messenger, is synthesized in neurons by the enzyme nitric oxide synthase (NOS), which can be revealed in histological sections by NADPH-diaphorase histochemistry or NOS immunohisto-chemistry. The role of NO in neural signaling has raised considerable interest (see, for example, Schmidt and Walter, 1994), stemming also from the finding that NOS has a discrete distribution in subsets of brain neurons, including intense expression in neuronal subsets of the striatum (Vincent, 2000). 

The enzyme nitric oxide synthase (NOS), that produces NO and citrullin from arginine, occurs as several isoenzymes (Knowles et al., 1989). Type I NOS is a constitutive, calcium and calmodulin-dependent enzyme, present in neurons and, possibly, in glia. Type II NOS is calcium-independent and can be induced in macrophages and glial cells by exposure to bacterial lipopolysaccharide (Galea et al., 1992 Murphy et al., 1993). Type III NOS is the endothelial iso-enzyme. NOS-I, II and III are produced by diflferent genes (Bredt et al., 1991 Lamas et al., 1992 Xie et al., 1992 Lowenstein et al., 1992 Lyons et al. 1992 Ogura et al., 1993). NOS displays NADPH-dependent diaphorase... 

Oxidation of L-arginine by a strain of Nocardia sp. produces nitric oxide and L-citrulline (Chen and Rosazza 1995). The enzyme (nitric oxide synthase) carries out two distinct reactions (1) hydroxylation of L-arginine catalyzed by an enzyme analogous to cytochrome P-450 and (2) a one-electron oxidation of Na -hydroxy-L-arginine to NO and L-citrulline. 

The production of NO in vascular endothelium as well as in other cell types is catalyzed by the enzyme nitric oxide synthase (NOS). Three different classes of NOS have been described through cloning techniques and other approaches (1) an endothelial form of NOS whose activity is stimulated by the binding of the Ca2+-calmodulin complex upon cellular activation of Ca2+ mobilization (2) a neural form of NOS whose activation is through a similar mechanism (i.e., intracellular Ca2+ mobilization) but whose properties are distinct from the endothelial enzyme and (3) an in-... 

NO, derived from L-arginine (L-Arg) by the enzyme nitric oxide synthase (NOS), is involved in the regulation of relevant physiological and pathophysiological functions. The mechanisms by which NO exerts its effects include activation of guanylate cyclase, formation of peroxynitrite, apoptosis, and COX regulation [96]. Apoptosis induction mediated by NO involves mitochondrial depolarization and is blocked by Bcl-2 overexpression [97]. 

An additional group of oxygen-containing radicals, termed RNOS, contain nitrogen as well as oxygen. These are derived principally from the free radical nitric oxide (NO), which is produced endogenously by the enzyme nitric oxide synthase. Nitric oxide combines with O2 or superoxide to produce additional RNOS. 

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