Arginine L-Arg

These substances directly stimulate soluble GC and elevate cGMP levels in platelets. 

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In mammalian cells NO is produced by the oxidation of the terminal guanidino nitrogen of L-arginine (L-arg) by nitric oxide synthase (NOS). According to patent literature, NOS inhibitors have been one of the most intensively investigated research areas in industry of the last couple of years. 

Figure 2 Stoichiometry of the enzymatic mechanism of formation of NO, and the structure of a competitive inhibitor, N -monomethyl-L-arginine (NMMA). NO is synthesized by all NOS s by a similar mechanism, involving the NADPH-dependent mixed-function oxidation of a guanidino nitrogen of the amino acid L-arginine (L-arg) to produce L-citrulline (L-cit) and -NO. The nonintegral stoichiometries are explained in the text. NMMA inhibits NOS as a competitive inhibitor...

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]. 

Recently there has been a widespread interest in thiol antioxidants, glutathione, and related enzymes, hydrogen sulfide, sesame oil components, L-arginine (L-Arg) and other nitric oxide modulators [129]. While the former compounds may have direct antioxidant actions, L-Arg is both a direct precursor of nitric oxide as well as an antioxidant [110]. These compounds may assist in lowering high blood pressure. 

L-Arginine S(+)-2-Amino-5-[(aminoiminomethyl)amino]pentanoic acid (L-arg)... 

A comprehensive, randomized, placebo-controlled trial of infused bolus L-arg and its enantiomer (D-arg) included healthy subjects, non-insulin dependent diabetics, hypertensive subjects, and normotensives with primary hypercholesterolemia [147]. A blood-pressure drop and an acute inhibition of ADP-induced aggregation in platelet-rich plasma were observed in all subjects after L-arg administration (<5 g). Both responses to L-arg infusion closely correlated in magnitude, were weaker in noninsulin dependent diabetics and hypercholesterolemics, and declined with increasing age. Notably, D-arg did not elicit any of the L-arg effects, which were reduced by some 70% when superimposed upon ongoing, nonselective NOS inhibition with infused L-N-monomethyl-arginine (L-NMMA). Since D-arg is not a NOS substrate, and L-NMMA is a substrate-competitive NOS inhibitor, the L-arg effects observed in this study were theorized to reflect a rise in vascular NO production by eNOS. In contrast, the inhibition of platelet aggregation observed in vitro after a 5 min L-arg infusion (160 mg total dose) into healthy subjects and patients with angiographic... 

The crystal structure of kynureninase from P. fluorescens was solved in 2004. The enzyme shares the same structural fold as aspartate aminotransferase, but shares low sequence similarity. An active site arginine residue (Arg-375) was identified, which is important in substrate binding. The structure of the human kynureninase, which shows a catalytic preference for 3-hydroxy-kynurenine over L-kynurenine, was solved in 2007. The human enzyme shares the same fold as the P. fluorescens enzyme, and also contains an active site arginine residue (Arg-434). The catalytic mechanism requires two acid/base residues, which have not yet been unambiguously assigned. The hydrolytic cleavage step is believed to proceed via a general base mechanism. ... 

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