NO-synthase



NO-synthases (NOS) catalyze the oxidation of  L -arginine to NO · and L -citrulline to form the intermediate metabolite Nω-hydroxy- L - arginine. The synthesis is influenced by a number of cofactors such as tetrahydropterin (BH 4 ), flavin mononucleotide (FMN), flavindinucleotide (FAD), reduced thiols, endogenous NOS inhibitor - asymmetric dimethylarginine (ADMA) and substrate availability. In addition, the activity of NOS I and III depends on the presence of a calmodulin complex with Ca 2+ (CaM-Ca 2+ ).

The effect of NO · in a given biological system depends on its concentration, diffusibility and concentration of other bioreactants ( superoxide dismutase, catalase , xanthine oxidase , guanylate cyclase, SH-groups, OH-groups, reactive oxygen species , hemoglobin). The resulting NO · can thus gain an electron to form a nitroxyl anion (NO - ) or, conversely, lose an electron to form NO + (nitrosonium ion). Both nitroxyl and nitrosonium ions then react with other molecules or radicals. The immediate metabolite of NO · in blood plasma is nitrite (NO 2- ), which enters erythrocytes and oxidizes to nitrate (NO 3-). Another way is to interact with the superoxide anion O 2 2- · to form peroxynitrite (ONOO - ). It then oxidizes thiols or thioethers, or reacts with polypeptide tyrosine, guanosine, degrades carbohydrates, induces lipid peroxidation, and cleaves DNA. These processes play a key role, for example, in vascular endothelial dysfunction

Source

 * MASOPUST, Jaroslav, et al. Cell pathobiochemistry. 1st edition. Prague: Charles University, 2nd Faculty of Medicine, 2003. 344 pp. 88–92.  ISBN 80-239-1011-6.
 * MASOPUST, Jaroslav, et al. Cell pathobiochemistry. 1st edition. Prague: Charles University, 2nd Faculty of Medicine, 2003. 344 pp. 88–92.  ISBN 80-239-1011-6.