Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.99.1 (NADPH-diaphorase)
 3,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NO synthase (NOS) catalyzes the oxidation of L-arginine to L-citrulline and nitric oxide (NO) or a NO-releasing compound. At least three isoforms of NOS exist (types I-III). The activities of the type I isoform purified from brain and the type III isoform purified from endothelial cells are regulated by the intracellular free calcium concentration ([Ca2+]i) and the Ca(2+)-binding protein calmodulin. At resting [Ca2+]i, both isozymes are inactive; they become fully active at [Ca2+]i greater than or equal to 500 nM Ca2+. Longer lasting increases in [Ca2+]i may downregulate NO formation, for in vitro phosphorylation by Ca2+/calmodulin protein kinase II decreases the Vmax of NOS. Besides the conversion of L-arginine, type I NOS, Ca2+/calmodulin dependently, generates H2O2 and reduces cytochrome c/P450. Other redox activities, i.e. the reduction of nitroblue tetrazolium to diformazan (NADPH-diaphorase) or of quinoid-dihydrobiopterin to tetrahydrobiopterin, by NOS appear to be Ca2+/calmodulin-independent.
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PMID:Ca2+/calmodulin-regulated nitric oxide synthases. 138 Apr 5

The messenger molecule nitric oxide (NO) is involved in blood flow regulation, cytotoxicity, and neural signalling, processes that are important in the physiology and pathophysiology of the mammalian cochlea. However, neither the presence of NO nor its synthetic enzyme, NO synthase, has been established in the peripheral auditory system. NO synthase activity, measured as the enzymatic conversion of radioactive arginine to citrulline, was predominantly soluble in the auditory nerve, lateral wall, vestibule and cochlear neuroepithelium. N-methyl-L-arginine and trifluoperazine inhibited NO synthase activity in the lateral wall and auditory nerve. Histochemical staining by NADPH-diaphorase localized NOS activity to the lateral wall and the neuronal elements of the organ of Corti. Based on these results, the predominant NO synthase isoform in the cochlea is the neuronal type-I isoform.
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PMID:Detection and characterization of nitric oxide synthase in the mammalian cochlea. 753 58