title: Involvement of the perferryl complex of nitric oxide synthase in the catalysis of secondary free radical formation.
abstract: Neuronal nitric oxide synthase (NOS I) has been shown to generate nitric oxide (NO*) and superoxide (O(2)* during enzymatic cycling, and the ratio of each free radical is dependent upon the concentration of L-arginine. Using spin trapping and electron paramagnetic resonance spectroscopy, we detected alpha-hydroxyethyl radical (CH(3)*CHOH), produced during the NOS I metabolism of ethanol (EtOH). The generation of CH(3)*CHOH by NOS I was found to be Ca(2+)/calmodulin dependent. Superoxide dismutase prevented CH(3)*CHOH formation in the absence of L-arginine. However, in the presence of L-arginine, the production of CH(3)*CHOH was independent of O(2)* but dependent upon the concentration of L-arginine. Formation of CH(3)*CHOH was inhibited by substituting D-arginine for L-arginine, or inclusion of the NOS inhibitors N(G)-nitro-L-arginine methyl ester, N(G)-monomethyl-L-arginine and the heme blocker, sodium cyanide. The addition of potassium hydrogen persulfate to NOS I, generating the perferryl complex (NOS-[Fe(5+)=O](3+)) in the absence of oxygen and Ca(2+)/calmodulin, and EtOH resulted in the formation of CH(3)*CHOH. NOS I was found to produce the corresponding alpha-hydroxyalkyl radical from 1-propanol and 2-propanol, but not from 2-methyl-2-propanol. Data demonstrated that the perferryl complex of NOS I in the presence of L-arginine was responsible for catalyses of these secondary reactions.
authors: S
authors: S
authors: Porasuphatana
authors: P
authors: P
authors: Tsai
authors: S
authors: S
authors: Pou
authors: G M
authors: GM
authors: Rosen
mesh_terms: D001120:Arginine / Q000378:metabolism; D002384:Catalysis; D002460:Cell Line; D004578:Electron Spin Resonance Spectroscopy; D000431:Ethanol / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism*; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D015398:Signal Transduction; D019097:Spin Trapping; D013481:Superoxides / Q000378:metabolism; D014162:Transfection; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D005609:Free Radicals; D013481:Superoxides; C066318:perferryl iron; D019323:omega-N-Methylarginine; D000431:Ethanol; D001120:Arginine; D007501:Iron; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I