Reif, Andreas, Zecca, Luigi, Riederer, Peter, Feelisch, Martin and Schmidt, Harald H.H.W.
Nitroxyl oxidizes NADPH in a superoxide dismutase inhibitable manner
Free Radical Biology and Medicine, 30, (7), . (doi:10.1016/S0891-5849(01)00477-4). (PMID:11275480).
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Nitric oxide synthases (NOS) convert L-arginine and N(omega)-hydroxy-L-arginine to nitric oxide (*NO) and/or nitroxyl (NO(-)) in a NADPH-dependent fashion. Subsequently, *NO/superoxide (O(2-)-derived peroxynitrite (ONOO(-)) consumes one additional mol NADPH. The related stoichiometry of NO(-) and NADPH is unclear. We here describe that NO(-) also oxidizes NADPH in a concentration-dependent manner. In the presence of superoxide dismutase (SOD), which also converts NO(-) to *NO, nitrite accumulation was almost doubled and no oxidation of NADPH was observed. Nitrate yield from NO(-) was low, arguing against intermediate ONOO(-) formation. Thus, biologically formed NO(-) may function as an effective pro-oxidant unless scavenged by SOD and affect the apparent NADPH stoichiometry of the NOS reaction.
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