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Nitric oxide protects Cu,Zn-superoxide dismutase from hydrogen peroxide-induced inactivation

By Yu Shin Kim and Sanghwa Han


AbstractReaction of Cu,Zn-superoxide dismutase (SOD1) and hydrogen peroxide generates a putative oxidant SOD-Cu2+-OH that can inactivate the enzyme and oxidize 5,5′-dimethyl-1-pyrroline-N-oxide (DMPO) to DMPO-OH. In the presence of nitric oxide (NO), the SOD1/H2O2 system is known to produce peroxynitrite (ONOO−). In contrast to the proposed cytotoxicity of NO conferred by ONOO−, we report here a protective role of NO in the H2O2-induced inactivation of SOD1. In a dose-dependent manner, NO suppressed formation of DMPO-OH and inactivation of the enzyme. Fragmentation of the enzyme was not affected by NO. Bicarbonate retarded formation of ONOO−, suggesting that NO competes with bicarbonate for the oxidant SOD-Cu2+-OH. We propose that NO protects SOD1 from H2O2-induced inactivation by reducing SOD-Cu2+-OH to the active SOD-Cu2+ with concomitant production of NO+ which reacts with H2O2 to give ONOO−

Publisher: Federation of European Biochemical Societies. Published by Elsevier B.V.
Year: 2000
DOI identifier: 10.1016/S0014-5793(00)01874-3
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