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Yu Shin Kim, Sanghwa Han

Superoxide Reactivates Nitric Oxide-Inhibited Catalase

Catalase binds nitric oxide (NO) to generate ferricatalase-NO, an inhibited form of the enzyme. Superoxide (O2?) is also an inactivator of the enzyme. We found, however, that O2? efficiently converted the inhibited ferricatalase-NO to the active ferricatalase without producing detectable intermediates. The reaction slowed down when O2? was disproportionated to H2O2 and O2 by superoxide dismutase, but H2O2 could displace the heme-bound NO slowly to regenerate ferricatalase. Reactivation was observed even under simultaneous generation of NO and O2? suggesting that ferricatalase-NO reacts with O2? fast enough to compete with the rapid reaction of O2? and NO. Formation of peroxynitrite by the simultaneous generation of NO and O2? was only partially inhibited by ferricatalase, presumably due to slow binding of NO to catalase in comparison with the reaction of NO and O2?.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 381, 12/2000
Pages: 1269 - 1271

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