Decay of the HO2 and O2 Radicals Catalyzed by Superoxide Dismutase. A Pulse Radiolytic Investigation

Joseph Rabani*, Dina Klug, Irwin Fridovich

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The pulse radiolysis technique has been employed in the investigation of the dismutation of superoxide radicals, O2 and HO2, in the presence of superoxide dismutase in aqueous solutions. The decay of superoxide radicals in the presence of the enzyme was found to be first order in both enzyme and superoxide concentrations. An apparent second order reaction rate constant was found to be about 2 × 109 M−1 sec−1, decreasing slightly as the pH is increased from 5 to 9.5. A mechanism which accounts for all our observations is proposed. It includes two steps: (1) formation of a product (EO2 or E) from one enzyme (E) molecule and one O2 radical ion; (2) regeneration of E by a reaction of this product with an additional O2 ion radical. The reaction rate constants k (E+O − 2) = (1.4 ± 0.2) × 109 and k (E − (or EO − 2) + O − 2) = (1.9 ± 0.6) × 109 M−1 sec−1 were measured at pH = 7 in an oxygenated 0.16 M sodium formate solution.

Original languageEnglish
Pages (from-to)1095-1106
Number of pages12
JournalIsrael Journal of Chemistry
Volume10
Issue number6
DOIs
StatePublished - 1972

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