Burst kinetics and redox transformations of the active site manganese ion in oxalate oxidase: Implications for the catalytic mechanism

Mei M. Whittaker, Heng Yen Pan, Erik T. Yukl, James W. Whittaker

    Research output: Contribution to journalArticlepeer-review

    31 Scopus citations

    Abstract

    Oxalate oxidase (EC 1.2.3.4) catalyzes the oxidative cleavage of oxalate to carbon dioxide and hydrogen peroxide. In this study, unusual nonstoichiometric burst kinetics of the steady state reaction were observed and analyzed in detail, revealing that a reversible inactivation process occurs during turnover, associated with a slow isomerization of the substrate complex. We have investigated the underlying molecular mechanism of this kinetic behavior by preparing recombinant barley oxalate oxidase in three distinct oxidation states (Mn(II), Mn(III), and Mn(IV)) and producing a nonglycosylated variant for detailed biochemical and spectroscopic characterization. Surprisingly, the fully reduced Mn(II) form, which represents the majority of the as-isolated native enzyme, lacks oxalate oxidase activity, but the activity is restored by oxidation of the metal center to either Mn(III) or Mn(IV) forms. All three oxidation states appear to interconvert under turnover conditions, and the steady state activity of the enzyme is determined by a balance between activation and inactivation processes. In O2-saturated buffer, a turnover-based redox modification of the enzyme forms a novel superoxidized mononuclear Mn(IV) biological complex. An oxalate activation role for the catalytic metal ion is proposed based on these results.

    Original languageEnglish (US)
    Pages (from-to)7011-7023
    Number of pages13
    JournalJournal of Biological Chemistry
    Volume282
    Issue number10
    DOIs
    StatePublished - Mar 2 2007

    ASJC Scopus subject areas

    • Biochemistry
    • Molecular Biology
    • Cell Biology

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