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J. Biol. Chem., Vol. 282, Issue 10, 7011-7023, March 9, 2007

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Burst Kinetics and Redox Transformations of the Active Site Manganese Ion in Oxalate Oxidase

IMPLICATIONS FOR THE CATALYTIC MECHANISM^*

From the Department of Environmental and Biomolecular Systems, Oregon Health and Sciences University, Beaverton, Oregon 97006-8921

Oxalate oxidase (EC 1.2.3.4 [EC] ) 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.

Received for publication, October 4, 2006 , and in revised form, January 8, 2007.

^* This work was supported by National Institutes of Health Grant GM42680 (to J. W. W.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1.

¹ To whom correspondence should be addressed: Dept. of Environmental and Biomolecular Systems, Oregon Health and Science University, 20000 N.W. Walker Rd., Beaverton, OR 97006-8921. Tel.: 503-748-1065; Fax: 503-748-1464; E-mail: jim{at}ebs.ogi.edu.

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