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J. Biol. Chem., Vol. 280, Issue 42, 35372-35381, October 21, 2005

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Characterization of the Oxidase Activity in Mammalian Catalase^*

Anna M. Vetrano, Diane E. Heck, Thomas M. Mariano, Vladimir Mishin, Debra L. Laskin, and Jeffrey D. Laskin1

From the Department of Pharmacology and Toxicology, Rutgers University, Piscataway, New Jersey 08854 and the Department of Environmental and Occupational Medicine, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854

Catalase is a highly conserved heme-containing antioxidant enzyme known for its ability to degrade hydrogen peroxide into water and oxygen. In low concentrations of hydrogen peroxide, the enzyme also exhibits peroxidase activity. We report that mammalian catalase also possesses oxidase activity. This activity, which is detected in purified catalases, cell lysates, and intact cells, requires oxygen and utilizes electron donor substrates in the absence of hydrogen peroxide or any added cofactors. Using purified bovine catalase and 10-acetyl-3,7-dihydroxyphenoxazine as the substrate, the oxidase activity was found to be temperature-dependent and displays a pH optimum of 7–9. The K_m for the substrate is 2.4 x 10^-4 M, and V_max is 4.7 x 10^-5 M/s. Endogenous substrates, including the tryptophan precursor indole, the neurotransmitter precursor -phenylethylamine, and a variety of peroxidase and laccase substrates, as well as carcinogenic benzidines, were found to be oxidized by catalase or to inhibit this activity. Several dietary plant micronutrients that inhibit carcinogenesis, including indole-3-carbinol, indole-3-carboxaldehyde, ferulic acid, vanillic acid, and epigallocatechin-3-gallate, were effective inhibitors of the activity of catalase oxidase. Difference spectroscopy revealed that catalase oxidase/substrate interactions involve the heme-iron; the resulting spectra show time-dependent decreases in the ferric heme of the enzyme with corresponding increases in the formation of an oxyferryl intermediate, potentially reflecting a compound II-like intermediate. These data suggest a mechanism of oxidase activity involving the formation of an oxygen-bound, substrate-facilitated reductive intermediate. Our results describe a novel function for catalase potentially important in metabolism of endogenous substrates and in the action of carcinogens and chemopreventative agents.

Received for publication, April 12, 2005 , and in revised form, August 1, 2005.

^* This work was supported by National Institutes of Health Grants ES06897, CA100994, ES03647, ES004738, GM034310, and ES05022. 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.

¹ To whom correspondence should be addressed: Dept. of Environmental and Occupational Medicine, UMDNJ-Robert Wood Johnson Medical School, 170 Frelinghuysen Rd., Piscataway, NJ 08854. Tel.: 732-445-0176; Fax: 732-445-0119; E-mail: jlaskin{at}eohsi.rutgers.edu.

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