title: Mechanisms of catalase activity of heme peroxidases.
abstract: In the absence of exogenous electron donors monofunctional heme peroxidases can slowly degrade hydrogen peroxide following a mechanism different from monofunctional catalases. This pseudo-catalase cycle involves several redox intermediates including Compounds I, II and III, hydrogen peroxide reduction and oxidation reactions as well as release of both dioxygen and superoxide. The rate of decay of oxyferrous complex determines the rate-limiting step and the enzymes' resistance to inactivation. Homologous bifunctional catalase-peroxidases (KatGs) are unique in having both a peroxidase and high hydrogen dismutation activity without inhibition reactions. It is demonstrated that KatGs follow a similar reaction pathway as monofunctional peroxidases, but use a unique post-translational distal modification (Met+-Tyr-Trp adduct) in close vicinity to the heme as radical site that enhances turnover of oxyferrous heme and avoids release of superoxide. Similarities and differences between monofunctional peroxidases and bifunctional KatGs are discussed and mechanisms of pseudo-catalase activity are proposed.
authors.affiliation: Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria.
authors.forename: Jutta
authors.initials: J
authors.lastname: Vlasits
authors.forename: Christa
authors.initials: C
authors.lastname: Jakopitsch
authors.forename: Margit
authors.initials: M
authors.lastname: Bernroitner
authors.forename: Marcel
authors.initials: M
authors.lastname: Zamocky
authors.forename: Paul G
authors.initials: PG
authors.lastname: Furtmüller
authors.forename: Christian
authors.initials: C
authors.lastname: Obinger
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002374:Catalase / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D006801:Humans; D010544:Peroxidases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; D010940:Plant Proteins; D006418:Heme; D010544:Peroxidases; D002374:Catalase