title: The reaction mechanism of plant peroxidases.
abstract: The catalysis of class III plant peroxidases is described based on the reaction scheme of horseradish peroxidase. The mechanism consists in four distinct steps: (a) binding of peroxide to the heme-Fe(III) to form a very unstable peroxide complex, Compound 0; (b) oxidation of the iron to generate Compound I, a ferryl species with a pi-cation radical in the porphyrin ring; (c) reduction of Compound I by one substrate molecule to produce a substrate radical and another ferryl species, Compound II; (d) reduction of Compound II by a second substrate molecute to release a second substrate radical and regenerate the native enzyme. Under unfavourable conditions some inactive enzyme species can be formed, known as dead-end species. Two calcium ions are normally found in plant peroxidases and appear to be important for the catalytic efficiency.
authors.affiliation: Department of Applied Sciences in Biosystems, University of Cagliari, Cagliari, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Longu
authors.forename: Rosaria
authors.initials: R
authors.lastname: Medda
authors.forename: Alessandra
authors.initials: A
authors.lastname: Padiglia
authors.forename: Jens Z
authors.initials: JZ
authors.lastname: Pedersen
authors.forename: Giovanni
authors.initials: G
authors.lastname: Floris
mesh_terms: D002118:Calcium / Q000737:chemistry; D002384:Catalysis; D006735:Horseradish Peroxidase / Q000737:chemistry; D006861:Hydrogen Peroxide; D007527:Isoenzymes / Q000737:chemistry; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry*; D010944:Plants / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002118:Calcium