title: Crystal structure of the ascorbate peroxidase-ascorbate complex.
abstract: Heme peroxidases catalyze the H2O2-dependent oxidation of a variety of substrates, most of which are organic. Mechanistically, these enzymes are well characterized: they share a common catalytic cycle that involves formation of a two-electron, oxidized Compound I intermediate followed by two single-electron reduction steps by substrate. The substrate specificity is more diverse--most peroxidases oxidize small organic substrates, but there are prominent exceptions--and there is a notable absence of structural information for a representative peroxidase-substrate complex. Thus, the features that control substrate specificity remain undefined. We present the structure of the complex of ascorbate peroxidase-ascorbate. The structure defines the ascorbate-binding interaction for the first time and provides new rationalization of the unusual functional features of the related cytochrome c peroxidase enzyme, which has been a benchmark for peroxidase catalysis for more than 20 years. A new mechanism for electron transfer is proposed that challenges existing views of substrate oxidation in other peroxidases.
authors.affiliation: Department of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, England, UK.
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Sharp
authors.forename: Martin
authors.initials: M
authors.lastname: Mewies
authors.forename: Peter C E
authors.initials: PC
authors.lastname: Moody
authors.forename: Emma Lloyd
authors.initials: EL
authors.lastname: Raven
mesh_terms: D000595:Amino Acid Sequence; D060387:Ascorbate Peroxidases; D001205:Ascorbic Acid / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003578:Cytochrome-c Peroxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000201:enzymology / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D003578:Cytochrome-c Peroxidase; D001205:Ascorbic Acid