title: Methionine modification in cytochrome-c peroxidase.
abstract: Hydrogen peroxide oxidizes Met-119, Met-230 and Met-231 to the sulfoxide derivatives with equal initial rates in apocytochrome-c peroxidase at pH 4 in 0.1 M sodium acetate buffer. No detectable oxidation of Met-163 and Met-172 occurs under these conditions. Apoenzyme, in which up to two residues of methionine have been oxidized, binds heme stoichiometrically. Heme-reconstituted modified enzyme has an absorption spectrum with the Soret maximum red-shifted compared to that of the native enzyme, indicating a perturbation of the heme environment in the modified enzyme. Heme-reconstituted modified enzyme can bind cyanide with an affinity nearly identical to that of the native enzyme. The heme-reconstituted enzyme loses its ability to react with hydrogen peroxide to form Compound I. The loss of the ability to form Compound I is correlated with the modification of at least one of the residues in the Met-230/Met-231 pair.
authors.affiliation: Department of Chemistry, Northern Illinois University, DeKalb 60115.
authors.forename: K
authors.initials: K
authors.lastname: Kim
authors.forename: J E
authors.initials: JE
authors.lastname: Erman
mesh_terms: D001059:Apoproteins / Q000378:metabolism; D003486:Cyanides / Q000378:metabolism; D003578:Cytochrome-c Peroxidase / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008715:Methionine / Q000378:metabolism*; D010084:Oxidation-Reduction; D010449:Peptide Mapping; D010544:Peroxidases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology
chemical_list: D001059:Apoproteins; D003486:Cyanides; D005656:Fungal Proteins; D008715:Methionine; D006861:Hydrogen Peroxide; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase