title: Oxidation and nitration of ribonuclease and lysozyme by peroxynitrite and myeloperoxidase.
abstract: In spite of the many studies on protein modifications by reactive species, knowledge about the products resulting from the oxidation of protein-aromatic residues, including protein-derived radicals and their stable products, remains limited. Here, we compared the oxidative modifications promoted by peroxynitrite and myeloperoxidase/hydrogen peroxide/nitrite in two model proteins, ribonuclease (6Tyr) and lysozyme (3Tyr/6Trp). The formation of protein-derived radicals and products was higher at pH 5.4 and 7.4 for myeloperoxidase and peroxynitrite, respectively. The main product was 3-nitro-Tyr for both proteins and oxidants. Lysozyme rendered similar yields of nitro-Trp, particularly when oxidized by peroxynitrite. Hydroxylated and dimerized products of Trp and Tyr were also produced, but in lower yields. Localization of the main modified residues indicates that peroxynitrite decomposes to radicals within the proteins behaving less specifically than myeloperoxidase. Nitrogen dioxide is emphasized as an important protein modifier.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Caixa Postal 26077, São Paulo, CEP 05513-970, Brazil.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Vaz
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Prado
authors.forename: Paolo
authors.initials: P
authors.lastname: Di Mascio
authors.forename: Ohara
authors.initials: O
authors.lastname: Augusto
mesh_terms: D000818:Animals; D002417:Cattle; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D004529:Egg White; D005609:Free Radicals / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007249:Inflammation / Q000201:enzymology / Q000503:physiopathology; D009113:Muramidase / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism*; D011402:Pronase; D011506:Proteins / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013154:Spleen / Q000201:enzymology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D005609:Free Radicals; D011506:Proteins; D030421:Peroxynitrous Acid; D014443:Tyrosine; D006861:Hydrogen Peroxide; D009195:Peroxidase; D012260:Ribonucleases; D009113:Muramidase; D011402:Pronase