title: pH profile of cytochrome c-catalyzed tyrosine nitration.
abstract: In the present study, we investigated how cytochrome c catalyzed the nitration of tyrosine at various pHs. The cytochrome c-catalyzed nitration of tyrosine occurred in proportion to the concentration of hydrogen peroxide, nitrite or cytochrome c. The cytochromec-catalyzed nitration of tyrosine was inhibited by catalase, sodium azide, cystein, and uric acid. These results show that the cytochrome c-catalyzed nitrotyrosine formation was due to peroxidase activity. The rate constant between cytochrome c and hydrogen peroxide within the pH range of 3-8 was the largest at pH 6 (37 degrees C). The amount of nitrotyrosine formed was the greatest at pH 5. At pH 3, only cytochromec-independent nitration of tyrosine occurred in the presence of nitrite. At this pH, the UV as well as visible spectrum of cytochrome c was changed by nitrite, even in the presence of hydrogen peroxide, probably via the formation of a heme iron-nitric oxide complex. Due to this change, the peroxidase activity of cytochrome c was lost.
authors.affiliation: Department of Environmental and Preventive Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kambayashi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Hitomi
authors.forename: Norio
authors.initials: N
authors.lastname: Kodama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kubo
authors.forename: Junna
authors.initials: J
authors.lastname: Okuda
authors.forename: Kei
authors.initials: K
authors.lastname: Takemoto
authors.forename: Masafumi
authors.initials: M
authors.lastname: Shibamori
authors.forename: Tomoko
authors.initials: T
authors.lastname: Takigawa
authors.forename: Keiki
authors.initials: K
authors.lastname: Ogino
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002384:Catalysis; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism* / Q000494:pharmacology; D016877:Oxidants; D010084:Oxidation-Reduction; D026361:Reactive Nitrogen Species; D012710:Serum Albumin, Bovine; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D009566:Nitrates; D009573:Nitrites; D016877:Oxidants; D026361:Reactive Nitrogen Species; D012710:Serum Albumin, Bovine; C002744:3-nitrotyrosine; D014443:Tyrosine; D045304:Cytochromes c; D006861:Hydrogen Peroxide