Microperoxidase 8 catalyzed nitration of phenol by nitrogen dioxide radicals.
Microperoxidase 8 (MP8) is a heme octapeptide obtained by hydrolytic digestion of horse heart cytochrome c. At pH below 9, the heme iron is axially coordinated to the imidazole side chain of His18 and to a water molecule. Replacement of this weak ligand by H2O2 allows the formation of high-valent iron-oxo species which are responsible for both peroxidase-like and cytochrome P450-like activities of MP8. This paper shows that MP8 is able to catalyze the nitration of phenol by nitrite. The reaction requires H2O2 and is inhibited by ligands having a high affinity for the iron, catalase and radical scavengers. This suggests that the nitrating species could be NO2* radicals formed by the oxidation of nitrite by high-valent iron-oxo species. This new activity of MP8 opens a new access to nitro-aromatic compounds under mild conditions and validates the use of this minienzyme to mimick heme peroxidases, especially in the reactions of NO-derived species with biomolecules under oxidative stress conditions.
Ricoux
R
R
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris V, France.
Boucher
J L
JL
Mansuy
D
D
Mahy
J P
JP
D000818:Animals; D002384:Catalysis; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism*; D005609:Free Radicals; D006736:Horses; D006861:Hydrogen Peroxide; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D009206:Myocardium / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009585:Nitrogen Dioxide; D010544:Peroxidases / Q000378:metabolism*; D019800:Phenol / Q000737:chemistry*; D012977:Sodium Nitrite / Q000737:chemistry
D003574:Cytochrome c Group; D005609:Free Radicals; D009566:Nitrates; D019800:Phenol; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase; D012977:Sodium Nitrite; D009585:Nitrogen Dioxide