title: Microperoxidase 8 catalysed nitrogen oxides formation from oxidation of N-hydroxyguanidines by hydrogen peroxide.
abstract: Nitric oxide (NO) is a potent intra- and intercellular messenger involved in the control of vascular tone, neuronal signalling and host response to infection. In mammals, NO is synthesized by oxidation of l-arginine catalysed by hemeproteins called NO-synthases with intermediate formation of Nomega-hydroxy-l-arginine (NOHA). NOHA and some hydroxyguanidines have been shown to be able to deliver nitrogen oxides including NO in the presence of various oxidative systems. In this study, NOHA and a model compound, N-(4-chlorophenyl)-N'-hydroxyguanidine, were tested for their ability to generate NO in the presence of a haemprotein model, microperoxidase 8 (MP8), and hydrogen peroxide. Nitrite and nitrate production along with selective formation of 4-chlorophenylcyanamide was observed from incubations of N-(4-chlorophenyl)-N'-hydroxyguanidine in the presence of MP8 and hydrogen peroxide. In the case of NOHA, the corresponding cyanamide, Ndelta-cyano-L-ornithine, was too unstable under the conditions used and l-citrulline was the only product identified. A NO-specific conversion of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide to 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and formation of MP8-Fe-NO complexes were observed by EPR spectroscopy and low-temperature UV/visible spectroscopy, respectively. These results clearly demonstrate the formation of nitrogen oxides including NO from the oxidation of exogenous hydroxyguanidines by hydrogen peroxide in the presence of a minienzyme such as MP8. The importance of the bioactivation of endogenous (NOHA) or exogenous N-hydroxyguanidines by peroxidases of physiological interest remains to be established in vivo.
authors.affiliation: Laboratoire de Chimie Bioorganique et Bioinorganique, Institut de Chimie Moléculaire d'Orsay, Université Paris-Sud XI, Orsay, France.
authors.forename: Rémy
authors.initials: R
authors.lastname: Ricoux
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Boucher
authors.forename: Dominique
authors.initials: D
authors.lastname: Mandon
authors.forename: Yves-Michel
authors.initials: YM
authors.lastname: Frapart
authors.forename: Yann
authors.initials: Y
authors.lastname: Henry
authors.forename: Daniel
authors.initials: D
authors.lastname: Mansuy
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Mahy
mesh_terms: D001120:Arginine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001565:Benzoates / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D006146:Guanidines / Q000737:chemistry / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism*; D006898:Hydroxylamines; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D001565:Benzoates; D006146:Guanidines; D006898:Hydroxylamines; D007093:Imidazoles; C471270:N-(4-chlorophenyl)-N'-hydroxyguanidine; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009569:Nitric Oxide; C068309:N(omega)-hydroxyarginine; C029604:hydroxyguanidine; D001120:Arginine; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase