Inhibition of peroxynitrite-induced nitration of tyrosine by glutathione in the presence of carbon dioxide through both radical repair and peroxynitrate formation.
Peroxynitrite (ONOO-/ONOOH) is assumed to react preferentially with carbon dioxide in vivo to produce nitrogen dioxide (NO2*) and trioxocarbonate(1-) (CO3*-) radicals. We have studied the mechanism by which glutathione (GSH) inhibits the NO2*/CO3*--mediated formation of 3-nitrotyrosine. We found that even low concentrations of GSH strongly inhibit peroxynitrite-dependent tyrosine consumption (IC50 = 660 microM) as well as 3-nitrotyrosine formation (IC50) = 265 microM). From the determination of the level of oxygen produced or consumed under various initial conditions, it is inferred that GSH inhibits peroxynitrite-induced tyrosine consumption by re-reducing (repairing) the intermediate tyrosyl radicals. An additional protective pathway is mediated by the glutathiyl radical (GS*) through reduction of dioxygen to superoxide (O2*-) and reaction with NO2* to form peroxynitrate (O2NOOH/O2NOO-), which is largely unreactive towards tyrosine. Thus, GSH is highly effective in protecting tyrosine against an attack by peroxynitrite in the presence of CO2. Consequently, formation of 3-nitrotyrosine by freely diffusing NO2* radicals is highly unlikely at physiological levels of GSH.
Kirsch
M
M
Institut für Physiologische Chemie, Universitätsklinikum Essen, Germany. michael.kirsch@uni-essen.de
Lehnig
M
M
Korth
H G
HG
Sustmann
R
R
de Groot
H
H
D000975:Antioxidants / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry* / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000737:chemistry*
D000975:Antioxidants; D005609:Free Radicals; D013481:Superoxides; D002245:Carbon Dioxide; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D005978:Glutathione