Peroxynitrite: an endogenous oxidizing and nitrating agent

Peroxynitrite, the reaction product between nitric oxide ((NO)-N-.) and sup eroxide, has been presumed to be a mediator of cellular and tissue injury i n various pathological situations. It is formed at the convergence of two i ndependent radical-generating metabolic pathways. Its biological effects ar e due to its reactivity towards a large range of molecules including amino acids such as cysteine, methionine, tyrosine and tryptophan, nucleic bases and antioxidants (e.g. phenolics, selenium- and metal-containing compounds, ascorbate and urate). Peroxynitrite reactions involve oxidation and nitrat ion. The chemical properties depend on the presence of CO2 and metallic com pounds as well as the concentrations of reagents and kinetic laws. This com plex chemistry can be explained by the formation of several structural form s and active intermediates released from peroxynitrite.