ABSTRACT
Peroxynitrite is an inorganic toxin of biological importance. The chemistry of peroxynitrite has a long history, but that does not imply that the reactivity of this molecule is fully understood. This is because the conjugate acid of peroxynitrite is not stable, and until rapid mixing devices became available it was difficult to study it. Peroxynitrite can isomerize to nitrate or decompose to nitrite and dioxygen. The terms decay, isomerization, and decomposition are defined as follows, in agreement with IUPAC conventions. The disappearance of peroxynitrite by any process will be referred to as decay, following usage in atmospheric chemistry. The process that yields nitrate is named isomerization, and that which results in nitrite and dioxygen is decomposition. Cis-trans isomerization refers strictly to the interconversion of cis-peroxynitrite and trars-peroxynitrite. In addition to peroxynitrous acid and nitryl chloride, myeloperoxidase and horseradish peroxidase in combination with nitrite and hydrogen peroxide are capable of nitrating tyrosine residues.
