A density functional study of heme-peroxynitrite adducts

The geometries of several possible isomers (N-bonded, O-bonded, protonated, deprotonated) of ferrous and ferric heme-peroxynitrite adducts are examined with density functional theory. Multiple pathways leading to the experimentally observed products of heme-peroxynitrite interactions (ferryl heme, ferric heme, ferrous-dioxygen heme, ferrous-NO heme, nitrate, nitrite, NO2, NO, O2) are identified. These results provide insight into the mechanism of the experimentally demonstrated nitric oxide dioxygenase activity of flavohemoglobin and related hemoproteins.