Proposed Mechanism for the Peroxynitrite-Mediated Oxidation of Uric Acid to Allantoin

God, this "Marvin" can be a real ditty to use and can still take a little time, even though I guess it is easier than the other one for this type of thing. This shows two one-electron oxidations of uric acid by ferryl heme (just because I couldn't think of another oxidant I could show the reactions of, easily) and then a series of two-electron oxidations of the products, yielding allantoin. These are proposed mechanisms that I've tried to piece together. The last reaction is shown as a two-electron oxidation, but it wouldn't really be possible in that step. Oxygen would only have 6 electrons after that. Peroxynitrite can, actually, act as either a one- or two-electron oxidant, but not in that case. I didn't feel like showing another one-electron oxidation, assuming that peroxynitrite can even bind to that carbon. The intermediates are, however, known to be intermediates in the oxidation of uric acid by peroxynitrite.