A chemical model for the H2O2 promoted oxidation by nitric oxide synthase (NOS) has been developed. Biomimetic oxidations were carried out using H2O2 and tetrakis (perfluorophenyl) porphyrinato-iron (III) chloride (FeTPPF20) as a catalyst. Similarly to NOS our model system produces Nδ-cyanoornithine, citrulline and NO from NOHA and did not oxidize arginine itself. Based on these results we propose a peroxide shunt to be involved ...