Ferric exogenous

Umemura, T., Sai, K., Takagi, A., Hasegawa, R. and Kurokawa, Y. (1991). The effects of exogenous glutathione and cysteine on oxidative stress induced by ferric nitrilo-triacetate. Cancer Lett. 58, 49-56. 

Figure 18.20 A plausible ORR catalytic cycle by biomimetic catalysts 2 (Fig. 18.17). Cu is ligated by three imidazoles (omitted for clarity) and potentially an exogenous ligand, whose nature is not known. All intermediates other than ferric-peroxo and ferric-hydroperoxo were prepared independently.

Fig. 14. Redox cycling in the uptake of copper and iron. The lower valent state species is substrate for uptake of copper and iron. The system in the yeast Saccharomyces cerevisiae is diagrammed. The Frel protein reduces environmental Cu " and Fe +. The cuprous ion is substrate for the copper permease, Ctrip. Fe + is substrate for Fet3p its oxidation to Fe + is an obligate step in iron uptake through Ftrlp. Exogenous ferric iron is not taken up by yeast cells unless it is cycled through the ferrireduction-ferrox-idation reactions catalyzed by Frelp and FetSp.

Exogenous antioxidants can preserve the quality of meat products. Radical scavengers appear to be the most effective inhibitors of meat flavor deterioration. However, different substrates and systems respond in different ways. Active ferrous iron may be eliminated physically by chelation with EDTA or phosphates, or chemically by oxidation to its inactive ferric form. 

---