Heme paradigm

Thus, in this heme paradigm, the porphyrin plays an active role in accessing the high-valent oxidation state required for the substrate oxidations. Many of the proposed mechanisms for the nonheme iron oxygen activating enzymes follow this mechanistic model. An important question is how analogous chemical reactions can be carried out in the absence of a porphyrin ligands alternatively, what... 

What distinguishes multicopper oxidases from other copper proteins is that they contain one each of these three types of copper site (Solomon and Lowery, 1993 Solomon et al., 1996). Not only does this make them excellent models for all copper proteins, but because they have four redox-active metal ions, they also serve as paradigms for other enzymes that couple a one-electron reductant to a four-electron oxidant, most notably cytochrome c oxidase. Indeed, the three copper sites (and four copper atoms) in the multicopper oxidases play essentially equivalent roles in comparison to the two heme groups and two copper atoms in cytochrome c oxidase. 

Kurtz DM. 2004. Microbial detoxification of superoxide the non-heme iron reductive paradigm for combating oxidative stress. Acc Chem Res 37(11) 902—908. 

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