General Features of Dioxygen Activation in Heme Enzymes

General Features of Dioxygen Activation in Heme Enzymes 

As discussed in the first section of this chapter, the P450 cytochromes, NOS, HOs, and cytochrome oxidases are all heme enzymes which are able to activate molecular oxygen. Related heme enzymes, such as the peroxidases and catalases, work with partially reduced dioxygen species. It has always been intriguing that each of these enzymes uses the same cofactor, heme or Fe-protoporphyrin IX, but performs a distinct physiological function. 

In heme enz)mies that are able to activate molecular dioxygen, the porphyrin and proximal ligand provide the heme iron with five coordination sites. Thus, the side-on coordination of peroxide, which is common for nonheme metal-loenzymes and oxygen activation mechanisms, is not usually observed in heme enzymes and is also rare in model metalloporphyrins - 

A common role of the porphyrin ring in oxygen activation is the donation of an electron during the 

P450 Monoxygenase -Oxidase 0 Heme Oxygenase Peroxygenase Peroxidase/Catalase - 

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