text: Porphyrin ligands can be innocent (2-) or noninnocent (1-).  In the enzymes chloroperoxidase and cytochrome P450, the porphyrin ligand sustains oxidation during the catalytic cycle, notably in the formation of Compound I.  In other heme proteins, such as myoglobin, ligand-centered redox does not occur and the porphyrin is innocent.