Mutant cytochrome c peroxidase

With ferryl myoglobin, in contrast to peroxidases, the reactions of the protein free radicals and that of the ferryl haem can be considered as uncoupled from each other. The protein has not been designed to form a cation radical for a specific reaction therefore not only is more than one cation free radical generated, but there is no control over their subsequent reactions. A similar situation can be observed in cytochrome c peroxidase mutants that have lost tryptophan-191. A different amino-acid free radical is still formed that is less stable. Indeed, even in the presence of tryptophan-191, small amounts of other free radicals are formed [237] this is further evidence that even in enzymes it is difficult to exclusively control free radical reactions. 

Figure 13 X-ray crystal structures of oxy forms of cytochrome c peroxidase mutant (W191F CcP) and myoglobin (Mb), used to postulate structures of ferric-hydroperoxy species, a precursor of compound I, as depicted in insets. (Reprinted with permission from Ref. 118. 2001 the American Chemical Society)...

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