ROLE OF PROTEIN AND PORPHYRIN IN THE REACTIVITY OF HORSERADISH-PEROXIDASE TOWARD HYDROGEN DONORS

The electronic ground state of the peroxidase compound I π-cation radical has been changed from 2A2u to 2A1u by substituting deuterohemin for the protohemin of the native enzyme. Although the 2A1u ground state is the same one as that taken by the catalase compound I π-cation radical deuterohemin horseradish peroxidase possesses no catalase activity. It thus appears that the protein and not only the ground state of the compound I π-cation radical determines the reactivities of compounds I of horseradish peroxidase toward hydrogen donors. © 1979.