Hayashi, T

J. Am. Chem. Soc. 2009, 131, 15124-15125, 10.1021/ja907428e

Myoglobin (Mb) and horseradish peroxidase (HRP) were both reconstituted with a meso-unsubstituted iron corrole and their electronic configurations and peroxidase activities were investigated. The appearance of the 540 nm band upon incorporation of the iron corrole into apoMb indicates axial coordination by the proximal histidine imidazole in the Mb heme pocket. Based on 1H NMR measurements using the Evans method, the total magnetic susceptibility of the iron corrole reconstituted Mb was evaluated to be S = 3/2. In contrast, although a band does not appear in the vicinity of 540 nm during reconstitution of the iron corrole into the matrix of HRP, a spectrum similar to that of the iron corrole reconstituted Mb is observed upon the addition of dithionite. This observation suggests that the oxidation state of the corrole iron in the reconstituted HRP can be assigned as +4. The catalytic activities of both proteins toward guaiacol oxidation are quite different; the iron corrole reconstituted HRP decelerates H2O2-dependent oxidation of guaiacol, while the same reaction catalyzed by iron corrole reconstituted Mb has the opposite effect and accelerates the reaction. This finding can be attributed to the difference in the oxidation states of the corrole iron when these proteins are in the resting state.

Pan, Y.

RSC Adv. 2013, 3, 22976, 10.1039/c3ra43784a

Horseradish Peroxidase (HRP) is a commercially available and prevalently used peroxidase with no specific substrate binding domain. However, after being incorporated with different metal cations, new catalytic functions were found in biomimetic oxidation of resveratrol. Based on the results of screening, Ca, Cu, Fe and Mn incorporated enzymes showed distinctive effects, either decomposition or dimerization products were observed.

Hayashi, T

J. Am. Chem. Soc. 2007, 129, 12906-12907, 10.1021/ja074685f

The iron porphycene with two propionates at the peripheral positions of the framework was incorporated into the heme pocket of horseradish peroxidase. In the presence of hydrogen peroxide, the ferric iron porphycene was smoothly converted into the iron(IV)-oxo porphycene π-cation radical species, which was confirmed by the appearance of a band around 800 nm in the UV−vis spectrum. The protein with the iron porphycene showed a 10-fold higher reactivity for the thioanisole oxidation when compared to the native protein. In contrast, the guaiacol oxidation proceeded with similar reaction rates in both proteins. The kinetic analyses indicated that the ferric porphycene in the protein more slowly reacts with hydrogen peroxide than the native heme, whereas the high oxidation states show higher reactivities during oxidations of an organic substrate. The formation of the iron(IV)-oxo species of porphycene and its reactivities in the hemoprotein matrix are demonstrated.