Coordination chemistry studies and peroxidase activity of a new artificial metalloenzyme built by the “Trojan horse” strategy

Abstract

In the general context of green chemistry, a considerable research effort is devoted to the elaboration of new artificial metalloproteins that catalyze, under mild conditions, the oxidation of a wide range of organic compounds, using cheap and environmentally friendly oxidants. A new artificial hemoprotein was obtained by the so-called “Trojan horse” strategy involving the non-covalent insertion of a cationic iron–porphyrin–estradiol cofactor into an anti-estradiol antibody. UV–vis titrations showed the formation of a 1/2 antibody/cofactor complex with a dissociation constant K D = 4.10 −7 M. UV–vis determination of the Fe-imidazole binding constants showed that the protein provided a weak steric hindrance around the iron–porphyrin cofactor. The antibody–estradiol–iron–porphyrin complex displayed a peroxidase activity and catalyzed the oxidation of ABTS by H 2O 2 with about double the efficiency of the iron–porphyrin–estradiol alone. Kinetic studies revealed that this was due to a faster formation of the intermediate high valent iron–oxo species in the presence of the antibody protein. Consequently, the association of an anti-estradiol antibody with an iron–porphyrin–estradiol cofactor leads to a new artificial hemoprotein with an interesting peroxidase activity and the “Trojan horse” strategy appears as a valuable method to generate artificial metalloenzymes that could act as biocatalysts for selective oxidations.