Thesis presented October 29, 2001
Abstract:
Bacterial manganese catalases are involved in the destruction of hydrogen peroxide through its disproportionation in dioxygen and water. Their active site is composed of a pair of manganese ions bridged by a carboxylate residue and two water-derived ligands. During the course of the catalase reaction, the manganese ions shuttle between the bis-MnII and bis-MnIII oxidation states. No reaction intermediate has ever been detected so far. In order to get a better understanding of the mechanistic pathway of these enzymes, we synthesized two series of binuclear manganese complexes. The first one is based on a binucleating phenolate ligand and involves the oxidation states bis-MnII and MnIIMnIII. The second one consists in dioxo bridged manganese complexes of tripod ligands in the oxidation states bis-MnIII and MnIIIMnIV. All complexes have been characterized by X-ray diffraction, EPR, NMR, U.V. visible and infrared spectroscopies, mass spectrometry and magnetic susceptibility. Reactivity with hydrogen peroxide has been studied both from the kinetic and mechanistic viewpoints. These combined experiments have allowed some key points of the mechanism to be evidenced for both series of complexes and, in turn, to propose an original mechanism for the manganese catalases.
Keywords:
Catalase, Biomimetism, Mecanistic study, Kinetic study, Manganese, EPR, Mass spectrometry, Hydrogen peroxide, Isotopic labelling