Manganese(II) Semiquinonato and Manganese(III) Catecholato Complexes with Tridentate Ligand: Modeling the Substrate-Binding State of Manganese-Dependent Catechol Dioxygenase and Reactivity with Molecular Oxygen

摘要

In nature, some metalloenzymes utilize different metal ions as active centers in very similar coordination environments to catalyze a common reaction. In superoxide dismutase (SOD), iron and manganese ions play the same catalytic role, and their coordination structures are almost identical. In spite of the similarity between the iron- and manganese-dependent enzymes, the native enzymes become inactive when they are substituted with the other metal ion. In contrast, in case of iron-dependent catechol dioxygenases, the enzymatic activity remained when the iron(II) ion in the active site was replaced with a manganese(II) or cobalt ion. Therefore, investigations on the role of metal ions in the enzymatic catalytic process as well as reaction mechanisms are attractive subjects to clarify the metal-ion specificity in each enzyme.