Reactivity and Redox Potential of Heme-Thiolate Proteins – Results from Enzymes and Enzyme Models

The redox potential is a characteristic parameter of various intermediates of the catalytic cycle of heme-thiolate proteins (cytochromes P450, NO-synthase, chloroperoxidase) which significantly influences catalytic turnover. E0 values of these proteins are surprisingly positive compared to synthetic active site analogues that have an arylthiolate or an alkylthiolate coordinating to the iron. This report examines factors underlying this phenomenon and describes the design of enzyme mimics having redox potentials close to those of heme-thiolate proteins