Electrochemistry of Heme Containing Enzymes - Fundamentals and Applications

Abstract: The thesis is a bioelectrochemical study of heme enzymes, mainly peroxidases and cellobiose dehydrogenases (CDH). It covers both fundamental and applied aspects, viz. studies of the direct electron transfer and kinetics of enzymes on electrodes, and the development of amperometric enzyme-based biosensors. The kinetics of the direct and mediated electron transfer of a wide range of peroxidases (both native and genetically engineered peroxidases) were investigated on graphite and gold electrodes using rotating disk electrode methodology. By genetic engineering of horseradish peroxidase some additional knowledge about the nature of direct ET was obtained. Some new approaches for oriented immobilisation of peroxidase were also investigated. Direct electron transfer of the multi-cofactor enzyme CDH was studied on gold and graphite electrodes with techniques such as voltammetry and spectroelectrochemistry. CDH can be cleaved into its two subunits, one containing the heme cofactor and the other the flavin cofactor, these two subunits were studied individually at the electrode surface to prove that the direct electron transfer proceeds via the heme group. Two biosensors for determination of (di-)phenolic compounds were developed, one using peroxidase and the other using CDH as the biological component.