Direct Electrochemistry of Proteins and Enzymes

Abstract

Publisher Summary This chapter summarizes the achievements on direct electron transfer (DET) between redox enzymes and electrodes, with a special focus on haem and copper-containing redox enzymes. Haem enzymes involve peroxidases, catalases, cytochromes of the P450 group, and a variety of multi-cofactor complex enzymes that contain haem(s), along with other cofactors such as flavin(s), copper, and iron–sulphur cluster(s). There are a variety of electron tunneling pathways within the enzyme molecule between the redox active centre and the protein surface. The chapter presents two groups of redox enzymes: the intrinsic and extrinsic ones. To realize efficient DET between redox enzymes and electrodes, a proper orientation of the redox enzyme onto the electrode, through the site of the electron-tunneling pathways, where the partner protein commonly binds or through the domain of the active site exposed to the protein surface, becomes important. The copper sites in the redox proteins have been divided into three classes based on their spectroscopic features that reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. The chapter describes all copper-containing proteins that are divided into four groups according to the structure of their active sites: (1) type-1 copper proteins, (2) type-2 copper enzymes, (3) type-3 copper proteins, and (4)‘‘blue’’ multi-copper oxidases.