CHAPTER 5 - Concepts and Approaches to the Understanding of Electron Transfer Processes in Enzymes containing Multiple Redox Centers

Abstract

This chapter discusses aspects of the electron transfer process that occur in redox-active proteins by using examples from a variety of redox-active enzymes. In the outer-sphere mode of the electron transfer, no bonds are made or broken during the formation and subsequent dissociation of the bimolecular complexes formed by the reacting species. Because the redox-active centers of many proteins are either partly or completely buried within the protein, it is generally acknowledged that a inner-sphere process is unlikely for proteinprotein electron transfer reactions and that the outer-sphere model is more appropriate. With proteins, there is every reason to anticipate that complex formation with each of the different reactants proceeds with varying specificity. In general, those proteins that contain only a single redox center rarely exhibit catalytic activity. Thus, the cytochromes, the blue copper proteins, and the simple iron-sulfur protein are better recognized for exhibiting simple electron transfer capabilities. By contrast, proteins that contain several redox-active centers are most commonly associated with a characteristic and well-defined catalytic function.