2 Metal Ions at Enzyme Active Sites

Abstract

Publisher Summary This chapter discusses the properties and methods to study metal ions at enzyme active sites. It is estimated that approximately one-third of all enzyme-catalyzed reactions require a metal ion or ions for catalytic activity. The functions of these metal ions can be placed in three broad categories: (1) structural integrity (no specific catalytic function), (2) electron transfer reactions, and (3) electrophilic catalysis. Electrophilic catalysis is the focus of this chapter, in which current data and theories of metalloenzyme catalysis are explored. An aspect of catalysis at metal ion sites on enzymes is the selectivity exhibited by some enzymes for the type of cation (monovalent versus divalent) and/or the oxidation state (+2 versus +3) of the cation. Model studies of metal ion-assisted reactions and of metal-ligand structures is reviewed to establish trends for these types of reactions and features that direct metal ion preference for certain ligand environments.