Role of Na+ and K+ in enzyme function.
Metal complexation is a key mediator or modifier of enzyme structure and function. In addition to divalent and polyvalent metals, group IA metals Na+ and K+ play important and specific roles that assist function of biological macromolecules. We examine the diversity of monovalent cation (M+)-activated enzymes by first comparing coordination in small molecules followed by a discussion of theoretical and practical aspects. Select examples of enzymes that utilize M+ as a cofactor (type I) or allosteric effector (type II) illustrate the structural basis of activation by Na+ and K+, along with unexpected connections with ion transporters. Kinetic expressions are derived for the analysis of type I and type II activation. In conclusion, we address evolutionary implications of Na+ binding in the trypsin-like proteases of vertebrate blood coagulation. From this analysis, M+ complexation has the potential to be an efficient regulator of enzyme catalysis and stability and offers novel strategies for protein engineering to improve enzyme function.
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Michael J
MJ
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Di Cera
Enrico
E
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology*; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D004798:Enzymes; D012964:Sodium; D011188:Potassium