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Cation-Activated Enzymes

  1. Jenny P. Glusker

Published Online: 15 MAR 2006

DOI: 10.1002/0470862106.ia039

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Glusker, J. P. 2006. Cation-Activated Enzymes. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. The Fox Chase Cancer Center, Philadelphia, PA, USA

Publication History

  1. Published Online: 15 MAR 2006

Abstract

Cation-activated enzymes are those that require a cation for maximal activity but which still have some activity in the absence of the cation, that is, the activating cation is not an essential part of the enzyme mechanism. The cations involved are generally metal or ammonium ions. The metal ions used are generally Na+, K+, Mg2+, or Ca2+, those that are abundant in nature. In the last 10 years, many crystal structures of cation-activated enzymes have been determined and, in these studies, potassium is the most common activating cation. The geometry of binding and possible conclusions about this activity are the subject of this review. Chosen for description are thrombin (a sodium-activated enzyme), pyruvate kinase, dialkylglycine decarboxylase, diol dehydrase, inosine monophosphate dehydrogenase, and tryptophanase (all potassium-activated enzymes), and alkaline phosphatase (a magnesium-activated enzyme). In some enzymes, the activating cation is near the active site, but in others it is distant. This implies that its function in these two possibilities involves the modification of the charge distribution in the reaction center or else stabilization of the enzyme conformation most suited to the reaction to be catalyzed. These studies provide information on one way in which nature controls enzyme activity, and hopefully further studies will help us learn more possibilities for utilizing these enzyme-control strategies in medicine.

Keywords:

  • cation-activated enzymes;
  • sodium;
  • potassium;
  • magnesium;
  • calcium;
  • thrombin;
  • pyruvate kinase;
  • tryptophanase;
  • alkaline phosphatase;
  • inosine monophosphate dehydrogenase