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Cobalt: B12 Enzymes and Coenzymes

  1. Bernhard Kräutler

Published Online: 16 AUG 2013

DOI: 10.1002/9781119951438.eibc0043.pub2

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Kräutler, B. 2013. Cobalt: B12 Enzymes and Coenzymes. Encyclopedia of Inorganic and Bioinorganic Chemistry. 1–26.

Author Information

  1. University of Innsbruck, Innsbruck, Austria

  1. Update based on the original article by Bernhard Kräutler, Encyclopedia of Inorganic Chemistry © 2005 John Wiley & Sons, Ltd

Publication History

  1. Published Online: 16 AUG 2013


Cobalt has its important biological role as metal center of vitamin B12 and of its cofactor variants. The natural B12 derivatives are remarkably complex cobalt-corrins and belong to the larger class of the tetrapyrrolic natural products. The cofactor forms of vitamin B12, the antipernicious anemia factor, are required for human and animal health. With the exception of the (higher) plants, most forms of life appear to depend on vitamin B12 and its natural derivatives. The corrinoids play a particularly basic role in carbon metabolism in archaea and bacteria, which are the only natural sources of the B12 derivatives. These microorganisms have developed extraordinary means for the biosynthesis of the B12 derivatives and for its regulation, in order to cope with the structural and functional complexity of the cobalt-corrinoids. The other B12-dependent forms of life have evolved intricate strategies for the economic and efficient uptake and transport of the corrinoids. The known cofactor functions of the cobalt-corrinoids are due to their extraordinary organometallic chemistry, coupled with their redox chemistry under physiological conditions: adenosylcorrinoids, methylcorrinoids, and reduced corrinoids are the cofactors in various important and unique organometallic enzymes, whose intricate structural and mechanistic properties have been the focus of extensive research activities. The essential role of the corrinoids in organometallic paths of carbon fixation and further carbon metabolism in anerobic microorganisms has attracted particular attention. Indeed, the main chemical reactivity of the corrinoids and their essential biological roles may reflect their possible contributions to the early stages of life on earth. Vitamin B12 and its derivatives thus hold an important position in the life sciences and are at the center of interdisciplinary interests from medicine, biology, chemistry, and physics.


  • bioorganometallic chemistry;
  • biosynthesis;
  • cobalt;
  • corrin;
  • electron transfer;
  • methylation;
  • methyl transfer;
  • organometallic chemistry;
  • radical reactions;
  • rearrangement reactions;
  • synthesis;
  • vitamin B12