• K. V. Rajagopalan
Part of the Biochemistry of the Elements book series (BOTE, volume 3)


Among the members of the second transition series, molybdenum is the only element definitely known to have specific biological functions. With its ability to exist in oxidation states from -2 to +6 and coordination ranging from 4 to 8, the metal has an extraordinarily complex chemistry. No doubt the biological functions of molybdenum stem from the versatility of its chemistry, which allows it to exist in multiple valence states and to participate in facile ligand exchange. Thus it is known that in most of the molybdoenzymes so far examined, the metal attains valence states of +4, +5, and + 6 during the catalytic cycle and that the molybdenum center is capable of binding exogenous ligands such as substrates and inhibitors. In all cases, the metal is tightly bound to the host enzymes, which invariably are complex proteins containing two or more different prosthetic groups. Molybdenum-dependent enzymes have been identified in all species of living systems and facilitate such processes as conversion of N2 and NO 3 - to ammonia in plants and lower organisms, growth of microorganisms on compounds such as NO 3 - , purines and pyridines as carbon and nitrogen sources, utilization of NO 3 - as electron sink, and conversion of sulfite to sulfate in animals. This repertoire of catalytic activities makes molybdenum an essential element for plants and animals, and conditionally so for microorganisms.


Nitrate Reductase Xanthine Oxidase Formate Dehydrogenase Aldehyde Oxidase Xanthine Dehydrogenase 
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Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • K. V. Rajagopalan
    • 1
  1. 1.Department of BiochemistryDuke University Medical CenterDurhamUSA

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