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Nickel Enzymes & Cofactors

  1. Stephen W. Ragsdale

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0139

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Ragsdale, S. W. 2011. Nickel Enzymes & Cofactors. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. University of Nebraska, Lincoln, NE, USA

Publication History

  1. Published Online: 15 DEC 2011

Abstract

This review covers the structure and function of the eight known Ni enzymes, with a focus on the chemistry and biology of the metallocenter. For the Ni redox enzymes, the Ni ion exhibits versatility in redox properties in exploiting the +3/+2 (superoxide dismutase and hydrogenase), the +2/+1 (hydrogenase, CO dehydrogenase, acetyl-CoA synthase, and methyl-CoM reductase), and perhaps even reaching the 0 (acetyl-CoA synthase) states for the redox enzymes. On the other hand, the nonredox Ni enzymes (urease, glyoxylase-I, aci-reductone dioxygenase) apparently remain in the +2 state during catalysis. The Ni site(s) in these enzymes adopt a wide variety of coordination environments; some form mononuclear square planar or octahedral complexes, while others are homo- or hetero- (with iron) dinuclear with oxo or thiolato bridges and still others join heteromultinuclear clusters. Acetyl-CoA synthase contains the most complex Ni metallocenter yet described, which is a [4Fe–4S]2+ cluster bridged by a cysteine thiolate to a binuclear NiNi center. The three-dimensional structures of all these enzymes are known and some (acetyl-CoA synthase, aci-reductone dioxygenase, CO dehydrogenase, and superoxide dismutase) have been determined in the past two years leading to a significant reinterpretation of spectroscopic results. In many Ni enzymes, density functional theory has begun to play a major role in assigning active-site structures and testing mechanistic hypotheses.

Keywords:

  • methanogenesis;
  • urease;
  • hydrogenase;
  • carbon monoxide dehydrogenase;
  • acetyl-CoA synthase;
  • methyl-coenzyme M reductase;
  • superoxide dismutase;
  • gloxylase I;
  • aci-reductone dioxygenase;
  • acetogenesis;
  • iron–sulfur