Redox, haem and CO in enzymatic catalysis and regulation

Biochem Soc Trans. 2012 Jun 1;40(3):501-7. doi: 10.1042/BST20120083.


The present paper describes general principles of redox catalysis and redox regulation in two diverse systems. The first is microbial metabolism of CO by the Wood-Ljungdahl pathway, which involves the conversion of CO or H2/CO2 into acetyl-CoA, which then serves as a source of ATP and cell carbon. The focus is on two enzymes that make and utilize CO, CODH (carbon monoxide dehydrogenase) and ACS (acetyl-CoA synthase). In this pathway, CODH converts CO2 into CO and ACS generates acetyl-CoA in a reaction involving Ni·CO, methyl-Ni and acetyl-Ni as catalytic intermediates. A 70 Å (1 Å=0.1 nm) channel guides CO, generated at the active site of CODH, to a CO 'cage' near the ACS active site to sequester this reactive species and assure its rapid availability to participate in a kinetically coupled reaction with an unstable Ni(I) state that was recently trapped by photolytic, rapid kinetic and spectroscopic studies. The present paper also describes studies of two haem-regulated systems that involve a principle of metabolic regulation interlinking redox, haem and CO. Recent studies with HO2 (haem oxygenase-2), a K+ ion channel (the BK channel) and a nuclear receptor (Rev-Erb) demonstrate that this mode of regulation involves a thiol-disulfide redox switch that regulates haem binding and that gas signalling molecules (CO and NO) modulate the effect of haem.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Acetate-CoA Ligase / metabolism*
  • Aldehyde Oxidoreductases / metabolism*
  • Animals
  • Biocatalysis*
  • Carbon Monoxide / metabolism*
  • Heme / metabolism*
  • Humans
  • Multienzyme Complexes / metabolism*
  • Oxidation-Reduction


  • Multienzyme Complexes
  • Heme
  • Carbon Monoxide
  • Aldehyde Oxidoreductases
  • carbon monoxide dehydrogenase
  • Acetate-CoA Ligase