Nature's carbonylation catalyst: Raman spectroscopic evidence that carbon monoxide binds to iron, not nickel, in CO dehydrogenase.
Carbon monoxide dehydrogenase catalyzes the synthesis of acetyl-coenzyme A from coenzyme A, a methyl group, and carbon monoxide. The carbon monoxide binds to a mixed metal center of the enzyme, which contains nickel bridged to an iron-sulfur cluster. Resonance Raman spectroscopy has been used to identify both C-O stretching and metal-CO stretching vibrations of the carbon monoxide adduct of the enzyme. This adduct was shown by isotopic exchange to be on the pathway for acetyl-coenzyme A synthesis. The metal to which carbon monoxide is bound was established to be iron, not nickel, by preparation of enzyme from bacteria grown on iron-54 and nickel-64. The Fe-CO frequency is low, 360 wave numbers, implying a weak bond, probably because of electron donation from sulfide and thiolate ligands of the iron. A bimetallic mechanism is proposed, in which carbon monoxide binds to an iron atom and is subsequently attacked by a methyl group on a nearby nickel atom, forming an acetyl ligand, which is then transferred to coenzyme A.
Qiu
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Department of Chemistry, Princeton University, NJ 08544.
Kumar
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M
Ragsdale
S W
SW
Spiro
T G
TG
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism*; D002384:Catalysis; D003013:Clostridium / Q000201:enzymology; D003065:Coenzyme A / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007503:Iron Isotopes; D007554:Isotopes; D009097:Multienzyme Complexes; D009532:Nickel / Q000378:metabolism*; D013059:Spectrum Analysis, Raman
D007503:Iron Isotopes; D007554:Isotopes; D009097:Multienzyme Complexes; D000105:Acetyl Coenzyme A; D009532:Nickel; D002248:Carbon Monoxide; D007501:Iron; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase; D003065:Coenzyme A