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ArticlesCopyright © 1994 by American Association for the Advancement of Science
Nature's carbonylation catalyst: Raman spectroscopic evidence that carbon monoxide binds to iron, not nickel, in CO dehydrogenase
Department of Chemistry, Princeton University, NJ 08544.
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.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)