Mechanism of carbon monoxide oxidation at the active site [Ni-4Fe-5S] cluster of carbon monoxide dehydrogenase from Carboxydothermus hydrogenoformans
type: CreativeWork
description: The carbon monoxide (CO) metabolism relies on CO-dehydrogenase (CODH) that oxidizes CO with H2O to CO2. The crystal structures of the native Ni-Fe CODHIICh from the CO-grown thermophilic hydrogenogenic anaerobic bacterium Carboxydothermus hydrogenoformans reveal the active site as a [Ni-4Fe-5S] cluster C, carrying a bimetallic Ni-(mu2S)-Fe1 subsite with a bridging mu2S. This is the assumed site, where the oxidation of CO occurs. However, cluster C in other catalytically active Ni-Fe CODHs, from Rhodospirillum rubrum, Moorella thermoacetica, and recombinant CODHIICh expressed in Escherichia coli, for example, lack the ¥ì2S bridging Ni and Fe and contain a [Ni-4Fe-4S] form of a cluster C. The CO oxidation mechanism proposed based on crystallographical and biochemical studies involved the apical binding of CO at the nickel ion and the activation of water at the Fe1 ion of the cluster. In order to understand how CO interacts with the active site of native CODHIICh and what function does the bridging mu2S ligand fulfill in the enzyme, this research work focuses (i) on the interaction of cluster C with CO analogue potassium cyanide and analysis of the resulting type of nickel coordination and (ii) on the effect of sodium sulfide on the enzymatic activities of the native CODHIICh. Under catalytic conditions, cyanide acts as a competitive inhibitor of CODHIICh with respect to CO. Under N2 gas phase without electron acceptor (non-catalytic conditions), cyanide inhibits CODHIICh at highly reduced state (low redox-potentials - 500 mV), not at oxidized and slightly reduced (- 320 mV) states. Cyanide is not able to inhibit CODHIICh at reduced conditions (- 500 mV) when CO is present in the atmosphere. Therefore, the interaction of cyanide with reduced active site is expected to mimic the substrate. The binding of cyanide to the nickel ion has been discovered by x-ray absorption spectroscopy and confirmed by x-ray crystallography at the atomic resolution. This structure comprises…
abstract: The carbon monoxide (CO) metabolism relies on CO-dehydrogenase (CODH) that oxidizes CO with H2O to CO2. The crystal structures of the native Ni-Fe CODHIICh from the CO-grown thermophilic hydrogenogenic anaerobic bacterium Carboxydothermus hydrogenoformans reveal the active site as a [Ni-4Fe-5S] cluster C, carrying a bimetallic Ni-(mu2S)-Fe1 subsite with a bridging mu2S. This is the assumed site, where the oxidation of CO occurs. However, cluster C in other catalytically active Ni-Fe CODHs, from Rhodospirillum rubrum, Moorella thermoacetica, and recombinant CODHIICh expressed in Escherichia coli, for example, lack the ¥ì2S bridging Ni and Fe and contain a [Ni-4Fe-4S] form of a cluster C. The CO oxidation mechanism proposed based on crystallographical and biochemical studies involved the apical binding of CO at the nickel ion and the activation of water at the Fe1 ion of the cluster. In order to understand how CO interacts with the active site of native CODHIICh and what function does the bridging mu2S ligand fulfill in the enzyme, this research work focuses (i) on the interaction of cluster C with CO analogue potassium cyanide and analysis of the resulting type of nickel coordination and (ii) on the effect of sodium sulfide on the enzymatic activities of the native CODHIICh. Under catalytic conditions, cyanide acts as a competitive inhibitor of CODHIICh with respect to CO. Under N2 gas phase without electron acceptor (non-catalytic conditions), cyanide inhibits CODHIICh at highly reduced state (low redox-potentials - 500 mV), not at oxidized and slightly reduced (- 320 mV) states. Cyanide is not able to inhibit CODHIICh at reduced conditions (- 500 mV) when CO is present in the atmosphere. Therefore, the interaction of cyanide with reduced active site is expected to mimic the substrate. The binding of cyanide to the nickel ion has been discovered by x-ray absorption spectroscopy and confirmed by x-ray crystallography at the atomic resolution. This structure comprises…
author: Ha, Seung-Wook
date published: 2009-05-04
date modified: 2026-07-27T18:49:16Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth