Journal article

Publication year: 2002

Pages: 5712-5721

Journal: European Journal of Biochemistry

Volume number: 269

Issue number: 22

ISSN: 0014-2956

Open access status: Bronze

DOI Link: https://doi.org/10.1046/j.1432-1033.2002.03282.x

Publisher: Wiley: No OnlineOpen

Abstract: 
From the membrane fraction of the Gram-positive bacterium Carboxydothermus hydrogenoformans, an enzyme complex catalyzing the conversion of CO to CO2 and H-2 was purified. The enzyme complex showed maximal CO-oxidizing: H-2-evolving enzyme activity with 5% CO in the head-space (450 U per mg protein). Higher CO concentrations inhibited the hydrogenase present in the enzyme complex. For maximal activity, the enzyme complex had to be activated by either CO or strong reductants. The enzyme complex also catalyzed the CO- or H-2-dependent reduction of methylviologen at 5900 and 180 U per mg protein, respectively. The complex was found to be composed of six hydrophilic and two hydrophobic polypeptides. The amino-terminal sequences of the six hydrophilic subunits were determined allowing the identification of the encoding genes in the preliminary genome sequence of C. hydrogenoformans. From the sequence analysis it was deduced that the enzyme complex is formed by a Ni-containing carbon monoxide dehydrogenase (CooS), an electron transfer protein containing four [4Fe-4S] clusters (CooF) and a membrane bound [ NiFe] hydrogenase composed of four hydrophilic subunits and two membrane integral subunits. The hydrogenase part of the complex shows high sequence similarity to members of a small group of [NiFe] hydrogenases with sequence similarity to energy conserving NADH: quinone oxidoreductases. The data support a model in which the enzyme complex is composed of two catalytic sites, a CO- oxidizing site and a H-2-forming site, which are connected via a different iron sulfur cluster containing electron transfer subunits. The exergonic redox reaction catalyzed by the enzyme complex in vivo has to be coupled to energy conservation, most likely via the generation of a proton motive force.

Harvard Citation style: Soboh, B., Linder, D. and Hedderich, R. (2002) Purification and catalytic properties of a CO-oxidizing:H₂-evolving enzyme complex from Carboxydothermus hydrogenoformans, European Journal of Biochemistry, 269(22), pp. 5712-5721. https://doi.org/10.1046/j.1432-1033.2002.03282.x

APA Citation style: Soboh, B., Linder, D., & Hedderich, R. (2002). Purification and catalytic properties of a CO-oxidizing:H₂-evolving enzyme complex from Carboxydothermus hydrogenoformans. European Journal of Biochemistry. 269(22), 5712-5721. https://doi.org/10.1046/j.1432-1033.2002.03282.x