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Acetylene hydratase : a non-redox enzyme with tungsten and iron-sulfur centers at the active site

Acetylene hydratase : a non-redox enzyme with tungsten and iron-sulfur centers at the active site

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KRONECK, Peter M. H., 2016. Acetylene hydratase : a non-redox enzyme with tungsten and iron-sulfur centers at the active site. In: Journal of Biological Inorganic Chemistry : JBIC. 21(1), pp. 29-38. ISSN 0949-8257. eISSN 1432-1327. Available under: doi: 10.1007/s00775-015-1330-y

@article{Kroneck2016-03Acety-33639, title={Acetylene hydratase : a non-redox enzyme with tungsten and iron-sulfur centers at the active site}, year={2016}, doi={10.1007/s00775-015-1330-y}, number={1}, volume={21}, issn={0949-8257}, journal={Journal of Biological Inorganic Chemistry : JBIC}, pages={29--38}, author={Kroneck, Peter M. H.} }

2016-04-20T09:20:48Z Kroneck, Peter M. H. eng 2016-03 Acetylene hydratase : a non-redox enzyme with tungsten and iron-sulfur centers at the active site Kroneck, Peter M. H. In living systems, tungsten is exclusively found in microbial enzymes coordinated by the pyranopterin cofactor, with additional metal coordination provided by oxygen and/or sulfur, and/or selenium atoms in diverse arrangements. Prominent examples are formate dehydrogenase, formylmethanofuran dehydrogenase, and aldehyde oxidoreductase all of which catalyze redox reactions. The bacterial enzyme acetylene hydratase (AH) stands out of its class as it catalyzes the conversion of acetylene to acetaldehyde, clearly a non-redox reaction and a reaction distinct from the reduction of acetylene to ethylene by nitrogenase. AH harbors two pyranopterins bound to W, and a [4Fe-4S] cluster. W is coordinated by four dithiolene sulfur atoms, one cysteine sulfur, and one oxygen ligand. AH activity requires a strong reductant suggesting W(IV) as the active oxidation state. Two different types of reaction pathways have been proposed. The 1.26 Å structure reveals a water molecule coordinated to W which could gain a partially positive net charge by the adjacent protonated Asp-13, enabling a direct attack of C<sub>2</sub>H<sub>2</sub>. To access the W-Asp site, a substrate channel was evolved distant from where it is found in other members of the DMSOR family. Computational studies of this second shell mechanism led to unrealistically high energy barriers, and alternative pathways were proposed where C<sub>2</sub>H<sub>2</sub> binds directly to W. The architecture of the catalytic cavity, the specificity for C<sub>2</sub>H<sub>2</sub> and the results from site-directed mutagenesis do not support this first shell mechanism. More investigations including structural information on the binding of C<sub>2</sub>H<sub>2</sub> are needed to present a conclusive answer. 2016-04-20T09:20:48Z

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