Institut für Biologie, Strukturbiologie/Biochemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.
J Biol Inorg Chem. 2012 Feb;17(2):167-73. doi: 10.1007/s00775-011-0839-y. Epub 2011 Sep 9.
Carbon monoxide dehydrogenases (CODHs) catalyze the reversible oxidation of carbon monoxide by reaction with water to yield carbon dioxide, two protons, and two electrons. Two principal types of CODHs can be distinguished. Ni,Fe-containing CODHs contain a [NiFe(4)S(4)OH(x)] cluster within their active site, to which the direct binding of the substrates water and carbon dioxide has been revealed by protein X-ray crystallography. n-Butyl isocyanide is a slow-turnover substrate of CODHs, whose oxidation at the active site shows several parallels to the oxidation of carbon monoxide. Here, we report the crystal structure of CODH-II from Carboxydothermus hydrogenoformans resulting from the enzymatic oxidation of n-butyl isocyanide to n-butyl isocyanate at its active site cluster. The high resolution of the structure (d(min) = 1.28 Å) revealed n-butyl isocyanate bound to the active site cluster and identified a novel type of Ni-C bond in CODHs. The structure suggests the occurrence of tetrahedral in addition to square-planar nickel complexes in product-bound states of this enzyme. Furthermore, we discovered a molecule of n-butyl isocyanide in a hydrophobic channel leading to the active site, revealing a unique architecture for the substrate channel of CODH-II compared with the bifunctional CODHs.
一氧化碳脱氢酶（CODHs）通过与水反应催化一氧化碳的可逆氧化，生成二氧化碳、两个质子和两个电子。可以区分两种主要类型的 CODHs。含 Ni、Fe 的 CODHs 在其活性位点中含有 [NiFe(4)S(4)OH(x)] 簇，通过蛋白质 X 射线晶体学揭示了底物水和二氧化碳的直接结合。正丁基异氰酸酯是 CODHs 的慢转化底物，其在活性位点的氧化与一氧化碳的氧化有几个相似之处。在这里，我们报告了来自产氢羧菌的 CODH-II 的晶体结构，该结构是在其活性位点簇上通过酶促氧化正丁基异氰酸酯生成正丁基异氰酸酯而产生的。结构的高分辨率（d(min) = 1.28 Å）揭示了正丁基异氰酸酯与活性位点簇结合，并在 CODHs 中鉴定出一种新型的 Ni-C 键。该结构表明，在该酶的产物结合态中存在四面体镍配合物，除了平面四方镍配合物之外。此外，我们在通向活性位点的疏水通道中发现了一个正丁基异氰酸酯分子，这揭示了 CODH-II 的底物通道与双功能 CODHs 相比具有独特的结构。
