Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Department of Chemistry, University of California, Irvine, California 92697, USA.
Nat Chem. 2017 Jul;9(7):623-628. doi: 10.1038/nchem.2781. Epub 2017 May 29.
Strong electron-donation from the axial thiolate ligand of cytochrome P450 has been proposed to increase the reactivity of compound I with respect to C-H bond activation. However, it has proven difficult to test this hypothesis, and a direct link between reactivity and electron donation has yet to be established. To make this connection, we have prepared a selenolate-ligated cytochrome P450 compound I intermediate. This isoelectronic perturbation allows for direct comparisons with the wild-type enzyme. Selenium incorporation was achieved using a cysteine auxotrophic Escherichia coli strain. The intermediate was prepared with meta-chloroperbenzoic acid and characterized by UV-visible, Mössbauer and electron paramagnetic resonance spectroscopies. Measurements revealed increased asymmetry around the ferryl moiety, consistent with increased electron donation from the axial selenolate ligand. In line with this observation, we find that the selenolate-ligated compound I cleaves C-H bonds more rapidly than the wild-type intermediate.
强烈的电子供体从细胞色素 P450 的轴向硫醇配体被提出以增加化合物 I 相对于 C-H 键活化的反应性。然而，已经证明很难测试这一假设，并且反应性和电子供体之间的直接联系尚未建立。为了建立这种联系，我们已经制备了硒代氨酸配体的细胞色素 P450 化合物 I 中间产物。这种等电子的扰动允许与野生型酶进行直接比较。硒的掺入是使用半胱氨酸营养缺陷型大肠杆菌菌株来实现的。该中间产物使用间氯过苯甲酸制备，并通过紫外可见、穆斯堡尔和电子顺磁共振光谱进行了表征。测量结果表明，在过氧铁部分周围的不对称性增加，这与轴向硒代氨酸配体的电子供体增加一致。与这一观察结果一致，我们发现硒代氨酸配体的化合物 I 比野生型中间产物更快地裂解 C-H 键。
