Sub-angstrom-resolution crystallography reveals physical distortions that enhance reactivity of a covalent enzymatic intermediate
Sub-angstrom-resolution crystallography reveals physical distortions that enhance reactivity of a covalent enzymatic intermediate
复制标题
DOI：
10.1038/nchem.1728
复制
发表时间：
2013-09-01
期刊：
影响因子：
21.8
通讯作者：
Tittmann, Kai
中科院分区：
文献类型：
--
作者：
Luedtke, Stefan;Neumann, Piotr;Tittmann, Kai
人们普遍认为，酶通过提供一条通过低能量过渡态进行的途径来促进反应。原则上，如果阻止中间体松弛到它们的最低能量状态，从而降低到随后的过渡态的势垒，则可以实现进一步的速率提高。在这里，我们报道了真正的转酮醇酶共价反应中间体的亚埃分辨晶体结构。这些结构揭示了连接辅因子和底物的共价键的显著平面外扭曲超过20度，以及剪切底物碳-碳键(d>；1.6埃)的特定伸长。为了实现这些扭曲，蛋白质的构象似乎阻止了底物-辅因子中间体的松弛。结果表明，降低了对后续步骤的障碍，这与提高能量的中间体一致，并导致更有效的整体过程。
It is recognized widely that enzymes promote reactions by providing a pathway that proceeds through a transition state of lower energy. In principle, further rate enhancements could be achieved if intermediates are prevented from relaxing to their lowest energy state, and thereby reduce the barrier to the subsequent transition state. Here, we report sub-angstrom-resolution crystal structures of genuine covalent reaction intermediates of transketolase. These structures reveal a pronounced out-of-plane distortion of over 20 degrees for the covalent bond that links cofactor and substrate, and a specific elongation of the scissile substrate carbon-carbon bond (d > 1.6 angstrom). To achieve these distortions, the protein's conformation appears to prevent relaxation of a substrate-cofactor intermediate. The results implicate a reduced barrier to the subsequent step that is consistent with an intermediate of raised energy and leads to a more efficient overall process.