Siegbahn Per E M
Department of Physics, Stockholm Centre for Physics, Astronomy and Biotechnology (SCFAB), Stockholm University, S-106 91 Stockholm, Sweden.
Inorg Chem. 2004 Sep 20;43(19):5944-53. doi: 10.1021/ic0498541.
The mechanism of the copper-containing enzyme quercetin 2,3-dioxygenase has been studied using hybrid density functional theory. This enzyme cleaves the O-heterocycle of a flavonol using dioxygen and releases carbon monoxide. Two different pathways for the dioxygen attack on the copper complex have been investigated, and the one where the first attack is on copper is found to be the energetically preferred one. By using this pathway the problem of having to go through a spin-orbit-induced spin crossing is also avoided. The adduct has three unpaired spins and is ideally suited for forming a dioxygen bridging structure, which occurs in the next step. Rather than cleaving the O-O bond in the next step, another C-O bond between dioxygen and the substrate is first formed. Finally, the O-O bond is cleaved, and CO is released in one concerted transition state with a very low barrier. The results are in good agreement with experimental findings. The mechanism is compared to the ones for other similar enzymes studied recently by similar methods.
已使用杂化密度泛函理论研究了含铜酶槲皮素2,3 -双加氧酶的作用机制。该酶利用双氧裂解黄酮醇的O -杂环并释放一氧化碳。研究了双氧进攻铜配合物的两种不同途径，发现首次进攻铜的途径在能量上更有利。通过使用该途径，还避免了必须经历自旋轨道诱导的自旋交叉问题。加合物有三个未成对电子，非常适合形成双氧桥连结构，这发生在下一步。在下一步中，不是裂解O - O键，而是首先在双氧和底物之间形成另一个C - O键。最后，O - O键裂解，CO在一个势垒非常低的协同过渡态中释放。结果与实验发现高度吻合。将该作用机制与最近用类似方法研究的其他类似酶的机制进行了比较。
