Substrate Inhibition in Human Indoleamine 2,3-Dioxygenase.
Substrate Inhibition in Human Indoleamine 2,3-Dioxygenase.
复制标题
人吲哚胺 2,3-双加氧酶的底物抑制
DOI：
10.1021/jz500220k
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Nienhaus
中科院分区：
文献类型：
--
作者：
Nickel;Nienhaus;Nienhaus
人吲哚胺2，3-双加氧酶（hIDO）催化L-色氨酸（l-Trp）吡咯环的氧化裂解。在高底物浓度下，催化作用受到抑制;然而，这一观察结果的机制细节仍在争论中。使用时间分辨光谱，我们分析了三元复合物形成hIDO，l-色氨酸，和双原子配体之间的动力学。生理配体双氧（O2）被一氧化碳取代，以排除酶周转。动力学的定量分析表明，三元复合物的形式，每当O2绑定第一，而anl-Trp底物分子到达之前，O2在活性位点引起自抑制。Boundl-Trp阻止配体接近血红素铁，因此，阻碍催化活性三元络合物的形成。
Human indoleamine 2,3-dioxygenase (hIDO) catalyzes the oxidative cleavage of theL-tryptophan (l-Trp) pyrrole ring. Catalysis is inhibited at high substrate concentrations; mechanistic details of this observation are, however, still under debate. Using time-resolved optical spectroscopy, we have analyzed the dynamics of ternary complex formation between hIDO,l-Trp, and a diatomic ligand. The physiological ligand dioxygen (O2) was replaced by carbon monoxide to exclude enzymatic turnover. Quantitative analysis of the kinetics reveals that the ternary complex forms whenever O2binds first, whereas anl-Trp substrate molecule arriving prior to O2in the active site causes self-inhibition. Boundl-Trp prevents the ligand from approaching the heme iron and, therefore, impedes formation of the catalytically active ternary complex.