Metallo-inhibition of Mnx, a bacterial manganese multicopper oxidase complex
Metallo-inhibition of Mnx, a bacterial manganese multicopper oxidase complex
复制标题
Mnx（一种细菌锰多铜氧化酶复合物）的金属抑制
DOI：
10.1016/j.jinorgbio.2021.111547
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发表时间：
2021
影响因子：
3.9
通讯作者：
Spiro, Thomas G.
中科院分区：
文献类型：
--
作者：
Soldatova, Alexandra V.;Fu, Wen;Romano, Christine A.;Tao, Lizhi;Casey, William H.;Britt, R. David;Tebo, Bradley M.;Spiro, Thomas G.
锰氧化酶复合物，Mnx，从芽孢杆菌。PL-12含有一个多铜氧化酶（MCO），能氧化溶解的Mn（II）形成不溶性的氧化锰（MnO 2）矿物，动力学和光谱分析表明，PL-12的作用机制是通过一个活化步骤，促进形成一系列处于氧化态II、III和IV的双核Mn配合物，从而形成MnO 2。我们现在证明，酶被抑制的第一行过渡金属的顺序欧文-威廉姆斯系列。Zn（II）强烈（Ki~ 1.5 μM）抑制激活和转换步骤，以及Mn（II）结合速率。组合的Zn（II）和Mn（II）浓度依赖性确定抑制是非竞争性的。这一结果是支持电子顺磁共振（EPR）光谱，揭示了未改变的Mnx结合Mn（II）EPR信号，单核和双核，在Zn（II）的存在下。我们推断，抑制性金属结合在一个网站分开的底物网站，并阻止激活酶所需的构象变化，变构抑制的情况下。在Bacillusspore生理学的背景下讨论了这个抑制位点可能的生物学作用。虽然Cu（II）强烈抑制Mnx，但与Irving-Williams系列雅阁，它在低浓度下增加Mnx活化，表明除了四种典型的MCO-Cu之外，弱结合的Cu可能支持酶活性，可能作为电子转移剂。
The manganese oxidase complex, Mnx, fromBacillussp. PL-12 contains a multicopper oxidase (MCO) and oxidizes dissolved Mn(II) to form insoluble manganese oxide (MnO2) mineral. Previous kinetic and spectroscopic analyses have shown that the enzyme's mechanism proceeds through an activation step that facilitates formation of a series of binuclear Mn complexes in the oxidation states II, III, and IV on the path to MnO2formation. We now demonstrate that the enzyme is inhibited by first-row transition metals in the order of the Irving-Williams series. Zn(II) strongly (Ki~ 1.5 μM) inhibits both activation and turnover steps, as well as the rate of Mn(II) binding. The combined Zn(II) and Mn(II) concentration dependence establishes that the inhibition is non-competitive. This result is supported by electron paramagnetic resonance (EPR) spectroscopy, which reveals unaltered Mnx-bound Mn(II) EPR signals, both mono- and binuclear, in the presence of Zn(II). We infer that inhibitory metals bind at a site separate from the substrate sites and block the conformation change required to activate the enzyme, a case of allosteric inhibition. The likely biological role of this inhibitory site is discussed in the context ofBacillusspore physiology. While Cu(II) inhibits Mnx strongly, in accord with the Irving-Williams series, it increases Mnx activation at low concentrations, suggesting that weakly bound Cu, in addition to the four canonical MCO-Cu, may support enzyme activity, perhaps as an electron transfer agent.