NiII Complex Formation and Protonation States at the Active Site of a Nickel Superoxide Dismutase-Derived Metallopeptide: Implications for the Mechanism of Superoxide Degradation.
NiII Complex Formation and Protonation States at the Active Site of a Nickel Superoxide Dismutase-Derived Metallopeptide: Implications for the Mechanism of Superoxide Degradation.
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镍超氧化物歧化酶衍生金属肽活性位点的 NiIII 络合物形成和质子化状态：对超氧化物降解机制的影响
DOI：
10.1002/chem.201803042
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Buntkowsky
中科院分区：
文献类型：
--
作者：
Tietze;Daniel;Koley Seth;Banabithi;Brauser;Matthias;Tietze;Alesia A;Buntkowsky
利用镍超氧化物歧化酶（NiSOD）活性中心衍生的具有催化活性的小分子金属肽（Nim 6SOD，m6SOD=ACDLAC）研究了超氧化物的降解机理，特别关注了NiII供体原子的质子化状态、质子源以及N末端质子的作用。因此，使用UV/维斯和NMR光谱在不同pH和温度下研究了Ni II ‐金属肽。这些研究表明NiII配位供体原子的pKa大幅降低，导致完全去质子化的NiII活性位点环境。此外，在6.5至10.5的pH范围内没有观察到可滴定的质子。这排除了最近讨论的金属肽的绝热质子隧穿氢原子转移过程，而在天然酶中没有发现。此外，变温1H NMR测量揭示了类似于酶的金属肽的Ni II活性位点内的扩展氢键网络。 对于去质子化的Ni II活性位点，作为催化活性先决条件的残留N末端质子不能作为质子源。最有可能的是，它以端接方式稳定了NiII配位的底物，从而允许内球电子转移。最后，与酶不同的是，金属肽对超氧化物降解的催化速率常数被确定为强烈的pH依赖性，表明本体水直接参与质子供体，这反过来又强烈表明N-末端组氨酸是酶中相应的质子供体。
A small, catalytically active metallopeptide (Nim6SOD, m6SOD=ACDLAC), which was derived from the nickel superoxide dismutase (NiSOD) active site was employed to study the mechanism of superoxide degradation, especially focusing on the protonation states of the NiIIdonor atoms, the proton source, and the role of the N‐terminal proton(s). Therefore, the NiII‐metallopeptide was studied at various pHs and temperatures using UV/Vis and NMR spectroscopy. These studies indicate a strong reduction of the pKaof the NiII‐ligating donor atoms, resulting in a fully deprotonated NiIIactive‐site environment. Furthermore, no titratable proton could be observed within a pH ranging from 6.5 to 10.5. This rules out a recently discussed adiabatic proton tunneling‐like hydrogen‐atom transfer process for the metallopeptides, not found in the native enzyme. Furthermore, variable‐temperature1H NMR measurements uncovered an extended hydrogen‐bond network within the NiIIactive site of the metallopeptide similar to the enzyme. With respect to the deprotonated NiIIactive site, the residual N‐terminal proton, which is a prerequisite for catalytic activity, cannot act as proton source. Most likely, it stabilizes the NiII‐coordinated substrate in an end‐on fashion, thus allowing for an inner‐sphere electron transfer. Lastly, and unlike the enzyme, the catalytic rate constant of superoxide degradation by the metallopeptides was determined to be strongly pH dependent, suggesting bulk water to be directly involved in proton donation, which in turn strongly suggests the N‐terminal histidine to be the respective proton donor in the enzyme.
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影响因子：
16.6
作者：
Shearer, Jason
通讯作者：
Shearer, Jason
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影响因子：
2.9
作者：
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影响因子：
1
作者：
Tietze;Mollenhauer;Buntkowsky
通讯作者：
Buntkowsky
影响因子：
2.9
作者：
Ryan, Kelly C.;Guce, Abigail I.;Johnson, Olivia E.;Brunold, Thomas C.;Cabelli, Diane E.;Garman, Scott C.;Maroney, Michael J.
通讯作者：
Maroney, Michael J.
揭示镍超氧化物歧化酶中底物的位置：模型研究
影响因子：
--
作者：
D. Tietze;S. Voigt;D. Mollenhauer;M. Tischler;D. Imhof;T. Gutmann;L. González;O. Ohlenschläger;H. Breitzke;M. Görlach;G. Buntkowsky
通讯作者：
G. Buntkowsky