Inactivation of astrocytic glutamine synthetase by hydrogen peroxide requires iron
Inactivation of astrocytic glutamine synthetase by hydrogen peroxide requires iron
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DOI：
10.1016/j.neulet.2010.12.019
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发表时间：
2011-02-18
影响因子：
2.5
通讯作者：
Robinson, S. R.
中科院分区：
文献类型：
--
作者：
Fernandes, S. P.;Dringen, R.;Robinson, S. R.
在一些涉及铁介导的氧化应激的神经退行性疾病中，大脑谷氨酰胺合成酶(GS)的比活性降低。本研究调查了过氧化氢是否直接使GS失活，或者GS是否主要由过氧化氢与亚铁反应时Fenton反应产生的羟基自由基失活。将纯化的羊脑GS暴露于超生理浓度的H_2O_2(1 mM，30min)中，其比活力仅降低41%，表明该酶具有较强的抗过氧化氢氧化能力。然而，当与过氧化氢、铁和抗坏血酸共同孵育时，该酶完全失活，这表明在有利于产生羟基自由基的条件下，该酶容易被氧化。同样，在培养的小鼠星形胶质细胞中，特定的GS活性对超生理浓度的H_2O_2具有抵抗力，在1 mM H_2O_2孵育3小时后，大约37%的活性保持不变。这种失活可以被铁络合剂2，2‘-联吡啶或1，10-菲咯啉阻止，但不能被它们的非螯合类似物阻止。这些数据表明，星形细胞GS的失活是由过氧化氢通过Fenton反应间接引起的，因为它需要细胞内可螯合的铁的存在。(C)2010爱思唯尔爱尔兰有限公司。保留所有权利。
The specific activity of brain glutamine synthetase (GS) is lowered in several neurodegenerative diseases that involve iron-mediated oxidative stress. The present study has investigated whether H2O2 directly inactivates GS or whether GS is primarily inactivated by hydroxyl radicals that are produced by the Fenton reaction when H2O2 reacts with ferrous iron. Exposure of purified sheep brain GS to supraphysiological concentrations of H2O2 (1 mM for 30 min) reduced its specific activity by only 41%, indicating that the enzyme is fairly resistant to oxidation by peroxide. However, the enzyme was completely inactivated when co-incubated with H2O2, iron and ascorbate, indicating a vulnerability to oxidation by conditions that favour the production of hydroxyl radicals. Similarly, specific GS activity in cultured mouse astrocytes was resistant to supraphysiological concentrations of H2O2, with approximately 37% of activity remaining 3 h after incubation with 1 mM H2O2. This inactivation was prevented by the iron chelators 2,2'-dipyridyl or 1,10-phenanthroline, but not by their non-chelating analogues. These data suggest that inactivation of astrocytic GS is caused by H2O2 indirectly via the Fenton reaction as it required the presence of chelatable intracellular iron. (C) 2010 Elsevier Ireland Ltd. All rights reserved.