Model for the Exceptional Reactivity of Peroxiredoxins 2 and 3 with Hydrogen Peroxide A KINETIC AND COMPUTATIONAL STUDY
Model for the Exceptional Reactivity of Peroxiredoxins 2 and 3 with Hydrogen Peroxide A KINETIC AND COMPUTATIONAL STUDY
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DOI：
10.1074/jbc.m111.232355
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发表时间：
2011-05-20
影响因子：
4.8
通讯作者：
Winterbourn, Christine C.
中科院分区：
文献类型：
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作者：
Nagy, Peter;Karton, Amir;Winterbourn, Christine C.
过氧化物氧还蛋白（Peroxiredoxins，Prx）是一种巯基过氧化物酶，对过氧化物具有极高的反应性，但其化学基础尚不清楚。我们提出了强有力的实验证据表明，两个高度保守的精氨酸残基在人类Prx 2和Prx 3的这种活性中起着至关重要的作用。在每种情况下，ArgI或ArgII的点突变（在Prx 3 Arg-123和Arg-146中，分别与活性位点过氧化半胱氨酸（C-p）相距3-4埃或6-7埃）导致反应性损失5个数量级。进一步2个数量级的二阶速率常数的减少，观察到的双精氨酸突变体的两种亚型，这表明这些残基的合作功能。详细的从头算理论计算进行了高水平的G4程序表明强的催化作用的H-键捐赠功能基团的C-p硫和活性和离开氧的过氧化物在一个合作的方式。在计算中使用胍阳离子来模拟精氨酸的官能团，我们能够找到两个过渡结构，这表明与我们实验观察到的速率常数一致的速率增强。我们的研究结果提供了强有力的证据ArgI在激活过氧化物，也涉及氢键ArgII的重要作用。这一机制可以解释过氧化物对过氧化氢的特殊反应性，并可能对蛋白质巯基对过氧化物的反应性有更广泛的影响。
Peroxiredoxins (Prx) are thiol peroxidases that exhibit exceptionally high reactivity toward peroxides, but the chemical basis for this is not well understood. We present strong experimental evidence that two highly conserved arginine residues play a vital role in this activity of human Prx2 and Prx3. Point mutation of either ArgI or ArgII (in Prx3 Arg-123 and Arg-146, which are similar to 3-4 angstrom or similar to 6-7 angstrom away from the active site peroxidative cysteine (C-p), respectively) in each case resulted in a 5 orders of magnitude loss in reactivity. A further 2 orders of magnitude decrease in the second-order rate constant was observed for the double arginine mutants of both isoforms, suggesting a cooperative function for these residues. Detailed ab initio theoretical calculations carried out with the high level G4 procedure suggest strong catalytic effects of H-bond-donating functional groups to the C-p sulfur and the reactive and leaving oxygens of the peroxide in a cooperative manner. Using a guanidinium cation in the calculations to mimic the functional group of arginine, we were able to locate two transition structures that indicate rate enhancements consistent with our experimentally observed rate constants. Our results provide strong evidence for a vital role of ArgI in activating the peroxide that also involves H-bonding to ArgII. This mechanism could explain the exceptional reactivity of peroxiredoxins toward H2O2 and may have wider implications for protein thiol reactivity toward peroxides.