Isomerization of aspartyl residue in amyloid beta fragments: The kinetics by real-time 1H NMR under neutral and basic conditions
Isomerization of aspartyl residue in amyloid beta fragments: The kinetics by real-time 1H NMR under neutral and basic conditions
复制标题
β 淀粉样蛋白片段中天冬氨酰残基的异构化：中性和碱性条件下实时 1H NMR 的动力学
DOI：
10.1007/s10953-020-01018-7
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发表时间：
2020
影响因子：
1.2
通讯作者：
E. Okamura
中科院分区：
文献类型：
--
作者：
K. Aki;E. Okamura
在衰老的人体组织中的各种蛋白质中都发现了天冬氨酰 (Asp) 残基的异构体。 Asp 异构化被认为是通过淀粉样β (Aβ) 肽寡聚化促进淀粉样变性的潜在因素之一。实时分析这种异构化仍然具有挑战性，并且尚未提供有关 Asp 原位异构化的信息。在这项工作中，我们报告了通过使用溶液态 1H NMR 原位对 Aβ 片段肽、Aβ2−9 (A2EFRHD7SG9) 和 Aβ2−16 (A2EFRHD7SGYEVHHQK16) 中天冬氨酸异构化的实时定量。异构化产物和反应物的同步 NMR 检测使我们能够根据异构化动力学实时比较 Asp 转化为 isoAsp 的速度。在Aβ2−9中，isoAsp7增加的速率常数k几乎与Asp7减少平行；在 70 °C 下，Asp7 减少的速率常数估计为 (1.3±±0.1) × 10−3h−1，isoAsp7 增加的速率常数估计为 (1.2±±0.1) × 10−3h−1。然而，在 Aβ2−16 中，isoAsp7 的增加远小于 Asp7 的减少。这是由于组氨酸（His）对天冬氨酸异构化的进程有抑制作用； His 咪唑环与琥珀酰亚胺 (Suc) 中间体的偶联使 Suc 的寿命更长，足以干扰向 isoAsp 的转化。
Isomers of aspartyl (Asp) residues have been found in various proteins in aged human tissues. Isomerization of Asp is considered as one of the potential factors to facilitate amyloidosis via the oligomerization of amyloid beta (Aβ) peptides. It is still challenging to analyze such isomerization in real time, and no information has been provided about Asp isomerization in situ. In this work, we report a real-time quantitation of the isomerization at Asp in Aβ fragment peptides, Aβ2−9 (A2EFRHD7SG9) and Aβ2−16 (A2EFRHD7SGYEVHHQK16) by using solution-state1H NMR in situ. The simultaneous NMR detection of isomerization product and reactant enables us to compare how fast Asp is converted to isoAsp in terms of the kinetics of isomerization in real time. In Aβ2−9, the rate constant,kof the increase of isoAsp7 was almost parallel with the decrease of Asp7; the rate constants were estimated to be (1.3 ± 0.1) × 10−3h−1for Asp7 decrease and (1.2 ± 0.1) × 10−3h−1for the increase of isoAsp7 at 70 °C. In Aβ2−16, however,kof isoAsp7 increase was much less than the Asp7 decrease. This is due to an inhibitory effect of histidine (His) on the progress of Asp isomerization; the coupling of His imidazole ring with a succinimide (Suc) intermediate makes Suc lifetime longer enough to interfere with the conversion to isoAsp.