Myeloperoxidase-mediated protein lysine oxidation generates 2-aminoadipic acid and lysine nitrile in vivo.
Myeloperoxidase-mediated protein lysine oxidation generates 2-aminoadipic acid and lysine nitrile in vivo.
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DOI：
10.1016/j.freeradbiomed.2017.01.006
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发表时间：
2017-03
影响因子：
7.4
通讯作者：
Hazen SL
中科院分区：
文献类型：
--
作者：
Lin H;Levison BS;Buffa JA;Huang Y;Fu X;Wang Z;Gogonea V;DiDonato JA;Hazen SL
最近的研究表明，2-氨基己二酸（2-AAA）在有糖尿病风险的受试者中升高，并与葡萄糖稳态有机制联系。先前的研究也表明，在与衰老退行性疾病相关的组织中，蛋白质结合的2-AAA的富集作为赖氨酸残基的氧化翻译后修饰。虽然体外研究表明氧化还原活性过渡金属或髓过氧化物酶（MPO）产生的次氯酸（HOCl）可能产生蛋白结合的2-AAA，但炎症性疾病期间产生2-AAA的机制尚不清楚。在最初的研究中，我们观察到以前用于测量组织2-AAA的传统酸或碱催化蛋白质水解方法可以人工地从另一种潜在的赖氨酸氧化产物赖氨酸腈（LysCN）中生成蛋白质结合的2-AAA。利用经过验证的基于蛋白酶的消化方法结合稳定同位素稀释LC/MS/MS，我们现在报道了蛋白质结合的2-AAA和LysCN都是由次氯酸（HOCl）和白细胞的MPO/H2O2/Cl -系统形成的。在氧化剂与目标蛋白nε -赖氨酸片段摩尔比较低的情况下，2-AAA通过初始的nε -单氯胺中间体生成，通过连续生成瞬态亚胺和半醛中间体最终生成更稳定的2-AAA终产物。当氧化剂与目标蛋白n-赖氨酸胺的比例较高时，蛋白质结合的LysCN通过赖氨酸n-二氯胺中间体的初始生成而形成。在使用MPO敲除小鼠和急性炎症模型的研究中，我们发现MPO在体内炎症过程中形成了游离和蛋白结合的2-AAA，以及产量较低的蛋白结合的LysCN。最后，2-AAA和较小程度的LysCN被证明在人主动脉粥样硬化斑块中富集，已知该组织含有多种mpo催化的蛋白氧化产物。综上所述，这些结果表明mpo介导的蛋白质赖氨酸残基氧化是体内产生2-AAA和LysCN的机制。这些研究进一步支持mpo催化的氧化过程参与动脉粥样硬化和糖尿病风险的发展。
Recent studies reveal 2-aminoadipic acid (2-AAA) is both elevated in subjects at risk for diabetes and mechanistically linked to glucose homeostasis. Prior studies also suggest enrichment of protein-bound 2-AAA as an oxidative post-translational modification of lysyl residues in tissues associated with degenerative diseases of aging. While in vitro studies suggest redox active transition metals or myeloperoxidase (MPO) generated hypochlorous acid (HOCl) may produce protein-bound 2-AAA, the mechanism(s) responsible for generation of 2-AAA during inflammatory diseases are unknown. In initial studies we observed that traditional acid- or base-catalyzed protein hydrolysis methods previously employed to measure tissue 2-AAA can artificially generate protein-bound 2-AAA from an alternative potential lysine oxidative product, lysine nitrile (LysCN). Using a validated protease-based digestion method coupled with stable isotope dilution LC/MS/MS, we now report protein bound 2-AAA and LysCN are both formed by hypochlorous acid (HOCl) and the MPO/H2O2/Cl− system of leukocytes. At low molar ratio of oxidant to target protein Nε-lysine moiety, 2-AAA is formed via an initial Nε-monochloramine intermediate, which ultimately produces the more stable 2-AAA end-product via sequential generation of transient imine and semialdehyde intermediates. At higher oxidant to target protein Nε-lysine amine ratios, protein-bound LysCN is formed via initial generation of a lysine Nε-dichloramine intermediate. In studies employing MPO knockout mice and an acute inflammation model, we show that both free and protein-bound 2-AAA, and in lower yield, protein-bound LysCN, are formed by MPO in vivo during inflammation. Finally, both 2-AAA and to lesser extent LysCN are shown to be enriched in human aortic atherosclerotic plaque, a tissue known to harbor multiple MPO-catalyzed protein oxidation products. Collectively, these results show that MPO-mediated oxidation of protein lysyl residues serves as a mechanism for producing 2-AAA and LysCN in vivo. These studies further support involvement of MPO-catalyzed oxidative processes in both the development of atherosclerosis and diabetes risk.