From the Laboratory of Pharmaceutical Chemistry and.
Analytical Platform, Faculty of Pharmacy, Université Libre de Bruxelles, 1050 Brussels, Belgium.
J Biol Chem. 2018 Apr 27;293(17):6374-6386. doi: 10.1074/jbc.M117.801076. Epub 2018 Mar 1.
Protein carbamylation by cyanate is a post-translational modification associated with several (patho)physiological conditions, including cardiovascular disorders. However, the biochemical pathways leading to protein carbamylation are incompletely characterized. This work demonstrates that the heme protein myeloperoxidase (MPO), which is secreted at high concentrations at inflammatory sites from stimulated neutrophils and monocytes, is able to catalyze the two-electron oxidation of cyanide to cyanate and promote the carbamylation of taurine, lysine, and low-density lipoproteins. We probed the role of cyanide as both electron donor and low-spin ligand by pre-steady-state and steady-state kinetic analyses and analyzed reaction products by MS. Moreover, we present two further pathways of carbamylation that involve reaction products of MPO, namely oxidation of cyanide by hypochlorous acid and reaction of thiocyanate with chloramines. Finally, using an approach with mice on a high-fat diet and carrying the human MPO gene, we found that during chronic exposure to cyanide, mimicking exposure to pollution and smoking, MPO promotes protein-bound accumulation of carbamyllysine (homocitrulline) in atheroma plaque, demonstrating a link between cyanide exposure and atheroma. In summary, our findings indicate that cyanide is a substrate for MPO and suggest an additional pathway for cyanate formation and protein carbamylation that involves MPO either directly or via its reaction products hypochlorous acid or chloramines. They also suggest that chronic cyanide exposure could promote the accumulation of carbamylated proteins in atherosclerotic plaques.
蛋白质与氰酸盐的氨甲酰化是一种翻译后修饰，与几种（病理）生理状况有关，包括心血管疾病。然而，导致蛋白质氨甲酰化的生化途径尚未完全阐明。本研究表明，髓过氧化物酶（MPO）是一种在炎症部位由受刺激的中性粒细胞和单核细胞分泌的高浓度血红素蛋白，能够催化氰化物的两电子氧化为氰酸盐，并促进牛磺酸、赖氨酸和低密度脂蛋白的氨甲酰化。我们通过预稳态和稳态动力学分析以及 MS 分析反应产物来探测氰化物作为电子供体和低自旋配体的作用。此外，我们提出了另外两种涉及 MPO 反应产物的氨甲酰化途径，即次氯酸氧化氰化物和硫氰酸盐与氯胺的反应。最后，使用高脂肪饮食的携带人 MPO 基因的小鼠 方法，我们发现，在慢性接触氰化物的过程中，模拟接触污染和吸烟，MPO 促进了动脉粥样硬化斑块中蛋白质结合的氨甲酰赖氨酸（同型瓜氨酸）的积累，证明了氰化物暴露与动脉粥样硬化之间的联系。总之，我们的研究结果表明，氰化物是 MPO 的底物，并提出了一种涉及 MPO 直接或通过其反应产物次氯酸或氯胺形成氰酸盐和蛋白质氨甲酰化的额外途径。它们还表明，慢性氰化物暴露可能会促进动脉粥样硬化斑块中氨甲酰化蛋白的积累。
