Proprotein convertase subtilisin/kexin 9 (PCSK9) is a notable target for the treatment of hypercholesterolemia because it regulates the population of the low‐density lipoprotein receptor (LDLR) on liver cells. The PCSK9 zymogen is a serine protease that spontaneously undergoes a double self‐cleavage step. Available X‐ray structures depict the PCSK9 mature state, but the atomic details of the zymogen state of the enzyme are still unknown. Additionally, why the protease activity of PCSK9 is blocked after the second autoprocessing step remains unclear, as this deviates from other members of the PCSK family. By performing constant‐pH molecular dynamics (MD) simulations, we investigated the protonation state of the catalytic triad of PCSK9 and found that it strongly influences the catalytic properties of the enzyme. Moreover, we determined the final step of the maturation process by classical and steered MD simulations. This study could facilitate the identification of ligands capable of interfering with the PCSK9 maturation process.

中文翻译：

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通过分子模拟探索前蛋白转化酶枯草杆菌蛋白酶/ Kexin 9（PCSK9）自动蛋白水解过程：药物设计提示。

前蛋白转化酶枯草杆菌蛋白酶/ kexin 9（PCSK9）是治疗高胆固醇血症的重要靶标，因为它调节肝细胞上低密度脂蛋白受体（LDLR）的数量。PCSK9酶原是一种丝氨酸蛋白酶，自发经历双重自我切割步骤。可用的X射线结构描述了PCSK9成熟状态，但该酶的酶原状态的原子细节仍然未知。另外，为什么在第二个自动加工步骤后PCSK9的蛋白酶活性被阻断的原因仍然不清楚，因为这与PCSK家族的其他成员不同。通过进行恒定pH分子动力学（MD）模拟，我们研究了PCSK9催化三联体的质子化状态，发现它强烈影响酶的催化性能。此外，我们通过经典和定向MD模拟确定了成熟过程的最后一步。这项研究可以有助于鉴定能够干扰PCSK9成熟过程的配体。