Cathepsin X/Z/P is cysteine cathepsin with unique carboxypeptidase activity. Its expression is associated with cancer and neurodegenerative diseases, although its roles during normal physiology are still poorly understood. Advances in our understanding of its function have been hindered by a lack of available tools that can specifically measure the proteolytic activity of cathepsin X. We present a series of activity-based probes that incorporate a sulfoxonium ylide warhead, which exhibit improved specificity for cathepsin X compared to previously reported probes. We apply these probes to detect cathepsin X activity in cell and tissue lysates, in live cells and in vivo, and to localize active cathepsin X in mouse tissues by microscopy. Finally, we utilize an improved method to generate chloromethylketones, necessary intermediates for synthesis of acyloxymethylketones probes, by way of sulfoxonium ylide intermediates. In conclusion, the probes presented in this study will be valuable for investigating cathepsin X pathophysiology.

中文翻译：

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应用硫鎓叶立德亲电体生成组织蛋白酶 X 选择性活性探针。

组织蛋白酶 X/Z/P 是具有独特羧肽酶活性的半胱氨酸组织蛋白酶。它的表达与癌症和神经退行性疾病有关，尽管它在正常生理学中的作用仍然知之甚少。由于缺乏可以专门测量组织蛋白酶 X 的蛋白水解活性的可用工具，我们对其功能的理解的进展受到了阻碍。我们提出了一系列基于活性的探针，这些探针结合了亚砜叶立德弹头，它们对组织蛋白酶 X 表现出更高的特异性与之前报道的探针相比。我们应用这些探针检测细胞和组织裂解物、活细胞和体内的组织蛋白酶 X 活性，并通过显微镜定位小鼠组织中的活性组织蛋白酶 X。最后，我们利用改进的方法生成氯甲基酮，通过氧化鎓叶立德中间体合成酰氧基甲基酮探针的必要中间体。总之，本研究中提出的探针对于研究组织蛋白酶 X 的病理生理学具有重要意义。