Cathepsin S (簡稱CTSS)是一種溶小體中的半胱胺酸蛋白質酵素，其特性為中性pH值之下會有高度活性並且有跟彈性蛋白酵素相似的活性。在正常狀態下，CTSS被發現其主要表現在抗原表現細胞(antigen-presenting cells)如小噬細胞(microphage)、B細胞和樹突狀細胞(Dendritic cell)中。像是其他的Cathepsin 一樣，CTSS屬於細胞內蛋白質，在哺乳動物體內先形成先驅蛋白，在低Ph值之下會切割成為成熟的蛋白質。由於CTSS水解彈性蛋白的能力強，推測與動脈粥狀硬化、血管新生過程相關。並且已有研究報導指出CTSS與阿滋海默症、腫瘤轉移、肌肉萎縮有相關性。
本研究主要是將CTSS的基因接在載體pET23a上，以大腸桿菌的系統表現，經過回覆摺疊、活化等過程得到有活性的蛋白質。使用有效而快速的方式來偵測最後得到成熟蛋白質的活性，並利用96孔盤來篩選有效的抑制劑化合物。現在我們已經測量過956抑制劑化合物，分別來在林俊成教授、汪炳鈞教授與謝興邦教授之實驗室。而目前篩選出最有效的抑制劑CCL-JJC-097 (IC50 = 0.26±0.05 nM)。

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