Cathepsin C (CatC) is a highly conserved tetrameric lysosomal cysteine dipeptidyl aminopeptidase. The best characterized physiological function of CatC is the activation of pro-inflammatory granule-associated serine proteases. These proteases are synthesized as inactive zymogens containing an N-terminal pro-dipeptide, which maintains the zymogen in its inactive conformation and prevents premature activation, which is potentially toxic to the cell. The activation of serine protease zymogens occurs through cleavage of the N-terminal dipeptide by CatC during cell maturation in the bone marrow. In vivo data suggest that pharmacological inhibition of pro-inflammatory serine proteases would suppress or attenuate deleterious effects mediated by these proteases in inflammatory/auto-immune disorders. The pathological deficiency in CatC is associated with Papillon-Lefèvre syndrome (PLS). The patients however do not present marked immunodeficiency despite the absence of active serine proteases in immune defense cells. Hence, the transitory pharmacological blockade of CatC activity in the precursor cells of the bone marrow may represent an attractive therapeutic strategy to regulate activity of serine proteases in inflammatory and immunologic conditions. A variety of CatC inhibitors have been developed both by pharmaceutical companies and academic investigators, some of which are currently being employed and evaluated in preclinical/clinical trials.

组织蛋白酶C（CatC）是高度保守的四聚体溶酶体半胱氨酸二肽基氨基肽酶。CatC的最典型的生理功能是促炎性颗粒相关丝氨酸蛋白酶的激活。这些蛋白酶被合成为含有N末端前肽的无活性酶原，该酶使酶原保持其无活性构象并防止过早活化，这可能对细胞有毒。丝氨酸蛋白酶酶原的激活是通过在骨髓中的细胞成熟过程中，CatC切割N端二肽而发生的。体内数据表明，促炎性丝氨酸蛋白酶的药理学抑制作用将抑制或减弱这些蛋白酶在炎性/自身免疫性疾病中介导的有害作用。CatC的病理缺陷与Papillon-Lefèvre综合征（PLS）相关。然而，尽管免疫防御细胞中不存在活性丝氨酸蛋白酶，但患者并未表现出明显的免疫缺陷。因此，在骨髓的前体细胞中对CatC活性的暂时性药理学阻断可能代表了一种在炎症和免疫学条件下调节丝氨酸蛋白酶活性的有吸引力的治疗策略。制药公司和学术研究人员已经开发出多种CatC抑制剂，其中一些目前正在使用中，并已在临床前/临床试验中进行了评估。