Cathepsin C, also known as DPP-I. It is expected to be located in lysosome and highly expressed in lung, kidney and placenta (PMID: 9092576). This gene encodes a member of the peptidase C1 family and lysosomal cysteine proteinase that appears to be a central coordinator for activation of many serine proteinases in cells of the immune system. Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed to generate heavy and light chains that form a disulfide-linked dimer. Defects in the encoded protein have been shown to be a cause of Papillon-Lefevre syndrome, an autosomal recessive disorder characterized by palmoplantar keratosis and periodontitis. The calculated molecular weight of Cathepsin C is 51 kDa. The 23-kDa band may be a subunit of the protein monomer, while a 100-kda band is a dimer form (PMID: 26884336, 31557781).