Cathepsin L2 belongs to the Peptidase C1 family. Cathepsin L2 can be autocatalytically convertedto the mature form as a proenzyme in lysosomes at pH=7.0. Cathepsin L2 cannot be expressed in normal mammary gland, colon and peritumoral tissue, but it can be expressed in breast carcinomas and colorectal tissues. These suggeats Cathepsin L2 may play a role in tumor processes. Cathepsin L2 is specifically expressed in the testis, thymus, and corneal epithelium.