Cathepsin L (CTSL) has higher activity than cathepsins B and H in the degradation of a variety of physiological protein substrates. It is believed to be responsible for the generation of endostatin from the NC1 domain in collagen XVII. It is responsible for regulating cell cycle, nucleotide-binding domain, leucine-rich–containing family, pyrin domain–containing-3 (NLRP3) inflammasome activation, proteolytic processing of Bid during apoptosis, and TGF-β signaling. It can degrade a wide range of proteins, encompassing enzymes, receptors, and transcription factors. Additionally, it produces active enzymes, receptors, and biologically active peptides through controlled proteolysis. Moreover, Cathepsin L has been observed to enhance tumor cell migration by lowering cell-cell adhesion and breaking down elements of the extracellular matrix. The expression of CTSL escalates in several types of cancers, including glioma, melanoma, pancreatic, prostate, and breast cancer. It plays a major role in the proteolysis of both cellular and endocytosed macromolecules.
