{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Cathepsin K is a cysteine protease, which may be secreted as a pro-enzyme and is activated in a low-pH environment such as lysosomes. Cathepsin K accepts Arg and Lys residues at the P1 active site, acting on Proteolytically Activated Receptors (PARs) in extracellular matrix. Cathepsin K also cleaves collagen and degrades bone matrix, and is involved in the mTOR signaling pathway of cellular autophagy and apoptosis. Cathepsin K has also been shown to induce aggregation in platelets and in the Hedgehog signaling pathway. As a protease active in the extracellular matrix and lysosomes, Cathepsin K has been implicated in cancer progression and invasiveness according to literature."}]}]}