Cathepsin Z, also called cathepsin X or cathepsin P, is a protein that in humans is encoded by the CTSZ gene. It is a member of the cysteine cathepsin family of cysteine proteases, which has 11 members. As one of the 11 cathepsins, cathepsin Z contains distinctive features from others. Cathepsin Z has been reported involved in cancer malignancy and inflammation. This gene is expressed ubiquitously in cancer cell lines and primary tumors and, like other members of this family, may be involved in tumorigenesis. For instance, cathepsin Z promotes invasion and migration via a noncatalytic mechanism, suggesting multiple modes of cell invasion may be involved in cancer malignancy. Cathepsin Z is also reported to have a protective, but not proteolytic, function in inflammatory gastric disease. It is reported in another study that cathepsin Z may be responsible for dopamine neuron death and thus involved in the pathogenic cascade event. Single-nucleotide polymorphism in CTSZ is found associated with tuberculosis susceptibility, indicating that the pathways involving this protein could yield novel therapies for tuberculosis.