Cathepsin Z (CTSZ)

Cathepsin Z or cathepsin X is a lysosomal cysteine proteinase and member of the peptidase C1 family. It exhibits both carboxy-monopeptidase and carboxy-dipeptidase activities. The encoded protein has also been known as cathepsin X and cathepsin P. This gene is expressed ubiquitously in cancer cell lines and primary tumors and, like other members of this family, may be involved in tumorigenesis. The predicted 303-amino acid protein has the domain structure characteristic of cysteine proteinases, including a signal sequence, a prodomain, and a catalytic domain responsible for proteolytic activity. However, it also contains 3 unique peptide insertions. Cathepsin Z shares protein sequence identity with other human cysteine proteinases of the papain family, including 34% with cathepsin C and 26% with cathepsin B.