Cathepsin Z, a Novel Human Cysteine Proteinase with a Short Propeptide Domain and a Unique Chromosomal Location

Abstract

We have identified and characterized a novel human cysteine proteinase of the papain family. A full-length cDNA for this enzyme was cloned from a human brain cDNA library. Nucleotide sequence analysis revealed that the isolated cDNA codes for a polypeptide of 303 amino acids, tentatively called cathepsin Z, that exhibits structural features characteristic of cysteine proteinases. Fluorescent in situ hybridization experiments revealed that the human cathepsin Z gene maps to chromosome 20q13, a location that differs from all cysteine proteinase genes mapped to date. The cDNA encoding cathepsin Z was expressed in Escherichia coli as a fusion protein with glutathione S-transferase, and after purification, the recombinant protein was able to degrade the synthetic peptide benzyloxycarbonyl-PheArg-7-amido-4-methylcoumarin, used as a substrate for cysteine proteinases. Northern blot analysis demonstrated that cathepsin Z is widely expressed in human tissues, suggesting that this enzyme could be involved in the normal intracellular protein degradation taking place in all cell types. Cathepsin Z is also ubiquitously distributed in cancer cell lines and in primary tumors from different sources, suggesting that this enzyme may participate in tumor progression as reported for other cathepsins. Finally, on the basis of a series of distinctive structural features, including diverse peptide insertions and an unusual short propeptide, together with its unique chromosomal location among cysteine proteinases, we propose that cathepsin Z may be the first representative of a novel subfamily of this class of proteolytic enzymes.

The Caenorhabditis elegans Cathepsin Z-like Cysteine Protease, Ce-CPZ-1, Has a Multifunctional Role during the Worms' Development

“…All the nematode cathepsin Z-like sequences, Ce-CPZ-1, Ce-CPZ-2, Ov-CPZ, and Tc-CPZ (Fig. 1B), contain upstream to the cysteine active site the conserved HIP amino acid sequence and an additional two other peptide insertions within the protein sequence characteristic of this new subfamily within the papain family of cysteine proteases (1,5). Although the O. volvulus sequence of the CPZ proteins was the first one cloned (6), it was only subsequently classified as cathepsin Z once a homologous CPZ sequence was cloned from the human brain (Hs-CPZ) (1).…”

“…The human brain cathepsin Z was, however, found to be widely expressed in many tissues, suggesting that this enzyme is possibly involved in the normal intracellular protein degradation that takes place in all cell types. Notably, the enzyme was also found in many cancer cell lines and in primary tumors from different sources, which also suggested a role for this enzyme in tumor progression (1). The human cathepsin Z contains distinctive features that separate it from other human cysteine proteases (2).…”

“…Based on the identification and characterization of a cysteine protease in human brain, a new subfamily of cysteine proteases of the papain family, the cathepsin Z-like enzyme, was recently classified (1). The human brain cathepsin Z was, however, found to be widely expressed in many tissues, suggesting that this enzyme is possibly involved in the normal intracellular protein degradation that takes place in all cell types.…”

“…It functional diversity is generated by the addition of the HIP residues including His 23 in the mature enzyme that provides an anchor for the C terminus of a substrate, thereby allowing favorable enzymesubstrate interaction independent of the P 2 -P 1 sequence. In another study, cathepsin Z-like enzyme (CPZ) 1 was shown to exhibit carboxymonopeptidase as well as carboxydipeptidase activity (4). Moreover, the pro-region of the cathepsin Z is the shortest known to exist in the papain family, and it does not share any significant similarity with the other cathepsin family sequences (1), suggesting that the structural basis for regulating the activity and the processing of this zymogen might be different from that of the other members of the papain family.…”

Synergistic antitumor effects of combined cathepsin B and cathepsin Z deficiencies on breast cancer progression and metastasis in mice

“…This effect can be explained by a compensation of Ctsb deficiency by cathepsin Z (Ctsz) in primary Ctsb-deficient tumor cells derived from breast cancers of Ctsb −/− mice (20). Ctsz (also known as cathepsin X or cathepsin P) belongs to the same Clan CA/C1 protease family as Ctsb (22)(23)(24). Ctsz shows unique features among these proteases, that is, the presence of a RGD motif for integrin binding in its propeptide and strict exopeptidase activity (25,26).…”