Cathepsin B (human, recombinant)

Cathepsin B is a lysosomal cysteine protease and member of the papain family of peptidases that has endo- and exopeptidase activity.^1,2 Cathepsin B is translated as an inactive preproprotein containing a signal peptide, precursor peptide, and catalytic domain.² Following removal of the signal peptide, the precursor peptide is cleaved to release a single-chain polypeptide, which can be further cleaved and the pieces connected via disulfide bonds to form a double-chain form of the protein. Cathepsin B is ubiquitously expressed and localizes primarily to the lysosome where the acidic conditions are optimal for its dipeptidyl carboxypeptidase activity.¹ It is involved in lysosomal protein degradation and maintenance of the intracellular proteome but is also found in the cytoplasm, mitochondria, or nucleus, at the plasma membrane, or secreted into the extracellular matrix and is involved in diverse functions, such as cell death, cell division, and degradation of structural proteins.³ In cancer cells, secreted cathepsin B cleaves and activates extracellular matrix proteins involved in invasion and metastasis.^4,5 The expression or protein levels of cathepsin B are increased in a variety of cancers, including esophageal cancer, hepatocellular carcinoma, and prostate cancer. Cathepsin B has a complex role in Alzheimer’s disease, where it degrades amyloid-β but can also form pyroglutamic acid amyloid-β peptide, which has increased neurotoxicity compared with full-length amyloid-β (1-42).^3,6 It is also involved in the binding of viruses to host cells via cleavage of the glycoproteins from Middle East respiratory syndrome coronavirus (MERS-CoV) and Ebola virus.^7,8 Cayman’s Cathepsin B (human, recombinant) protein can be used for enzyme activity assays. The proprotein consists of 332 amino acids, has a calculated molecular weight of 37.2 kDa, and a predicted N-terminus of Phe74 after signal and precursor peptide cleavage. By SDS-PAGE, under reducing conditions, the apparent molecular mass of the protein is 36 or 43 kDa for the pro- and mature forms, respectively, due to glycosylation.

WARNING This product is not for human or veterinary use.

1. Musil, D., Zucic, D., Turk, D., et al. The refined 2.15 Å X-ray crystal structure of human liver cathepsin B: The structural basis for its specificity. EMBO J. 10(9), 2321-2330 (1991).

2. Mort, J.S., and Buttle, D.J. Cathepsin B. Int. J. Biochem. Cell Biol. 29(5), 715-720 (1997).

3. Wang, J., Zheng, M., Yang, X., et al. The role of cathepsin B in pathophysiologies of non-tumor and tumor tissues: A systematic review. J. Cancer 14(12), 2344-2358 (2023).

4. Liu, F., Zhou, T., Zhang, S., et al. Cathepsin B: The dawn of tumor therapy. Eur. J. Med. Chem. 269, 116329 (2024).

5. Cavallo-Medved, D., and Sloan, B.F. Cell Surface Proteases. Current topics in developmental biology 54, 313-333 (2003).

6. Hook, G., Yu, J., Toneff, T., et al. Brain pyroglutamate amyloid-β is produced by cathepsin B and is reduced by the cysteine protease inhibitor E64d, representing a potential Alzheimer’s disease therapeutic. J. Alzheimers. Dis. 41(1), 129-149 (2014).

7. Du, L., Yang, Y., Zhou, Y., et al. MERS-CoV spike protein: A key target for antivirals. Expert Opin. Ther. Targets 21(2), 131-143 (2017).

8. Miller, E.H., and Chandran, K. Filovirus entry into cells - New insights. Curr. Opin. Virol. 2(2), 206-214 (2012).