Procathepsin B Fragments
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Introduction
Procathepsin B is a 339 amino acid polypeptide with a molecular weight of approximately 40-45 kD, which is an important substance involved in the production of cathepsin B. Procathepsin B is released to the cytoplasm, and an N-terminal glycosylation site is synthesized in the rough endoplasmic reticulum and glycosylated, and the glycosyl group is further phosphorylated in the Golgi to form mannose-6-phosphoprotein. It is recognized by lysosomal mannose receptors (MPRR) and then sorbent lysosomes and activated by themselves or other proteases. Procathepsin B is proteolytically cleaved into a mature single-stranded active form of 30 kD, which is further cleaved, including removal of the N-terminal propeptide, removal of the 6-amino acid residue at the C-terminus, and internal 127th and 128th amino acid residues. Inter-cutting, the formation of active mature cathepsin B is finally formed.
Mechanism of action
In tumor tissues, the expression of procathepsin B is greatly increased. The cathepsin B secreted by tumor cells lacks the mannose-6-phosphate receptor recognition marker and cannot be taken up by lysosomes, but often in the form of zymogens in the cytosol and extracellular. Procathepsin B has no malignant potential, only mature cathepsin B is involved in tumor invasion and metastasis, but procathepsin B binds to the surface of tumor cells via p11 (the light chain of annexin II heterotetramer), this combination of PB seems to promote tumor invasion and metastasis.
Application of Procathepsin B Fragments
A significant difference (p < 0.05) in serum procathepsin B was noted between cancer and benign tumors, which can be used for differential diagnosis between malignant and benign tumors as a new tumor biomarker. Procathepsin B is highly expressed in tumor tissues and can be used as a marker for tumor organisms for detection, and the expression of procathepsin B differs between benign tumors and malignant tumors and thus can be used to determine tumor type. The binding process of cathepsin B to tumors can affect tumor invasion and metastasis, so it can be used as a target for treating tumors.
References
- Gashenko, E. A., Lebedeva, V. A., Brak, I. V., Tsykalenko, E. A., Vinokurova, G. V., & Korolenko, T. A. (2013). Evaluation of serum procathepsin B, cystatin B and cystatin C as possible biomarkers of ovarian cancer. International journal of circumpolar health, 72(1), 21215.
- Caglic, D., Pungercar, J. R., Pejler, G., Turk, V., & Turk, B. (2007). Glycosaminoglycans facilitate procathepsin B activation through disruption of propeptide-mature enzyme interactions. Journal of Biological Chemistry.
