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Gewählte Publikation:

Mach, L., Stüwe, K., Hagen, A., Ballaun, C., Glössl, J..
(1992): Proteolytic processing and glycosylation of cathepsin B The role of the primary structure of the latent precursor and of the carbohydrate moiety for cell-type specific molecular forms of the enzyme.
Biochem. J., 282, 577-582

Abstract:
The lysosomal cysteine proteinase cathepsin B is synthesized in cultured human hepatoma HepG2 cells as an inactive 44 kDa precursor and subsequently processed to the mature single-chain enzyme with a molecular mass of 33 kDa. Intralysosomal conversion into the two-chain form results in subunits of 27 kDa, 24 kDa (heavy chain) and 5 kDa (light chain). Enzymic deglycosylation reveals that the 27 kDa polypeptide is the glycosylated variant of the carbohydrate-free 24 kDa heavy-chain form. The intracellular transport to the lysosomes is dependent upon mannose 6-phosphate-containing N-linked oligosaccharides. Receptor-mediated endocytosis of human skin-fibroblast-derived procathepsin B by HepG2 cells resulted in processed molecular forms that are not distinguishable from endogenous cathepsin B, thus favouring rather a cell-type-specific processing than structural differences due to the source of the proenzyme. The conversion step of single-chain cathepsin B into the two-chain enzyme is inhibited in vivo by the irreversible cysteineproteinase inhibitors Z-Phe-Ala-CHN2 and, albeit weaker, Z-Phe-Phe-CHN2. Both substances have no effect on the activation of procathepsin B to the mature enzyme. The carbohydrate moiety of cathepsin B exerts no significant influence on the stability and the enzymic activity of the enzyme.
Autor*innen der BOKU Wien:
Glößl Josef
Mach Lukas



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