Aspartic proteinases: their activation and structural studies.

Besides extracellular mammalian aspartic proteinases also intracellular proteinase cathepsin D is synthesized in the form of a precursor. The evidence is presented that cathepsin D zymogen (cathepsinogen D, procathepsin D) can be activated by a similar mechanism to that of pepsin, releasing an activation segment - peptide(s). The released peptide(s) show inhibitory activity towards cathepsin D and some other aspartic proteinases. The activation peptides released from bovine pepsinogen do not inhibit cathepsins D and E. The structure of different aspartic proteinases was studied by circular dichroism measurements. The binding of pepstatin causes conformational changes in the near UV CD spectrum.