Cathepsin D is involved in the clearance of Alzheimer's beta-amyloid protein.

The cerebral deposition of 39-42 residue amyloid beta-protein (Abeta) is a histopathological characteristic of Alzheimer's disease. The present study is aimed at finding proteinases responsible for the intracellular clearance of Abeta. The Abeta-degrading proteinase was purified from rat brain. Amino-terminal sequence analysis indicated the Abeta-degrading proteinase was cathepsin D. Purified cathepsin D hydrolyzed Abeta between Phe19 and Phe20. Cathepsin D is likely to be involved in the intracellular clearance of aggregatable Abeta, since Abeta fragments with Phe20 at the amino-terminus have been reported to be secreted from several lines of cultured cells.