Abstract: A novel M.sub.r 25,000 chymotrypsin-like protease, termed clipsin, which binds to a-1-AChy in a sodium dodecyl sulfate-resistant manner, preferentially degrades .beta.-APP, and shows high activity for a period of a few days in neonatal rat brain is disclosed. Preparation of clipsin in a form that allows clipsin proteolytic activity to be measured under conditions substantially free of the activity other cellular non-clipsin proteases is also disclosed. Further disclosed is a method of identifying potential therapeutic agents for the treatment of selected neuropathologies such as Down's syndrome and Alzheimer's disease by measuring or inhibition of clipsin.

Abstract: A method to assist in the diagnosis of Alzheimer's disease comprising detecting, in bodily fluids, two APP-related proteins, in soluble form, said proteins have an apparent molecular size of about 130 kDa and about 35 kDa, and each of said proteins shares at least one epitope with the C-terminus of APP corresponding substantially to amino acids 676-695 of APP as shown in FIG. 1.