Patent ID: 6913918

Claim:
A purified or isolated polypetide comprising an amino acid sequence at least 95% identical to a fragment of the aspartyl protease amino acid sequence set forth in FIG. 3 (SEQ ID NO: 4), wherein the fragment is a contiguous fragment that includes aspartyl protease active site tripeptides DTG and DSG and exhibits aspartyl protease activity involved in processing amyloid precursor protein (APP) into amyloid beta, wherein substitution differences between the amino acid sequence of the polypeptide and the amino acid sequence of the fragment consist of conservative substitutions selected from the group consisting of: (a) isoleucine, valine, leucine or alanine for aliphatic residues; (b) lysine or arginine for basic residues; (c) glutamic acid or asparagine for amide residues; (d) glutamine or asparagine for amide residues; (e) serine or threonine for hydroxyl residues; and (f) phenylalanine or tyrosine for aromatic residues, and wherein the polypeptide exhibits aspartyl protease activity involved in processing APP into amyloid beta.