Amyloid beta-Protein Precursor/metabolism; Endopeptidases/metabolism; Epitopes/metabolism; Protease Inhibitors/pharmacology; Protein Processing, Post-Translational/drug effects; Recombinant Fusion Proteins/metabolism; Alzheimer Disease/drug therapy; Alzheimer Disease/metabolism; Amino Acid Sequence; Amino Acid Substitution; Amyloid Precursor Protein Secretases; Amyloid beta-Protein Precursor/chemistry; Amyloid beta-Protein Precursor/genetics; Amyloid beta-Protein Precursor/immunology; Antibodies, Monoclonal/immunology; Aspartic Acid Endopeptidases; Blotting, Western; Cell Line; Culture Media, Conditioned/chemistry; Culture Media, Conditioned/metabolism; Dipeptides/pharmacology; Enzyme-Linked Immunosorbent Assay; Epitopes/chemistry; Epitopes/genetics; Epitopes/immunology; Humans; Immunohistochemistry; Isoenzymes/antagonists & inhibitors; Isoenzymes/metabolism; Protease Inhibitors/analysis; Protease Inhibitors/therapeutic use; Recombinant Fusion Proteins/chemistry; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/immunology; Sensitivity and Specificity; Transfection