| Assay Method Information | |
| | In Vitro Enzymatic Cathepsin D (Cat D) FRET (Fluorescence Resonance Energy Transfer) Assay |
| Description: | Recombinant Cat D was expressed in CHO cells. The assay buffer for CatD is 0.05M citrate pH 3.5, 10% DMSO final, 5 mM CHAPS. The CatD enzyme (9 nM) is pre-incubated for one hour with inhibitors, typically in about 1 uL of DMSO according to a serial dilution, is added thereto. The assays are effectively started by the addition of different FRET substrates (20 nM for CatD) and the combination is incubated for one hour. The FRET assay is terminated with by addition of Tris buffer, which raises the pH to neutrality, and the fluorescence is determined. The FRET substrate is a peptide with commercially available fluorophore and quencher, on opposite sides of the BACE cleavage site. The CatD substrate peptide sequence is based on sequence #1 of Table 1 from Gulnik et al. FEBS Letters v413 p 379-384 1997. Proteolytic cleavage of the FRET substrate releases quenching of fluorescence (CatD excitation 500 nm and emission 580 nm).Alternatively, a CatD assay may also be run according to the procedure described in the article, Characterization of new fluorgenic substrates for the rapid and sensitive assay of cathepsin E and cathepsin D, J. Biochem., 125:1137, 1999. In addition, the CatD and cathepsin E assays are described in PCT publication WO2011069934. This WIPO publication describes BACE inhibitor compounds having an amide linker connecting two aromatic groups with extremely poor CatD and/or cathepsin E inhibitory activity (see Table 2).Where available, the in-vitro CatD FRET assay data for each of the Examples, conducted by the first procedure, is provided in Table 1. As shown by the high micromolar CatD data (very poorly active or inactive against CatD), the compounds of the present invention possess the unexpected property of little to no ability to inhibit the activity of CatD. Thus, with this surprising selectivity profile, the compounds of the present invention are believed to minimize, reduce or completely eliminate any risk of retinal atrophy and abnormal development of the eye and of the retinal pigmented epithelium as it relates to the normal function and activity of CatD. |
| Affinity data for this assay | |
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