Screening method to identify inhibitors of asp2.

A method for screening compounds to identify those compounds which inhibit the degradation Asp 2 mediated a polypeptide substrate, the method comprising: providing a cell free assay a reaction system comprising Asp 2 Purified recombinant, optionally as an Fc fusion, and substrate in a suitable reaction buffer; and determining the extent of substrate degradation in the presence of compound compared with the extent of degradation in the absence of test compound assay, wherein the peptide substrate contains a pair of placed marker groups on both sides of the cleavage site, so that degradation of the substrate directly results in the modulation of a fluorescent signal, one marker group carries the signal generator and the other marker group performs the modulator function and wherein the marker groups are xanthenes selected from rhodamines, rhodols and fluoresceins, whereby the absorption spectrum of the modulator (acceptor) overlaps the emission spectrum of the generator (donor) such that changes are observed in the transfer of energy after degradation of the peptide.