Fluorogenic tri-peptide substrate for measuring the trypsin-like peptidase activity of the 20S proteasome. Substrate for the Kex2 endopeptidase from S. Cervisiae, which has substrate specificity toward the C-terminal side of LR, PR and RR sequences. Can be cleaved by Kallikrein 5 with a P1 site preference for basic residues (R and K). This substrate is useful for inhibitor screening and kinetic analysis.