Epoxysuccinyl peptide-derived affinity labels for cathepsin B

Extracellular cysteine proteases, in particular cathepsin B, have been impl icated in a variety of pathological processes. Selectively targeting labels of this enzyme are important tools to gain more detailed understanding of its specific roles. Starting from our recently developed irreversible epoxy succinyl-based inhibitor (R-Gly-Gly-Leu-(2S,3S)-tEps-Leu-Pro-OH, R = OMe), we have synthesized two affinity labels, R = NH-(CH2)(6)-NH-rhodamine B and R = NH-(CH2)(6)-NH-biotin. Using MCF-7 cells, the labeled inhibitors were shown to be virtually non-cell-permeant, Moreover, affinity blot analysis w ith the biotinylated inhibitor allowed a highly sensitive and selective non radioactive detection of active cathepsin B, (C) 2000 Federation of Europea n Biochemical Societies. Published by Elsevier Science B.V. All rights rese rved.