Originally isolated from Actinomycetes strain based on its potent in vivo antitumor activity, Epoxomicin is a potent, cell-permeable, selective and irreversible proteasome inhibitor. More potent inhibitor of the chymotrypsin-like activity of the proteasome than Lactacystin (Cat. No. 1709-100). Blocks also trypsin-like and PGPH activities of the proteasome.