Description_x000D_ Application_x000D_ (R)-MG132 has been used in ubiquitination assay and is used as a proteasome inhibitor._x000D_ Biochem/physiol Actions_x000D_ MG132 (carbobenzoxy-Leu-Leu-leucinal) is a tri-peptide aldehyde. It possesses antitumor activity and boosts cytostatic/cytotoxic effects of chemo- and radiotherapy. (R)-MG132 is a potent, membrane-permeable proteasome inhibitor. It can inhibit proteasome activity in lysates of J558L multiple myeloma cells and EMT6 breast cancer cells. The (R)-MG132 stereoisomer is a more effective inhibitor of chymotrypsin-like (ChTL), trypsin-like (TL), and peptidylglutamyl peptide hydrolyzing proteasome (PGPH) activities than the (S)-MG132.