Epoxomicin was originally isolated from the culture medium of an Actinomycetes strain based on its in vivo antitumor activity against murine B16 melanoma. Epoxomicin is a naturally occurring selective proteasome inhibitor with anti-inflammatory activity. [1] Epoxomicin primarily inhibits the activity of CTRL (chymotrypsin-like proteasome).
The novel α-epoxy ketone moiety of Epoxomicin forms covalent bonds with residues in particular catalytic subunits of the enzyme, disabling activity. The trypsin-like and peptidyl-glutamyl peptide hydrolyzing behaviors of the proteasome were both inhibited by Epoxomicin as well (at 100 and 1,000-fold slower rates, respectively). The ubiquitin-proteasome pathway heavily regulates bone formation, and Epoxomicin was shown to increase both bone volume and bone formation rates in rodents.
Another study demonstrates that exposure to Epoxomicin and other proteasome inhibitors leads to dopaminergic cell death, producing a model of Parkinson's disease in vivo. Epoxomicin is an inhibitor of 20S Proteasome. [2]
References:
1. Meng, L; Mohan, R; Kwok, BH; Elofsson, M; Sin, N; Crews, CM (1999). "Epoxomicin, a potent and selective proteasome inhibitor, exhibits in vivo antiinflammatory activity". PNAS 96 (18): 10403–10408.
2. Epoxomicin, Santa Cruz Biotechnology.
