TMC-86A, B and TMC-96, new proteasome inhibitors from Streptomyces sp. TC 1084 and Saccharothrix sp. TC 1094. I. Taxonomy, fermentation, isolation, and biological activities

TMC-86A, B and TMC-96, new 20S proteasome inhibitors with an epoxy-beta-aminoketone moiety, were isolated from the fermentation broth of Streptomyces sp. TC 1084 and Saccharothrix sp. TC 1094, respectively. TMC-86A, B and TMC-96 inhibited the chymotrypsin-like and peptidylglutamyl-peptide hydrolyzing activities of 20S proteasome with the following IC50 values: TMC-86A, 5.1 microM and 3.7microM; TMC-86B, 1.1 microM and 31 microM; TMC-96, 2.9 microM and 3.5 microM, respectively. TMC-86A, B and TMC-96 exhibited the weak inhibitory activity against the trypsin-like activity of 20S proteasome with IC50 values of 51 microM, 250 microM, and 36 microM, respectively. They did not inhibit m-calpain, cathepsin L, and trypsin at 100 microM, suggesting their high specificity for proteasome. Taxonomy of the producing strains is also described.