Eponemycin, a new antibiotic active against B16 melanoma. I. Production, isolation, structure and biological activity.

Abstract

Streptomyces hygroscopicus No. P247-7 1 (ATCC53709) produced a novel antibiotic eponemycin which exhibited specific in vivo antitumor effect against B 16 melanoma.Structural studies assigned {AS)-1 ,2-epoxy-2-hydroxymethyl-4-(7V-isooctanoyl-L-serylamino)-6-methylhept-6-ene-3-one to eponemycinwhichis unrelated to the knownantitumor antibiotics.In our continuing search for new microbial metabolites with antitumor activity, Streptomyces hygroscopicus No. P247-71 , isolated from a soil sample from the Philippines, was found to produce a novel antibiotic with specific activity against B16 melanoma. The active principle, eponemycin, was recovered from the fermentation broth with ethyl acetate extraction and purified by chromatography. Structural studies revealed it to be a novel molecule composedof isooctanoic acid, L-serine and an aminoepoxyketone. 9-Methylstreptimidone wasisolated as a co-product from the crude extract.Eponemycin showed potent growth inhibition against various tumor cells, but no inhibitory activity against bacteria and fungi. It induced significant prolongation of survival time of mice transplanted with B16 melanoma, while no antitumor activity was observed against P388 leukemia.In this paper, we describe the production, isolation, physico-chemical characterization, structural elucidation and biological properties of eponemycin.Taxonomy of the Producing Strain Source of Organism Strain P247-71 was isolated from a soil sample collected near the root of a tamarind at Mt. Apo, Davao, Mindanao Island, Philippines. MorphologyBoth substrate and aerial mycelia are formed. They are long, well-branched and not fragmented into short filaments. Chains ofarthrospores are born on the aerial hyphae. The spore chain and spore morphology are as follows: 1) Spiral spore chains with 2 to 8 turns, 2) monopodially branched sporophores, 3) spores, oval or barrel-shaped (0.5 to 0.7 by 0.5 to 1.2/mi), and 4) spore ornamentation, rugose or smooth.Sporangium, motile spore and sclerotium are not observed. Cultural and Physiological CharacteristicsStrain P247-71 grows well in most descriptive media. Gray aerial mycelium with hygroscopic black patches is observed on International Streptomyces Project (ISP) agar media except for ISP No. 6 medium.Eponemycin was originally designated BMY-28647 or BU-3862T.

Nocardia asteroides strain GUH-2 induces proteasome inhibition and apoptotic death of cultured cells

“…Although it cannot be ruled out that the apoptosis-inducing factor is distinct from the proteasome inhibitor, recent studies have shown that natural proteasome inhibitors have similar capacities to induce apoptosis in vitro and in vivo [32,39]. These compounds, small molecules with a peptide structure [21,27,42], which are produced and secreted by actinomycete species closely related to Nocardia [18,20,26], interfere with normal protein turnover in cells and can cause programmed cell death [47]. This proapoptotic activity may be due to extended longevity of caspases or modulation of expression of antiapoptotic Bcl-2, a regulator of the intrinsic apoptotic pathway.…”

Development and Characterization of Proteasome Inhibitors

“…Among these, epoxomicin and eponemycin are members of a growing family of α′,β′-epoxyketone natural products having a linear peptide structure ( Fig. 2) (Koguchi et al, 1999(Koguchi et al, , 2000bSugawara et al, 1990;Tsuchiya et al, 1997). We reported the first total synthesis of epoxomicin , isolated from an unidentified actinomycete strain No.Q996-17, and showed that epoxomicin potently inhibits the 20S proteasome (Meng et al, 1999b) using an affinity reagent-labeled epoxomicin (Meng et al, 1999a;Sin et al, 1998).…”

“…Examples include epoxomicin (Hanada et al, 1992), eponemycin (Sugawara et al, 1990), lactacystin (Fenteany et al, 1995), TMC-95s (Koguchi et al, 2000a), phepropeptins (Sekizawa et al, 2001), and epigallocatechin-3-gallate (ECGC) (Nam et al, 2001). Among these, epoxomicin and eponemycin are members of a growing family of α′,β′-epoxyketone natural products having a linear peptide structure ( Fig.…”

The Synthesis of Two Furan‐Based Analogues of the α′,β′‐Epoxy Ketone Proteasome Inhibitor Eponemycin

“…Eponemycin 1 is a potent peptide based cytotoxic agent, isolated in 1989 by Sugawara et al [1] from Streptomyces hygroscopicus (IC 50 ϭ 4 nM in B16 and 25 nM in L1210). Distinguishing features in this molecule are an unnatural γ,δ-dehydroleucine residue, an N-terminal lipophilic isooctanoic acid component, and a reactive C-terminal αЈ,βЈ-epoxy ketone motif.…”