Isolation and synthesis of biologically active carbazole alkaloids

F. Vinyl Sulfones and Other Michael Acceptors 4683 G. Azodicarboxamides 4695 IV. Acylating Agents 4695 A. Aza-peptides 4695 B. Carbamates 4699 C. Peptidyl Acyl Hydroxamates 4700 D. â-Lactams and Related Inhibitors 4704 E. Heterocyclic Inhibitors 4714 1. Isocoumarins 4715 2. Benzoxazinones 4722 3. Saccharins 4725 4. Miscellaneous Heterocyclic Inhibitors 4728 V. Phosphonylation Agents 4728 A. Peptide Phosphonates 4728 B. Phosphonyl Fluorides 4734 VI. Sulfonylating Agents 4735 A. Sulfonyl Fluorides 4735 VII. Miscellaneous Inhibitors 4736 VIII. Summary and Perspectives 4737 IX. Acknowledgments 4740 X. Note Added in Proof 4740 XI. References 4740

Irreversible inhibitors of serine, cysteine, and threonine proteases.

The proteasome regulates cellular processes as diverse as cell cycle progression and NF-kappaB activation. In this study, we show that the potent antitumor natural product epoxomicin specifically targets the proteasome. Utilizing biotinylated-epoxomicin as a molecular probe, we demonstrate that epoxomicin covalently binds to the LMP7, X, MECL1, and Z catalytic subunits of the proteasome. Enzymatic analyses with purified bovine erythrocyte proteasome reveal that epoxomicin potently inhibits primarily the chymotrypsin-like activity. The trypsin-like and peptidyl-glutamyl peptide hydrolyzing catalytic activities also are inhibited at 100- and 1,000-fold slower rates, respectively. In contrast to peptide aldehyde proteasome inhibitors, epoxomicin does not inhibit nonproteasomal proteases such trypsin, chymotrypsin, papain, calpain, and cathepsin B at concentrations of up to 50 microM. In addition, epoxomicin is a more potent inhibitor of the chymotrypsin-like activity than lactacystin and the peptide vinyl sulfone NLVS. Epoxomicin also effectively inhibits NF-kappaB activation in vitro and potently blocks in vivo inflammation in the murine ear edema assay. These results thus define epoxomicin as a novel proteasome inhibitor that likely will prove useful in exploring the role of the proteasome in various in vivo and in vitro systems.

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Epoxomicin, a potent and selective proteasome inhibitor, exhibits in vivo antiinflammatory activity

Occurrence, Biogenesis, and Synthesis of Biologically Active Carbazole Alkaloids

Potent activity of carfilzomib, a novel, irreversible inhibitor of the ubiquitin-proteasome pathway, against preclinical models of multiple myeloma

An actinomycete strain No. Q996-17 produced a novel compound, epoxomicin, which exhibited in vivo antitumor activity against B16 melanoma. Structural studies indicated that it is a new member of the epoxy-β-aminoketone group, and is closely related to eponemycin.

Epoxomicin, a new antitumor agent of microbial origin.

Terpestacin, a new antibiotic which inhibits syncytium formation, was isolated from Arthrinium sp. FA1744 (ATCC 74132). The structure of terpestacin was elucidated as a bicyclic sesterterpene on the basis of spectroscopic data and chemical derivatization.

TERPESTACIN, A NEW SYNCYTIUM FORMATION INHIBITOR FROM Arthrinium sp.

New antifungal antibiotics, pradimicins A, B and C were isolated from the culture broth of actinomycete strains proposed as Actinomadura hibisca. They are orange to red pigments containing a benzo[a]naphthacenequinone chromophore substituted with a D-alanine, an aminosugar and a D-xylose (pradimicins A and C).

Pradimicins A, B and C: new antifungal antibiotics. I. Taxonomy, production, isolation and physico-chemical properties.

Melanostatin, a new antibiotic with melanin synthesis inhibitor activity, was isolated from the fermentation broth of Streptomyces clavifer No. N924-2. Its structure was determined by spectral analysis and degradation experiments. Melanostatin strongly inhibited melanin formation in Streptomyces bikiniensis NRRL B-1049 and B16 melanoma cells.

Melanostatin, a new melanin synthesis inhibitor. Production, isolation, chemical properties, structure and biological activity.

Pradimicin FA-1 was produced via directed biosynthesis with substitution of D-serine for D-alanine in the 15-position of pradimicin A. This substitution was achieved by the addition of D-serine to the culture medium of Actinomadura hibisca P157-2. Likewise, pradimicin FA-2 was co-produced along with pradimicin FA-1 when the pradimicins A and C producing strain, A. hibisca A2493 was grown in D-serine-supplemented medium. The new pradimicin analogs share a common core structure of 5,6-dihydrobenzo[a]naphthacenequinone substituted by D-serine at C-15, but differ in the disaccharide moiety at C-5. Pradimicin FA-1 has an N-methylamino sugar and D-xylose. Pradimicin FA-2 is the des-N-methyl analog of pradimicin FA-1. The in vitro and in vivo antifungal activity of the analogs was comparable to that of pradimicin A.

Haruaki Yamamoto

Papers

Epoxomicin, a new antitumor agent of microbial origin.

TERPESTACIN, A NEW SYNCYTIUM FORMATION INHIBITOR FROM Arthrinium sp.

Pradimicins A, B and C: new antifungal antibiotics. I. Taxonomy, production, isolation and physico-chemical properties.

Melanostatin, a new melanin synthesis inhibitor. Production, isolation, chemical properties, structure and biological activity.

New antifungal antibiotics pradimicins FA-1 and FA-2: D-serine analogs of pradimicins A and C.