Belactins A and B, new serine carboxypeptidase inhibitors produced by Actinomycete. I. Taxonomy, production, isolation and biological activities

Amoxetamide A, a new anoikis inducer, produced by combined-culture of Amycolatopsis sp. and Tsukamurella pulmonis

Cancer cells including colorectal cancer cells are resistant to anoikis, an anchorage-independent programmed death, which enables metastasis and subsequent survival in a new tumor microenvironment. In this study, we identified a new anoikis inducer, amoxetamide A (1) with a β-lactone moiety, that was produced by combined-culture of Amycolatopsis sp. 26-4 and mycolic acid-containing bacteria (MACB) Tsukamurella pulmonis TP-B0596. The structure of 1 including the stereochemistry of C8 was determined by MS and NMR spectroscopy and modified Mosher's method, and the absolute configurations of C11 and C12 were suggested as 11R and 12S, respectively, by GIAO NMR calculations. Amoxetamide A (1) exhibited anoikis-inducing activity in human colorectal cancer HT-29 cells in anchorage-independent culture conditions.

Biosynthesis and chemical diversity of β-lactone natural products

Covering: up to 2018 β-Lactones are strained rings that are useful organic synthons and pharmaceutical warheads. Over 30 core scaffolds of β-lactone natural products have been described to date, many with potent bioactivity against bacteria, fungi, or human cancer cell lines. β-Lactone natural products are chemically diverse and have high clinical potential, but production of derivatized drug leads has been largely restricted to chemical synthesis partly due to gaps in biochemical knowledge about β-lactone biosynthesis. Here we review recent discoveries in enzymatic β-lactone ring closure via ATP-dependent synthetases, intramolecular cyclization from seven-membered rings, and thioesterase-mediated cyclization during release from nonribosomal peptide synthetase assembly lines. We also comprehensively cover the diversity and taxonomy of source organisms for β-lactone natural products including their isolation from bacteria, fungi, plants, insects, and marine sponges. This work identifies computational and experimental bottlenecks and highlights future directions for genome-based discovery of biosynthetic gene clusters that may produce novel compounds with β-lactone rings.

The absolute configuration of belactin A, a beta-lactone-containing serine carboxypeptidase inhibitor: importance of the beta-lactone structure for serine carboxypeptidase inhibition

The absolute configuration of belactin A, a beta-lactone-containing serine carboxypeptidase inhibitor was studied by a crystal X-ray diffraction analysis and its absolute structure was determined to be (2R,3S)-2-¿(3S)-3-[(2-amino-5-chlorophenyl)carboxamido]-1,1-dimethyl-2-o xobutyl¿-3-methyl-4-oxooxetane. The importance of the beta-lactone structure for inhibitory activity was found by preparing several derivatives of belactin A.

Piperastatin B: a new selective serine carboxypeptidase inhibitor from Streptomyces lavendofoliae MJ908-WF13

Piperastatin B, a new inhibitor of serine carboxypeptidase was purified from a culture broth of Streptomyces lavendofoliae MJ908-WF13 as a minor component by monitoring its inhibitory activity against carboxypeptidase Y (CP-Y). Its structure was determined to be N-formyl-Val-Thr-Leu-Val-Pip-Leu-Pip (pip: piperazic acid, hexahydropyridadine-3-carboxylic acid). Piperastatin B is a highly specific competitive inhibitor of CP-Y (Ki = 55 nM) with little effect on related enzymes and resembles the major component, piperastatin A, in these respects.