Discovery of unusual dimeric piperazyl cyclopeptides encoded by a Lentzea flaviverrucosa DSM 44664 biosynthetic supercluster

Rare actinomycetes represent an underexploited source of new bioactive compounds. Here, we report the use of a targeted metabologenomic approach to identify piperazyl compounds in the rare actinomycete Lentzea flaviverrucosa DSM 44664. These efforts to identify molecules that incorporate piperazate building blocks resulted in the discovery and structural elucidation of two dimeric biaryl-cyclohexapeptides, petrichorins A and B. Petrichorin B is a symmetric homodimer similar to the known compound chloptosin, but petrichorin A is unique among known piperazyl cyclopeptides because it is an asymmetric heterodimer. Due to the structural complexity of petrichorin A, solving its structure required a combination of several standard chemical methods plus in silico modeling, strain mutagenesis, and solving the structure of its biosynthetic intermediate petrichorin C for confident assignment. Furthermore, we found that the piperazyl cyclopeptides comprising each half of the petrichorin A heterodimer are made via two distinct nonribosomal peptide synthetase (NRPS) assembly lines, and the responsible NRPS enzymes are encoded within a contiguous biosynthetic supercluster on the L. flaviverrucosa chromosome. Requiring promiscuous cytochrome p450 crosslinking events for asymmetric and symmetric biaryl production, petrichorins A and B exhibited potent in vitro activity against A2780 human ovarian cancer, HT1080 fibrosarcoma, PC3 human prostate cancer, and Jurkat human T lymphocyte cell lines with IC50 values at low nM levels. Cyclic piperazyl peptides and their crosslinked derivatives are interesting drug leads, and our findings highlight the potential for heterodimeric bicyclic peptides such as petrichorin A for inclusion in future pharmaceutical design and discovery programs.Fil: Li, Chunshun. University Of Hawaii; Estados UnidosFil: Hu, Yifei. University Of Hawaii; Estados Unidos. Washington University in St. Louis; Estados UnidosFil: Wu, Xiaohua. University Of Hawaii; Estados UnidosFil: Stumpf, Spencer D.. Washington University in St. Louis; Estados UnidosFil: Qi, Yunci. Washington University in St. Louis; Estados UnidosFil: D'Alessandro, John M.. Washington University in St. Louis; Estados UnidosFil: Nepal, Keshav K.. Washington University in St. Louis; Estados UnidosFil: Sarotti, Ariel Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Cao, Shugeng. University Of Hawaii; Estados UnidosFil: Blodgett, Joshua A.V.. Washington University in St. Louis; Estados Unido

Probing the Role of <i>N</i>‑Acetyl-glutamyl 5‑Phosphate, an Acyl Phosphate, in the Construction of the Azabicycle Moiety of the Azinomycins

The azinomycins are potent antitumor agents produced by the soil bacterium <i>Streptomyces sahachiroi</i> and contain a novel aziridino­[1,2-<i>a</i>]­pyrrolidine core; its synthesis involves at least 14 steps. This study reports the first reconstitution of <i>N</i>-acetylglutamine semialdehyde formation by two enzymes encoded in the azinomycin biosynthetic gene cluster. The reaction proceeds through the formation of an acylphosphate and establishes <i>N</i>-acetyl-glutamyl 5-phosphate and <i>N</i>-acetylglutamine semialdehyde as intermediates in the complex biosynthesis of the aziridino­[1,2-<i>a</i>]­pyrrolidine moiety

Nocardiopsistins A-C: New angucyclines with anti-MRSA activity isolated from a marine sponge-derived Nocardiopsis sp. HB-J378

Marine natural products have become an increasingly important source of new drug leads during recent years. In an attempt to identify novel anti-microbial natural products by bioprospecting deep-sea Actinobacteria, three new angucyclines, nocardiopsistins A-C, were isolated from Nocardiopsis sp. strain HB-J378. Notably, the supplementation of the rare earth salt Lanthanum chloride (LaCl3) during fermentation of HB-J378 significantly increased the yield of these angucyclines. The structures of nocardiopsistins A-C were identified by 1D and 2D NMR and HR-MS data. Nocardiopsistins A-C have activity against MRSA (methicillin-resistant Staphylococcus aureus) with MICs of 3.12–12.5 μg/mL; the potency of nocardiopsistin B is similar to that of the positive control, chloramphenicol. Bioinformatic analysis of the draft genome of HB-J378 identified a set of three core genes in a biosynthetic gene cluster that encode a typical aromatic or type II polyketide synthase (PKS) system, including ketoacyl:ACP synthase α-subunit (KSα), β-subunit (KSβ) and acyl carrier protein (ACP). The production of nocardiopsistins A-C was abolished when the three genes were knocked out, indicating their indispensable role in the production of nocardiopsistins. Keywords: Nocardiopsis, Nocardiopsistins, Angucycline, Anti-MRSA, Actinobacteria, LaCl

Priming of Azabicycle Biosynthesis in the Azinomycin Class of Antitumor Agents

The biosynthesis of the azabicyclic ring system of the azinomycin family of antitumor agents represents the “crown jewel” of the pathway and is a complex process involving at least 14 enzymatic steps. This study reports on the first biosynthetic step, the inroads, in the construction of the novel aziridino [1,2-<i>a</i>]­pyrrolidine, azabicyclic core, allowing us to support a new mechanism for azabicycle formation