RESUMEN
Phenyl polyenes comprise a small family of bacterial natural products with broad and potent bioactivities, primarily found in actinobacteria. Here we report the discovery of five new phenyl polyene metabolites, maduraflavacins A-E (1-5), from a rare, marine-derived actinobacteria strain Actinomadura glauciflava NA03286. The structures of these natural products were determined by NMR spectroscopy, HRESIMS, LC-MS/MS, and chemical derivatization. All of these new maduraflavacins feature methyl substitutions at the polyene side chain, and maduraflavacins A-C (1-3) possessed a 1-N-ß-d-glucosamine-(3 â 1)-O-ß-d-glucopyranosyl-(3 â 1)-O-ß-d-glucopyranosyl-(6 â 1)-O-ß-d-glucopyranoside tetrasaccharide moiety via an amido linkage with a phenyl polyene skeleton. Compounds 1 and 2 showed weak antibacterial activities against the Gram-positive bacteria Staphylococcus aureus Sau 16339 and Micrococcus luteus, respectively.
RESUMEN
Cyclic peptides with cyclophane linkers are an attractive compound type owing to the fine-tuned rigid three-dimensional structures and unusual biophysical features. Cytochrome P450 enzymes are capable of catalyzing not only the C-C and C-O oxidative coupling reactions found in vancomycin and other nonribosomal peptides (NRPs), but they also exhibit novel catalytic activities to generate cyclic ribosomally synthesized and post-translationally modified peptides (RiPPs) through cyclophane linkage. To discover more P450-modified multicyclic RiPPs, we set out to find cryptic and unknown P450-modified RiPP biosynthetic gene clusters (BGCs) through genome mining. Synergized bioinformatic analysis reveals that P450-modified RiPP BGCs are broadly distributed in bacteria and can be classified into 11â classes. Focusing on two classes of P450-modified RiPP BGCs where precursor peptides contain multiple conserved aromatic amino acid residues, we characterized 11 novel P450-modified multicyclic RiPPs with different cyclophane linkers through heterologous expression. Further mutation of the key ring-forming residues and combinatorial biosynthesis study revealed the order of bond formation and the specificity of P450s. This study reveals the functional diversity of P450 enzymes involved in the cyclophane-containing RiPPs and indicates that P450 enzymes are promising tools for rapidly obtaining structurally diverse cyclic peptide derivatives.
Asunto(s)
Productos Biológicos , Ciclofanos , Péptidos/química , Péptidos Cíclicos/química , Biología Computacional/métodos , Sistema Enzimático del Citocromo P-450/metabolismo , Procesamiento Proteico-Postraduccional , Productos Biológicos/químicaRESUMEN
Sordarin (1) is a fungal diterpene glycoside that displays potent antifungal bioactivity through inhibition of elongation factor 2. The structures of sordarin and related compounds feature a highly rearranged tetracyclic diterpene core. In this study, we identified a concise pathway in the biosynthesis of sordarin. A diterpene cyclase (SdnA) generates the 5/8/5 cycloaraneosene framework, which is decorated by a set of P450s that catalyze a series of oxidation reactions, including hydroxylation, desaturation, and C-C bond oxidative cleavage, to give a carboxylate intermediate with a terminal alkene and a cyclopentadiene moiety. A novel Diels-Alderase SdnG catalyzes an intramolecular Diels-Alder (IMDA) reaction on this intermediate to forge the sordarin core structure. Subsequent methyl hydroxylation and glycosylation complete the biosynthesis of sordarin. Our work discloses a new strategy used by nature for the formation of the rearranged diterpene skeleton.
Asunto(s)
Diterpenos , Indenos , Diterpenos/química , Indenos/química , Norbornanos , EsqueletoRESUMEN
Four new compounds, asperisocoumarin G (1), asperisocoumarin H (2), (±)-asperisocoumarin I [(±)-3], along with the known pergillin (4) and penicisochroman L (5) were isolated from a mangrove endophytic fungus Aspergillus sp. 085242 by further chemical investigation. The structures of the new compounds, including their absolute configurations, were established by analysis of HR-ESI-MS and NMR spectroscopic data, and ECD calculation. Asperisocoumarins G-I (1-3) were new isocoumarins belonging to the class of furo[3, 2-h]isocoumarins which are rarely found in natural sources. All of the isolated compounds were evaluated for their α-glucosidase inhibitory effects, and compounds 1 and 4 showed moderate α-glucosidase inhibitory activity, respectively. In an antimicrobial test, the racemate of 3 showed antibacterial activity against Salmonella.