ABSTRACT
Polyketide synthase (PKS) derived natural products are biosynthesized by head-to-tail addition of acetate and malonate extender units resulting in linear extended-polyketide chains. Despite the well-documented structural diversity associated with PKS-derived natural products, C-C chain branching deviating from the usual linear pattern is relatively rare. Herein, type-II PKS angucyclic natural products containing a hemiaminal functionality were identified and proposed as the parent of a series of C-C-branched analogues. These C-C linked acetate or pyruvate branching units were located at the α-positions on the extended polyketide chains of jadomycins incorporating 3- and 4-aminomethylbenzoic acids. Labeling studies utilizing [1-13C]-d-glucose provided mechanistic evidence that the C-C bond formation occurred as a result of a previously unidentified post-PKS processing, additional to the enzymes encoded within the biosynthetic gene cluster. Selected compounds were evaluated in cytotoxic or antimicrobial assays.
Subject(s)
Antineoplastic Agents/pharmacology , Biological Products/pharmacology , Carbon/metabolism , Fibroblasts/drug effects , Gram-Positive Bacteria/drug effects , Polyketide Synthases/metabolism , Streptomyces/metabolism , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/metabolism , Biological Products/chemistry , Biological Products/metabolism , Carbon/chemistry , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Chlorocebus aethiops , Drug Screening Assays, Antitumor , Humans , Microbial Sensitivity Tests , Molecular Structure , Polyketide Synthases/chemistry , Vero CellsABSTRACT
Angucycline antibiotics are composed of a classical four-ring angularly linked polyaromatic backbone. Differential cyclization chemistry of the A- and B-rings in jadomycin biosynthesis led to the discovery of two new furan analogues, while oxidation led to a ring-opened form of the jadomycin Nε-trifluoroacetyl-l-lysine (TFAL) congener. The compounds were isolated from Streptomyces venezuelae ISP5230 cultures grown with TFAL. Biosynthetic incorporation using d-[1-13C]-glucose in cultures enabled the unambiguous assignment of the aldehyde, alcohol, and amide functionalities present in these new congeners through NMR spectroscopy. Tandem mass spectrometry analysis of cultures grown with 15Nα- or 15Nε-lysine demonstrated the incorporation of Nα exclusively into the angucycline backbone, contrasting results with ornithine [J. Am. Chem. Soc. 2015, 137, 3271]. Compounds were evaluated against antimicrobial and cancer cell panels and found to possess good activity against Gram-positive bacteria.
Subject(s)
Anti-Bacterial Agents/chemistry , Furans/chemistry , Isoquinolines/chemistry , Lactams/chemistry , Lysine/analogs & derivatives , Naphthoquinones/chemistry , Streptomyces/chemistry , Amino Acid Sequence , Cyclization , Gram-Positive Bacteria , Lysine/chemistry , Lysine/metabolism , Methicillin-Resistant Staphylococcus aureus/drug effects , Molecular Structure , Pseudomonas aeruginosa/drug effectsABSTRACT
The jadomycin-derived compound l-digitoxosyl-phenanthroviridin was isolated from fermentations of Streptomyces venezuelae ISP5230 grown in nutrient-deficient media with l-lysine as the sole nitrogen source. Structural elucidation was accomplished using a combination of high-resolution MS, LC-MS/MS, and 1D- and 2D-NMR. The compound was evaluated against the National Cancer Institute (NCI) 60 human tumor cell line screen in both the one-dose and five-dose screens, and cytotoxicity was compared to a small library of jadomycin analogues to probe the structure-activity relationship.