Gelastatins, new inhibitors of matrix metalloproteinases from Westerdykella multispora F50733

Westerdykella reniformis sp. nov., producing the antibiotic metabolites melinacidin IV and chetracin B

Westerdykella reniformis Ebead & Overy sp. nov. is described based on morphology and phylogenetic analyses using ITS, nLSU rDNA, and β-tubulin gene sequences. Westerdykella reniformis is characterized by the production of cleistothecioid ascomata, containing small globose to subglobose asci with 32, aseptate, dark colored, pronouncedly reniform ascospores having a concave central groove. The isolate was obtained from a red alga (Polysiphonia sp.) collected from the tidal zone in Canada at low tide. Organic extracts enriched in extrolites, obtained from fermentation on a rice-based media, inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), S. warneri, and Proteus vulgaris. Presented here is the identification of the compounds responsible for the observed antimicrobial activity, the taxonomic description of W. reniformis, and a dichotomous key to the known species of Westerdykella based on macro- and micromorphological characters.

Molecular modeling of non-covalent binding of homochiral (3S,3′S)-astaxanthin to matrix metalloproteinase-13 (MMP-13)

Inhibitors for matrix metalloproteinases (MMPs) are under investigation for the treatment of various important chronic illnesses, including cancer, arthritis, and cardiovascular disease (CVD). In particular, MMP-13 is currently being probed as a potential key target in CVD and malignant disease due to its documented effects on extracellular matrix (ECM) remodeling, important in the pathophysiology of these diseases. Within the family of related mammalian MMP enzymes, MMP-13 possesses a large hydrophobic binding pocket relative to that of other MMPs. Homochiral astaxanthin (3S,3'S-AST; 3S,3'S-dihydroxy-beta,beta-carotene-4,4'-dione), an important antioxidant and anti-inflammatory xanthophyll carotenoid, is an active metabolite of several novel soft drugs in clinical development; it is also extensively used and tested as a human nutraceutical. In the current study, the prediction of the geometry and energetics of its binding to human MMP-13 was conducted with molecular modeling. The method used was found to predict the energy of binding of known ligands of MMP-13 with great precision. Blind docking using the whole protein target was then used in order to identify the possible binding site(s) of AST. AST was predicted to bind at several sites in close proximity to the active center. Subsequent analyses focused on the binding site at the atomic (i.e., amino acid sequence) level suggested that AST can bind to MMP-13 with high affinity and favorable energetics. Therefore, the modeling study predicts potential direct enzyme-inhibitory activity of AST against MMP-13, a behavior that may be exploited in mammalian systems in which pathological upregulation of MMP activity is paramount.

Dykellic acid inhibits drug-induced caspase-3-like protease activation

Dykellic acid is a novel microbial metabolite isolated from the broth of Westerdykella multispora F50733. Investigations on the molecular function of dykellic acid revealed that this compound partially inhibits calcium influx, resulting in a decrease in Ca(2+)-dependent endonuclease activation and DNA fragmentation induced by camptothecin. In our experiments, active caspase-3-like protease cleavage of procaspase-3, PARP, and cytosolic cytochrome c was inhibited by dykellic acid in a concentration-dependent manner when the apoptosis was induced by camptothecin as well as doxorubicin. We confirmed that dykellic acid did not bind to camptothecin using surface plasmon resonance analysis. These results suggest that dykellic acid inhibits drug-induced apoptosis via a caspase-3-like protease-suppressing mechanism. Our data provide important information on the mechanism of action of dykellic acid and indicate that this compound may be employed in the treatment of specific caspase-3-like protease-mediated diseases.