Biosynthesis of the Antibiotic Echinosporin by a Novel Branch of the Shikimate Pathway

Marine life as a source for breast cancer treatment: A comprehensive review

Breast cancer, one of the most significant tumors among all cancer cells, still has deficiencies for effective treatment. Moreover, substitute treatments employing natural products as bioactive metabolites has been seriously considered. The source of bioactive metabolites are not only the most numerous but also represent the richest source. A unique source is from the oceans or marine species which demonstrated intriguing chemical and biological diversity which represents an astonishing reserve for discovering novel anticancer drugs. Notably, marine sponges produce the largest amount of diverse bioactive peptides, alkaloids, terpenoids, polyketides along with many secondary metabolites whose potential is mostly therapeutic. In this review, our main focus is on the marine derived secondary metabolites which demonstrated cytotoxic effects towards numerous breast cancer cells and have been isolated from the marine sources such as marine sponges, cyanobacteria, fungi, algae, tunicates, actinomycetes, ascidians, and other sources of marine organisms.

Proteomic analysis reveals the metabolic versatility of Amycolatopsis sp. BX17: A strain native from milpa agroecosystem soil

Amycolatopsis sp. BX17 is an actinobacterium isolated from milpa soils, which antagonizes the phytopathogenic fungus Fusarium graminearum. Metabolites secreted by the actinobacterium cultured in glucose-free medium inhibited 100% of the mycelial growth of F. graminearum RH1, while the inhibition rate was 65% in medium supplemented with 20 g/L glucose. With the aim of studying how the metabolism of strain BX17 is modulated by glucose as the main carbon source, media with 0 and 20 g/L glucose were selected to analyze the intracellular proteins by quantitative label-free proteomic analysis. Data are available via ProteomeXchange with identifier PXD028644. Proteins identified in bacteria cultured in medium without glucose were involved in glutamate metabolism, the Krebs cycle and the shikimate pathway, suggesting that amino acids are metabolized to synthesize antifungal compounds. In glucose-containing medium, carbon flux was directed mainly toward the synthesis of energy and cell growth. This study shows the metabolic versatility of Amycolatopsis BX17, and strengthens its potential use in designing biotechnological strategies for phytopathogen control. SIGNIFICANCE: Amycolatopsis BX17 is a bacterium isolated from milpa agroecosystems that antagonizes the phytopathogenic fungus Fusarium graminearum. Currently, there is scarce information about the metabolism involved in the biosynthesis of antifungal agents by this genus. We used a label-free proteomic approach to identify the differences in metabolic routes for antifungal biosynthesis in Amycolatopsis BX17 grown in media with 0 and 20 g/L glucose. Taken together the results suggest that the BX17 strain could be synthesizing the antifungal metabolite(s) from the Shikimate pathway through the synthesis and degradation of the amino acid tyrosine, which is a known precursor of glycopeptides with antibiotic and antifungal activity. While the lower antifungal activity of the metabolites secreted by Amycolatopsis BX17 when grown in a medium with glucose as the main carbon source, may be correlated with a lower synthesis of antifungal compounds, due to the directing of carbon flux toward metabolic pathways involved with energy synthesis and cell growth. Likewise, it is possible that the bacteria synthesize other compounds with biological activity, such as glycopeptides with antibiotic activity. These findings are relevant because they represent the first stage to understand the metabolic regulation involved in the biosynthesis of antifungal metabolites by the genus Amycolatopsis. Finally, improving our understanding of the metabolic regulation involved in the biosynthesis of antifungal metabolites is essential to design of strategies in agricultural biotechnology for phytopathogen control.

Chorismate- and isochorismate converting enzymes: versatile catalysts acting on an important metabolic node

Chorismate and isochorismate represent an important branching point connecting primary and secondary metabolism in bacteria, fungi, archaea and plants. Chorismate- and isochorismate-converting enzymes are potential targets for new bioactive compounds, as well as valuable biocatalysts for the in vivo and in vitro synthesis of fine chemicals. The diversity of the products of chorismate- and isochorismate-converting enzymes is reflected in the enzymatic three-dimensional structures and molecular mechanisms. Due to the high reactivity of chorismate and its derivatives, these enzymes have evolved to be accurately tailored to their respective reaction; at the same time, many of them exhibit a fascinating flexibility regarding side reactions and acceptance of alternative substrates. Here, we give an overview of the different (sub)families of chorismate- and isochorismate-converting enzymes, their molecular mechanisms, and three-dimensional structures. In addition, we highlight important results of mutagenetic approaches that generate a broader understanding of the influence of distinct active site residues for product formation and the conversion of one subfamily into another. Based on this, we discuss to what extent the recent advances in the field might influence the general mechanistic understanding of chorismate- and isochorismate-converting enzymes. Recent discoveries of new chorismate-derived products and pathways, as well as biocatalytic conversions of non-physiological substrates, highlight how this vast field is expected to continue developing in the future.

Amycolasporins and Dibenzoyls from Lichen-Associated Amycolatopsis hippodromi and Their Antibacterial and Anti-inflammatory Activities

Eleven metabolites, six echinosporins (1-6), four dibenzoyls (7-10), and an aromatic compound (11), were isolated from the fermentation broth of lichen-associated Amycolatopsis hippodromi. The structures of the new compounds (1-5, 8-11) were elucidated by comprehensive spectroscopic analysis including data from experimental and calculated ECD spectra. Amycolasporins A-C (1-3) demonstrated antibacterial activities against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli with MIC values of 25 or 100 μg/mL. Amycolasporin C (3) and the known dibenzoyl (7) attenuated the production of NO due to the suppression of the expression of nitric oxide synthase (iNOS) in LPS-induced RAW 264.7 cells in a dose-dependent manner.

Echinosporin antibiotics isolated from Amycolatopsis strain and their antifungal activity against root-rot pathogens of the Panax notoginseng

Actinomycete strain YIM PH20520, isolated from the rhizosphere soil sample of Panax notoginseng collected in Wenshang, Yunnan Province, China, exhibited antifungal activity against root-rot pathogens of the Panax notoginseng. The structures of bioactive molecules, isolated from the ethyl acetate extract of the fermentation broth of the strain, were identified as echinosporin (1) and 7-deoxyechinosporin (2) based on extensive spectroscopic analyses. 1 exhibited antifungal activity against four tested root-rot pathogens of Panax notoginseng include Fusarium oxysporum, Fusarium solani, Alternaria panax, and Phoma herbarum with the MIC value at 64, 64, 32, and 64 μg/mL, respectively. 2 exhibited antifungal activities against F. oxysporum, F. solani, A. panax, and P. herbarum with the MIC value at 128, 128, 64, and 128 μg/mL, respectively. Based on the phylogenetic analyses, the closest phylogenetic relative of strain YIM PH20520 is Amycolatopsis speibonae JS72^T (97.69%), so strain YIM PH20520 was identified as Amycolatopsis strain. To the best of our knowledge, this is the first report of echinosporin antibiotics isolated from Amycolatopsis strain besides Streptomyces strain and their antifungal activity against four tested root-rot pathogens of the Panax notoginseng. The results provide a reliable evidence for the following related biosynthetic investigations on Amycolatopsis strain YIM PH20520 due to echinosporins antibiotics' unique tricyclic acetal-lactone structures.

Antitumor compounds from marine actinomycetes

Chemotherapy is one of the main treatments used to combat cancer. A great number of antitumor compounds are natural products or their derivatives, mainly produced by microorganisms. In particular, actinomycetes are the producers of a large number of natural products with different biological activities, including antitumor properties. These antitumor compounds belong to several structural classes such as anthracyclines, enediynes, indolocarbazoles, isoprenoides, macrolides, non-ribosomal peptides and others, and they exert antitumor activity by inducing apoptosis through DNA cleavage mediated by topoisomerase I or II inhibition, mitochondria permeabilization, inhibition of key enzymes involved in signal transduction like proteases, or cellular metabolism and in some cases by inhibiting tumor-induced angiogenesis. Marine organisms have attracted special attention in the last years for their ability to produce interesting pharmacological lead compounds.

Echinosporins as new cell cycle inhibitors and apoptosis inducers from marine-derived Streptomyces albogriseolus

Bioassay-guided fractionation of the ethyl acetate extract from the fermentation broth of marine-derived Streptomyces albogriseolus A2002 led to the isolation of echinosporin (1) and 7-deoxyechinosporin (2). Compound 1 inhibited the proliferation of tsFT210, K562 and HCT-15 cancer cells (IC(50) 91.5 microM, 25.1 microM and 247 microM respectively) and 2 showed the same effect on K562 cells (IC(50) 143 microM). Flow cytometric analysis suggested that 1 and 2 exert their anti-proliferative effects on those cells through inhibiting cell cycle at the G(2)/M phase and inducing apoptosis.