Identification of a C-Glycosyltransferase Involved in Medermycin Biosynthesis

Advances in glycosyltransferase-mediated glycodiversification of small molecules

Currently, numerous glycosides have been synthesized and used in clinical applications, neutraceuticals, cosmetics, and food processing. Structurally, a glycoside is composed of aglycone attaching to one or several sugar moieties so-called glycone. It is found that biochemical or biopharmaceutical properties of glycoside are mainly determined by its sugar part and thereby alternation of this glycone resulting in novel structure and characteristics as well. The use of traditional production methods of glycosides such as direct extraction and purification from plants, animals, or microorganisms is very challenging (laborious, time-consuming, technique, high price, low yield, etc.). Alternatively, the use of enzymatic methods for the biosynthesis of glycosides has become a highly promising tool. Particularly, the diverse structure of glycosides can be obtained using the promiscuous catalytic activity of glycosyltransferases (GT) mined from bioresources (plants, fungi, microorganisms, etc.). In addition, the exploration of GT catalytic promiscuity toward diverse aglycones, and glycones has indeed been interesting and played a key role in the production of novel glycosides. This review described the recent advances in glycosyltransferase-mediated glycodiversification of small molecules (flavonoids, steroids, terpenoids, etc.). Mostly, references were collected from 2014 to 2023.

Rubiflavin G, photorubiflavin G, and photorubiflavin E: Novel pluramycin derivatives from Streptomyces sp. W2061 and their anticancer activity against breast cancer cells

The pluramycin family of antibiotics comprises angucycline compounds derived from actinomycetes that possess anticancer and antibacterial properties. Pluramycins are structurally characterized by two aminoglycosides linked by a carbon-carbon bond next to the γ-pyrone angucycline backbone. Kidamycins (3, 4) and rubiflavins (6-9) were screened through liquid chromatography-mass spectrometry analysis of the crude extracts of Streptomyces sp. W2061, which was cultured in complex media under phosphate-limiting conditions. Newly isolated rubiflavin G (7) and photoactivated compounds (8, 9) were characterized using exhaustive 1D and 2D nuclear magnetic resonance analysis. The cytotoxicity of kidamycin (3), photokidamycin (4), and photorubiflavin G (8) was determined using two human breast cancer cell lines-MCF7 and MDA-MB-231. Compared to MCF7 cells, MDA-MB-231 cells were more sensitive to the active compounds, and photokidamycin (4) considerably inhibited MCF7 and MDA-MB-231 cell growth (IC50 = 3.51 and 0.66 μM, respectively).

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

UDP-Glycosyltransferases in Edible Fungi: Function, Structure, and Catalytic Mechanism

UDP-glycosyltransferases (UGTs) are the most studied glycosyltransferases, and belong to large GT1 family performing the key roles in antibiotic synthesis, the development of bacterial glycosyltransferase inhibitors, and in animal inflammation. They transfer the glycosyl groups from nucleotide UDP-sugars (UDP-glucose, UDP-galactose, UDP-xylose, and UDP-rhamnose) to the acceptors including saccharides, proteins, lipids, and secondary metabolites. The present review summarized the recent of UDP-glycosyltransferases, including their structures, functions, and catalytic mechanism, especially in edible fungi. The future perspectives and new challenges were also summarized to understand of their structure–function relationships in the future. The outputs in this field could provide a reference to recognize function, structure, and catalytic mechanism of UDP-glycosyltransferases for understanding the biosynthesis pathways of secondary metabolites, such as hydrocarbons, monoterpenes, sesquiterpene, and polysaccharides in edible fungi.

Complete genome sequencing and in silico genome mining reveal the promising metabolic potential in Streptomyces strain CS-7

Gram-positive Streptomyces bacteria can produce valuable secondary metabolites. Streptomyces genomes include huge unknown silent natural product (NP) biosynthetic gene clusters (BGCs), making them a potential drug discovery repository. To collect antibiotic-producing bacteria from unexplored areas, we identified Streptomyces sp. CS-7 from mountain soil samples in Changsha, P.R. China, which showed strong antibacterial activity. Complete genome sequencing and prediction in silico revealed that its 8.4 Mbp genome contains a total of 36 BGCs for NPs. We purified two important antibiotics from this strain, which were structurally elucidated to be mayamycin and mayamycin B active against Staphylococcus aureus. We identified functionally a BGC for the biosynthesis of these two compounds by BGC direct cloning and heterologous expression in Streptomyces albus. The data here supported this Streptomyces species, especially from unexplored habitats, having a high potential for new NPs.

Chimeric natural products derived from medermycin and the nature-inspired construction of their polycyclic skeletons

Medermycin, produced by Streptomyces species, represents a family of antibiotics with significant activity against Gram-positive pathogens. The biosynthesis of this family of natural products has been studied, and new skeletons related to medermycin have rarely been reported until recently. Herein, we report eight chimeric medermycin-type natural products with unusual polycyclic skeletons. The formation of these compounds features some key nonenzymatic steps, which inspired us to construct complex polycyclic skeletons via three efficient one-step reactions under mild conditions. This strategy was further developed to efficiently synthesize analogues for biological activity studies. The synthetic compounds, chimedermycins L and M, and sekgranaticin B, show potent antibacterial activity against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and methicillin-resistant Staphylococcus epidermidis. This work paves the way for understanding the nonenzymatic formation of complex natural products and using it to synthesize natural product derivatives.

Elucidation of the di-c-glycosylation steps during biosynthesis of the antitumor antibiotic, kidamycin

Kidamycins belong to the pluramycin family of antitumor antibiotics that contain di-C-glycosylated angucycline. Owing to its interesting biological activity, several synthetic derivatives of kidamycins are currently being developed. However, the synthesis of these complex structural compounds with unusual C-glycosylated residues is difficult. In the kidamycin-producing Streptomyces sp. W2061 strain, the genes encoding the biosynthetic enzymes responsible for the structural features of kidamycin were identified. Two glycosyltransferase-coding genes, kid7 and kid21, were found in the kidamycin biosynthetic gene cluster (BGC). Gene inactivation studies revealed that the subsequent glycosylation steps occurred in a sequential manner, in which Kid7 first attached N,N-dimethylvancosamine to the C10 position of angucycline aglycone, following which Kid21 transferred an anglosamine moiety to C8 of the C10-glycosylated angucycline. Therefore, this is the first report to reveal the sequential biosynthetic steps of the unique C-glycosylated amino-deoxyhexoses of kidamycin. Additionally, we confirmed that all three methyltransferases (Kid4, Kid9, and Kid24) present in this BGC were involved in the biosynthesis of these amino-deoxyhexoses, N,N-dimethylvancosamine and anglosamine. Aglycone compounds and the mono-C-glycosylated compound obtained in this process will be used as substrates for the development of synthetic derivatives in the future.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as pyrasplorine A from Aspergillus versicolor.