Harnessing the Synthetic Capabilities of Glycopeptide Antibiotic Tailoring Enzymes: Characterization of the UK-68,597 Biosynthetic Cluster

Actinoplanes kirromycinicus sp. nov., isolated from soil

A novel actinomycete, designated as TPMA0078T, was isolated from a soil sample collected in Shinjuku, Tokyo, Japan. 16S rRNA gene sequence analysis indicated that strain TPMA0078T belongs to the genus Actinoplanes and is closely related to Actinoplanes regularis IFO 12514T (99.86% 16S rRNA gene sequence similarity). The spores of strain TPMA0078T were motile, and the sporangia were cylindrical. The diamino acids in the cell wall peptidoglycan of strain TPMA0078T were meso-diaminopimelic acid and 3OH-meso-diaminopimelic acid. Whole-cell sugars were glucose and mannose, with galactose as a minor component. The major cellular fatty acids identified were iso-C15:0, iso-C16:0, and anteiso-C17:0. The predominant menaquinone was MK-9(H4), and the principal polar lipid was phosphatidylethanolamine. These chemotaxonomic properties of strain TPMA0078T were consistent with those of Actinoplanes. Meanwhile, digital DNA-DNA hybridization and average nucleotide identity values showed low relatedness between strain TPMA0078T and A. regularis NBRC 12514T. Furthermore, several phenotypic properties of strain TPMA0078T distinguished it from those of closely related species. Based on its genotypic and phenotypic characteristics, strain TPMA0078T represents a novel species of the genus Actinoplanes, for which the name Actinoplanes kirromycinicus sp. nov. is proposed. The type strain is TPMA0078T (=NBRC 116422T = TBRC 18262T).

The Impact of Heterologous Regulatory Genes from Lipodepsipeptide Biosynthetic Gene Clusters on the Production of Teicoplanin and A40926

StrR-like pathway-specific transcriptional regulators (PSRs) function as activators in the biosynthesis of various antibiotics, including glycopeptides (GPAs), aminoglycosides, aminocoumarins, and ramoplanin-like lipodepsipeptides (LDPs). In particular, the roles of StrR-like PSRs have been previously investigated in the biosynthesis of streptomycin, novobiocin, GPAs like balhimycin, teicoplanin, and A40926, as well as LDP enduracidin. In the current study, we focused on StrR-like PSRs from the ramoplanin biosynthetic gene cluster (BGC) in Actinoplanes ramoplaninifer ATCC 33076 (Ramo5) and the chersinamycin BGC in Micromonospora chersina DSM 44151 (Chers28). Through the analysis of the amino acid sequences of Ramo5 and Chers28, we discovered that these proteins are phylogenetically distant from other experimentally investigated StrR PSRs, although all StrR-like PSRs found in BGCs for different antibiotics share a conserved secondary structure. To investigate whether Ramo5 and Chers28, given their phylogenetic positions, might influence the biosynthesis of other antibiotic pathways governed by StrR-like PSRs, the corresponding genes (ramo5 and chers28) were heterologously expressed in Actinoplanes teichomyceticus NRRL B-16726 and Nonomuraea gerenzanensis ATCC 39727, which produce the clinically-relevant GPAs teicoplanin and A40926, respectively. Recombinant strains of NRRL B-16726 and ATCC 39727 expressing chers28 exhibited improved antibiotic production, although the expression of ramo5 did not yield the same effect. These results demonstrate that some StrR-like PSRs can "cross-talk" between distant biosynthetic pathways and might be utilized as tools for the activation of silent BGCs regulated by StrR-like PSRs.

Actinoplanes oblitus sp. nov., producing the glycopeptide antibiotic A477

In 1973, Eli Lilly and Company described the filamentous actinomycete producing the glycopeptide antibiotic A477 as an Actinoplanes species on the basis of its morphological and physiological features and deposited it as NRRL 3884T. In this paper, we report that the phylogenetic analysis based on the 16S rRNA gene sequence and the whole genome phylogenomic study indicate that NRRL 3884T forms a distinct monophyletic line within the genus Actinoplanes, being most closely related to Actinoplanes octamycinicus NBRC 14524T [99.6 % 16S rRNA gene similarity, 89.4 % average nucleotide identity (ANI), 46.0 % digital DNA-DNA hybridization (dDDH)] and Actinoplanes ianthinogenes NBRC 13996T (98.8 % 16S rRNA gene similarity, 89.0 % ANI, 47.0 % dDDH). NRRL 3884T forms an extensively branched, non-fragmented vegetative mycelium; either sterile aerial hyphae or regular subglobose sporangia are formed depending on cultivation conditions. The cell wall contains meso-2,6-diaminopimelic acid and 2,6-diamino-3-hydroxypimelic acid and the diagnostic sugars are glucose, mannose and ribose with a minor amount of rhamnose. The predominant menaquinone (MK) is MK-9(H4), with minor amounts of MK-9(H2), MK-9(H6) and MK-9(H8). Mycolic acids are absent. The diagnostic phospholipids are diphosphatidylglycerol and phosphatidylethanolamine. The major cellular fatty acids are anteiso-C17 : 0, iso-C16 : 0 and iso-C15 : 0, with moderate amounts of anteiso-C15 : 0 and iso-C17 : 0. The genomic G+C content is 71.5 mol%. Significant differences in the genomic, morphological, chemotaxonomic and biochemical data between NRRL 3884T and the two most closely related Actinoplanes type strains clearly demonstrate that NRRL 3884T represents a novel species of the genus Actinoplanes, for which the name Actinoplanes oblitus sp. nov. is proposed. The type strain is NRRL 3884T (=DSM 116196T).

Newest perspectives of glycopeptide antibiotics: biosynthetic cascades, novel derivatives, and new appealing antimicrobial applications

Glycopeptide antibiotics (GPAs) are a family of non-ribosomal peptide natural products with polypeptide skeleton characteristics, which are considered the last resort for treating severe infections caused by multidrug-resistant Gram-positive pathogens. Over the past few years, an increasing prevalence of Gram-positive resistant strain "superbugs" has emerged. Therefore, more efforts are needed to study and modify the GPAs to overcome the challenge of superbugs. In this mini-review, we provide an overview of the complex biosynthetic gene clusters (BGCs), the ingenious crosslinking and tailoring modifications, the new GPA derivatives, the discoveries of new natural GPAs, and the new applications of GPAs in antivirus and anti-Gram-negative bacteria. With the development and interdisciplinary integration of synthetic biology, next-generation sequencing (NGS), and artificial intelligence (AI), more GPAs with new chemical structures and action mechanisms will constantly be emerging.

Genetics Behind the Glycosylation Patterns in the Biosynthesis of Dalbaheptides

Glycopeptide antibiotics are valuable natural metabolites endowed with different pharmacological properties, among them are dalbaheptides used to treat different infections caused by multidrug-resistant Gram-positive pathogens. Dalbaheptides are produced by soil-dwelling high G-C Gram-positive actinobacteria. Their biosynthetic pathways are encoded within large biosynthetic gene clusters. A non-ribosomally synthesized heptapeptide aglycone is the common scaffold for all dalbaheptides. Different enzymatic tailoring steps, including glycosylation, are further involved in decorating it. Glycosylation of dalbaheptides is a crucial step, conferring them specific biological activities. It is achieved by a plethora of glycosyltransferases, encoded within the corresponding biosynthetic gene clusters, able to install different sugar residues. These sugars might originate from the primary metabolism, or, alternatively, their biosynthesis might be encoded within the biosynthetic gene clusters. Already installed monosaccharides might be further enzymatically modified or work as substrates for additional glycosylation. In the current minireview, we cover recent updates concerning the genetics and enzymology behind the glycosylation of dalbaheptides, building a detailed and consecutive picture of this process and of its biological evolution. A thorough understanding of how glycosyltransferases function in dalbaheptide biosynthesis might open new ways to use them in chemo-enzymatic synthesis and/or in combinatorial biosynthesis for building novel glycosylated antibiotics.

Genomic Insights into the Distribution and Phylogeny of Glycopeptide Resistance Determinants within the Actinobacteria Phylum

The spread of antimicrobial resistance (AMR) creates a challenge for global health security, rendering many previously successful classes of antibiotics useless. Unfortunately, this also includes glycopeptide antibiotics (GPAs), such as vancomycin and teicoplanin, which are currently being considered last-resort drugs. Emerging resistance towards GPAs risks limiting the clinical use of this class of antibiotics-our ultimate line of defense against multidrug-resistant (MDR) Gram-positive pathogens. But where does this resistance come from? It is widely recognized that the GPA resistance determinants-van genes-might have originated from GPA producers, such as soil-dwelling Gram-positive actinobacteria, that use them for self-protection. In the current work, we present a comprehensive bioinformatics study on the distribution and phylogeny of GPA resistance determinants within the Actinobacteria phylum. Interestingly, van-like genes (vlgs) were found distributed in different arrangements not only among GPA-producing actinobacteria but also in the non-producers: more than 10% of the screened actinobacterial genomes contained one or multiple vlgs, while less than 1% encoded for a biosynthetic gene cluster (BGC). By phylogenetic reconstructions, our results highlight the co-evolution of the different vlgs, indicating that the most diffused are the ones coding for putative VanY carboxypeptidases, which can be found alone in the genomes or associated with a vanS/R regulatory pair.

Glycopeptide Antibiotic Resistance Genes: Distribution and Function in the Producer Actinomycetes

Glycopeptide antibiotics (GPAs) are considered drugs of "last resort" for the treatment of life-threatening infections caused by relevant Gram-positive pathogens (enterococci, staphylococci, and clostridia). Driven by the issue of the never-stopping evolution of bacterial antibiotic resistance, research on GPA biosynthesis and resistance is developing fast in modern "post-genomic" era. It is today widely accepted that resistance mechanisms emerging in pathogens have been acquired from the soil-dwelling antibiotic-producing actinomycetes, which use them to avoid suicide during production, rather than being orchestrated de novo by pathogen bacteria upon continued treatment. Actually, more and more genomes of GPA producers are being unraveled, carrying a broad collection of differently arranged GPA resistance (named van) genes. In the producer actinomycetes, van genes are generally associated with the antibiotic biosynthetic gene clusters (BGCs) deputed to GPA biosynthesis, being probably transferred/arranged together, favoring a possible co-regulation between antibiotic production and self-resistance. GPA BGC-associated van genes have been also found mining public databases of bacterial genomic and metagenomic sequences. Interestingly, some BGCs for antibiotics, seemingly unrelated to GPAs (e.g., feglymycin), carry van gene homologues. Herein, we would like to cover the recent advances on the distribution of GPA resistance genes in genomic and metagenomics datasets related to GPA potential/proved producer microorganisms. A thorough understanding of GPA resistance in the producing microorganisms may prove useful in the future surveillance of emerging mechanisms of resistance to this clinically relevant antibiotic class.

Teicoplanin biosynthesis: unraveling the interplay of structural, regulatory, and resistance genes

Teicoplanin (Tcp) is a clinically relevant glycopeptide antibiotic (GPA) that is produced by the actinobacterium Actinoplanes teichomyceticus. Tcp is a front-line therapy for treating severe infections caused by multidrug-resistant Gram-positive pathogens in adults and infants. In this review, we provide a detailed overview of how Tcp is produced by A. teichomyceticus by describing Tcp biosynthesis, regulation, and resistance. We summarize the knowledge gained from in vivo and in vitro studies to provide an integrated model of teicoplanin biosynthesis. Then, we discuss genetic and nutritional factors that contribute to the regulation of teicoplanin biosynthesis, focusing on those that have been successfully applied for improving teicoplanin production. A current view on teicoplanin self-resistance mechanisms in A. teichomyceticus is given, and we compare the Tcp biosynthetic gene cluster with other glycopeptide gene clusters from actinoplanetes and from unidentified isolates/metagenomics samples. Finally, we provide an outlook for further directions in studying Tcp biosynthesis and regulation.

New Molecular Tools for Regulation and Improvement of A40926 Glycopeptide Antibiotic Production in Nonomuraea gerenzanensis ATCC 39727

Genome sequencing has revealed that Nonomuraea spp. represent a still largely unexplored source of specialized metabolites. Nonomuraea gerenzanensis ATCC 39727 is the most studied representative species since it produces the glycopeptide antibiotic (GPA) A40926 – the precursor of the clinically relevant antibiotic dalbavancin, approved by the FDA in 2014 for the treatment of acute skin infections caused by multi-drug resistant Gram-positive pathogens. The clinical relevance of dalbavancin has prompted increased attention on A40926 biosynthesis and its regulation. In this paper, we investigated how to enhance the genetic toolkit for members of the Nonomuraea genus, which have proved quite recalcitrant to genetic manipulation. By constructing promoter-probe vectors, we tested the activity of 11 promoters (heterologous and native) using the GusA reporter system in N. gerenzanensis and in Nonomuraea coxensis; this latter species is phylogenetically distant from N. gerenzanesis and also possesses the genetic potential to produce A40926 or a very similar GPA. Finally, the strongest constitutive promoter analyzed in this study, aac(3)IVp, was used to overexpress the cluster-situated regulatory genes controlling A40926 biosynthesis (dbv3 and dbv4 from N. gerenzanensis and nocRI from N. coxensis) in N. gerenzanensis, and the growth and productivity of the best performing strains were assessed at bioreactor scale using an industrial production medium. Overexpression of positive pathway-specific regulatory genes resulted in a significant increase in the level of A40926 production in N. gerenzanensis, providing a new knowledge-based approach to strain improvement for this valuable glycopeptide antibiotic.

Regulation of teicoplanin biosynthesis: refining the roles of tei cluster-situated regulatory genes

Teicoplanin is a frontline glycopeptide antibiotic produced by Actinoplanes teichomyceticus. It is used to treat complicated cases of infection, including pediatric ones, caused by Gram-positive pathogens. There is a steady interest in elucidating the genetic mechanisms determining teicoplanin production, as they would help overproduce known teicoplanins and discover novel glycopeptides. Herein, we investigate the transcriptional organization of the tei biosynthetic gene cluster and the roles of the cluster-situated regulatory genes in controlling teicoplanin production and self-resistance in A. teichomyceticus. We demonstrate that the tei cluster is organized into nine polygenic and nine monogenic transcriptional units. Most of tei biosynthetic genes are subjected to StrR-like Tei15* control, which, in turn, appears to be regulated by LuxR-type Tei16*. Expression of the genes conferring teicoplanin self-resistance in A. teichomyceticus is not co-regulated with antibiotic production. The gene tei31*, coding for a putative DNA binding protein, is not expressed under teicoplanin producing conditions and is dispensable for antibiotic production. Finally, phylogenesis reconstruction of the glycopeptide cluster-encoded regulators reveals two main clades of StrR-like regulators. Tei15* and close orthologues form one of these clades; the second clade is composed by orthologues of Bbr and Dbv4, governing the biosynthesis of balhimycin and teicoplanin-like A40926, respectively. In addition, the LuxR-type Tei16* appears unrelated to the LuxR-like Dbv3, which is controlling A40926 biosynthesis. Our results shed new light on teicoplanin biosynthesis regulation and on the evolution of novel and old glycopeptide biosynthetic gene clusters.

Trichlorination of a Teicoplanin-Type Glycopeptide Antibiotic by the Halogenase StaI Evades Resistance

Glycopeptide antibiotics (GPAs) include clinically important drugs used for the treatment of infections caused by Gram-positive pathogens. These antibiotics are specialized metabolites produced by several genera of actinomycete bacteria. While many GPAs are highly chemically modified, A47934 is a relatively unadorned GPA lacking sugar or acyl modifications, common to other members of the class, but which is chlorinated at three distinct sites. The biosynthesis of A47934 is encoded by a 68-kb gene cluster in Streptomyces toyocaensis NRRL 15009. The cluster includes all necessary genes for the synthesis of A47934, including two predicted halogenase genes, staI and staK In this study, we report that only one of the halogenase genes, staI, is necessary and essential for A47934 biosynthesis. Chlorination of the A47934 scaffold is important for antibiotic activity, as assessed by binding affinity for the target N-acyl-d-Ala-d-Ala. Surprisingly, chlorination is also vital to avoid activation of enterococcal and Streptomyces VanB-type GPA resistance through induction of resistance genes. Phenotypic assays showed stronger induction of GPA resistance by the dechlorinated compared to the chlorinated GPA. Correspondingly, the relative expression of the enterococcal vanA resistance gene was shown to be increased by the dechlorinated compared to the chlorinated compound. These results provide insight into the biosynthesis of GPAs and the biological function of GPA chlorination for this medically important class of antibiotic.

Developments in Glycopeptide Antibiotics

Glycopeptide antibiotics (GPAs) are a key weapon in the fight against drug resistant bacteria, with vancomycin still a mainstream therapy against serious Gram-positive infections more than 50 years after it was first introduced. New, more potent semisynthetic derivatives that have entered the clinic, such as dalbavancin and oritavancin, have superior pharmacokinetic and target engagement profiles that enable successful treatment of vancomycin-resistant infections. In the face of resistance development, with multidrug resistant (MDR) S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) together causing 20-fold more infections than all MDR Gram-negative infections combined, further improvements are desirable to ensure the Gram-positive armamentarium is adequately maintained for future generations. A range of modified glycopeptides has been generated in the past decade via total syntheses, semisynthetic modifications of natural products, or biological engineering. Several of these have undergone extensive characterization with demonstrated in vivo efficacy, good PK/PD profiles, and no reported preclinical toxicity; some may be suitable for formal preclinical development. The natural product monobactam, cephalosporin, and β-lactam antibiotics all spawned multiple generations of commercially and clinically successful semisynthetic derivatives. Similarly, next-generation glycopeptides are now technically well positioned to advance to the clinic, if sufficient funding and market support returns to antibiotic development.

Complex Regulatory Networks Governing Production of the Glycopeptide A40926

Glycopeptides (GPAs) are an important class of antibiotics, with vancomycin and teicoplanin being used in the last 40 years as drugs of last resort to treat infections caused by Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus. A few new GPAs have since reached the market. One of them is dalbavancin, a derivative of A40926 produced by the actinomycete Nonomuraea sp. ATCC 39727, recently classified as N. gerenzanensis. This review summarizes what we currently know on the multilevel regulatory processes governing production of the glycopeptide A40926 and the different approaches used to increase antibiotic yields. Some nutrients, e.g., valine, l-glutamine and maltodextrin, and some endogenous proteins, e.g., Dbv3, Dbv4 and RpoB^R, have a positive role on A40926 biosynthesis, while other factors, e.g., phosphate, ammonium and Dbv23, have a negative effect. Overall, the results available so far point to a complex regulatory network controlling A40926 in the native producing strain.

Old and new glycopeptide antibiotics: From product to gene and back in the post-genomic era

Glycopeptide antibiotics are drugs of last resort for treating severe infections caused by multi-drug resistant Gram-positive pathogens. First-generation glycopeptides (vancomycin and teicoplanin) are produced by soil-dwelling actinomycetes. Second-generation glycopeptides (dalbavancin, oritavancin, and telavancin) are semi-synthetic derivatives of the progenitor natural products. Herein, we cover past and present biotechnological approaches for searching for and producing old and new glycopeptide antibiotics. We review the strategies adopted to increase microbial production (from classical strain improvement to rational genetic engineering), and the recent progress in genome mining, chemoenzymatic derivatization, and combinatorial biosynthesis for expanding glycopeptide chemical diversity and tackling the never-ceasing evolution of antibiotic resistance.

Biosynthesis of therapeutic natural products using synthetic biology

Natural products are a group of bioactive structurally diverse chemicals produced by microorganisms and plants. These molecules and their derivatives have contributed to over a third of the therapeutic drugs produced in the last century. However, over the last few decades traditional drug discovery pipelines from natural products have become far less productive and far more expensive. One recent development with promise to combat this trend is the application of synthetic biology to therapeutic natural product biosynthesis. Synthetic biology is a young discipline with roots in systems biology, genetic engineering, and metabolic engineering. In this review, we discuss the use of synthetic biology to engineer improved yields of existing therapeutic natural products. We further describe the use of synthetic biology to combine and express natural product biosynthetic genes in unprecedented ways, and how this holds promise for opening up completely new avenues for drug discovery and production.

How To Make a Glycopeptide: A Synthetic Biology Approach To Expand Antibiotic Chemical Diversity

Modification of natural product backbones is a proven strategy for the development of clinically useful antibiotics. Such modifications have traditionally been achieved through medicinal chemistry strategies or via in vitro enzymatic activities. In an orthogonal approach, engineering of biosynthetic pathways using synthetic biology techniques can generate chemical diversity. Here we report the use of a minimal teicoplanin class glycopeptide antibiotic (GPA) scaffold expressed in a production-optimized Streptomyces coelicolor strain to expand GPA chemical diversity. Thirteen scaffold-modifying enzymes from 7 GPA biosynthetic gene clusters in different combinations were introduced into S. coelicolor, enabling us to explore the criteria for in-cell GPA modification. These include identifying specific isozymes that tolerate the unnatural GPA scaffold and modifications that prevent or allow further elaboration by other enzymes. Overall, 15 molecules were detected, 9 of which have not been reported previously. Some of these compounds showed activity against GPA-resistant bacteria. This system allows us to observe the complex interplay between substrates and both non-native and native tailoring enzymes in a cell-based system and establishes rules for GPA synthetic biology and subsequent expansion of GPA chemical diversity.

Recent advances in engineering nonribosomal peptide assembly lines

Nonribosomal peptides are amongst the most widespread and structurally diverse secondary metabolites in nature with many possessing bioactivity that can be exploited for therapeutic applications. Due to the major challenges associated with total- and semi-synthesis, bioengineering approaches have been developed to increase yields and generate modified peptides with improved physicochemical properties or altered bioactivity. Here we review the major advances that have been made over the last decade in engineering the biosynthesis of nonribosomal peptides. Structural diversity has been introduced by the modification of enzymes required for the supply of precursors or by heterologous expression of tailoring enzymes. The modularity of nonribosomal peptide synthetase (NRPS) assembly lines further supports module or domain swapping methodologies to achieve changes in the amino acid sequence of nonribosomal peptides. We also review the new synthetic biology technologies promising to speed up the process, enabling the creation and optimisation of many more assembly lines for heterologous expression, offering new opportunities for engineering the biosynthesis of novel nonribosomal peptides.

Evolving medicinal chemistry strategies in antibiotic discovery

Chemical modification of synthetic or natural product antibiotic scaffolds to expand potency and spectrum and to bypass mechanisms of resistance has dominated antibiotic drug discovery and proven immensely successful. However, the inexorable evolution of drug resistance coupled with a drought in innovation in antibiotic discovery contribute to a dearth of new drugs entering to market. Better understanding of the physicochemical properties of antibiotic chemical space is required to inform new antibiotic discovery. Innovations such as the development of antibiotic adjuvants to preserve efficacy of existing drugs together with expanding antibiotic chemical diversity through synthetic biology or new techniques to mine antibiotic producing organisms, are required to bridge the growing gap between the need for new drugs and their discovery.

Draft Genome Sequence of an Endophytic Actinoplanes Species, Encoding Uncommon trans-Acyltransferase Polyketide Synthases

Actinoplanes is an endophytic actinobacterium isolated from the medicinal plant Amphipterygium adstringens. The strain draft genome sequence reveals a gene cluster involved in the biosynthesis of a hybrid trans-acyltransferase (AT) polyketide, an unconventional bioactive metabolite never reported before in the genus Actinoplanes.

Bioprospecting potential of halogenases from Arctic marine actinomycetes

Background

Halometabolites, an important group of natural products, generally require halogenases for their biosynthesis. Actinomycetes from the Arctic Ocean have rarely been investigated for halogenases and their gene clusters associated, albeit great potential of halometabolite production has been predicted. Therefore, we initiated this research on the screening of halogenases from Arctic marine actinomycetes isolates to explore their genetic potential of halometabolite biosynthesis.

Results

Nine halogenase genes were discovered from sixty Arctic marine actinomycetes using in-house designed or previously reported PCR primers. Four representative genotypes were further cloned to obtain full coding regions through genome walking. The resulting halogenases were predicted to be involved in halogenation of indole groups, antitumor agent ansamitocin-like substrates, or unknown peptide-like compounds. Genome sequencing revealed a potential gene cluster containing the halogenase predicted to catalyze peptide-like compounds. However, the gene cluster was probably silent under the current conditions.

Conclusions

PCR-based screening of halogenase genes is a powerful and efficient tool to conduct bioprospecting of halometabolite-producing actinomycetes from the Arctic. Genome sequencing can also identify cryptic gene clusters potentially producing new halometabolites, which might be easily missed by traditional isolation and chemical characterization. In addition, our study indicates that great genetic potential of new halometabolites can be expected from mostly untapped actinomycetes from the polar regions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0662-2) contains supplementary material, which is available to authorized users.

Catalytic promiscuity of glycopeptide N-methyltransferases enables bio-orthogonal labelling of biosynthetic intermediates

Remarkable promiscuity of N-methyltransferases enables modulation of biological activity as well as bio-orthogonal labelling of glycopeptide antibiotics and biosynthetic intermediates.

Endless Resistance. Endless Antibiotics?

The practice of medicine was profoundly transformed by the introduction of the antibiotics (compounds isolated from Nature) and the antibacterials (compounds prepared by synthesis) for the control of bacterial infection. As a result of the extraordinary success of these compounds over decades of time, a timeless biological activity for these compounds has been presumed. This presumption is no longer. The inexorable acquisition of resistance mechanisms by bacteria is retransforming medical practice. Credible answers to this dilemma are far better recognized than they are being implemented. In this perspective we examine (and in key respects, reiterate) the chemical and biological strategies being used to address the challenge of bacterial resistance.

The multihued palette of dye-decolorizing peroxidases

Dye-decolorizing peroxidases (DyPs; EC 1.11.1.19) are heme enzymes that comprise a family of the dimeric α+β barrel structural superfamily of proteins. The first DyP, identified relatively recently in the fungus Bjerkandera adusta, was characterized for its ability to catalyze the decolorization of anthraquinone-based industrial dyes. These enzymes are now known to be present in all three domains of life, but do not appear to occur in plants or animals. They are involved in a range of physiological processes, although in many cases their roles remain unknown. This has not prevented the development of their biocatalytic potential, which includes the transformation of lignin. This review highlights the functional diversity of DyPs in the light of phylogenetic, structural and biochemical data. The phylogenetic analysis reveals the existence of at least five classes of DyPs. Their potential physiological roles are discussed based in part on synteny analyses. Finally, the considerable biotechnological potential of DyPs is summarized.

Structural aspects of phenylglycines, their biosynthesis and occurrence in peptide natural products

Phenylglycine-type amino acids occur in a wide variety of peptide natural products. Herein structures and properties of these peptides as well as the biosynthetic origin and incorporation of phenylglycines are discussed.

Glycosyltransferases: mechanisms and applications in natural product development

Glycosylation reactions mainly catalyzed by glycosyltransferases (Gts) occur almost everywhere in the biosphere, and always play crucial roles in vital processes.