Divergent Tandem Acyl Carrier Proteins Necessitate In-Series Polyketide Processing in the Leinamycin Family.

The leinamycin family of polyketides are promising antitumor antibiotics, yet several aspects of their biosynthesis remain elusive. All leinamycin family members bear a sulfur-containing moiety which is essential for the anticancer activity exhibited by leinamycin. The key building blocks required for the incorporation of these functionalities are introduced in the final module of the polyketide synthase (PKS), which elegantly combines β-branching and thiocysteine incorporation to generate a diverse library of sulfur-based molecular scaffolds.

Antibiotic origami: selective formation of spirotetronates in abyssomicin biosynthesis.

The abyssomicins are a structurally intriguing family of bioactive natural products that include compounds with potent antibacterial, antitumour and antiviral activities. The biosynthesis of the characteristic abyssomicin spirotetronate core occurs an enzyme-catalysed intramolecular Diels-Alder reaction, which proceeds one of two distinct stereochemical pathways to generate products differing in configuration at the C15 spirocentre. Using the purified spirotetronate cyclases AbyU (from abyssomicin C/atrop-abyssomicin C biosynthesis) and AbmU (from abyssomicin 2/neoabyssomicin biosynthesis), in combination with synthetic substrate analogues, here we show that stereoselectivity in the spirotetronate-forming [4 + 2]-cycloaddition is controlled by a combination of factors attributable to both the enzyme and substrate.

An Integrated Module Performs Selective 'Online' Epoxidation in the Biosynthesis of the Antibiotic Mupirocin.

The delineation of the complex biosynthesis of the potent antibiotic mupirocin, which consists of a mixture of pseudomonic acids (PAs) isolated from Pseudomonas fluorescens NCIMB 10586, presents significant challenges, and the timing and mechanisms of several key transformations remain elusive. Particularly intriguing are the steps that process the linear backbone from the initial polyketide assembly phase to generate the first cyclic intermediate PA-B. These include epoxidation as well as incorporation of the tetrahydropyran (THP) ring and fatty acid side chain required for biological activity.

Delineation of the complete reaction cycle of a natural Diels-Alderase.

The Diels-Alder reaction is one of the most effective methods for the synthesis of substituted cyclohexenes. The development of protein catalysts for this reaction remains a major priority, affording new sustainable routes to high value target molecules. Whilst a small number of natural enzymes have been shown capable of catalysing [4 + 2] cycloadditions, there is a need for significant mechanistic understanding of how these prospective Diels-Alderases promote catalysis to underpin their development as biocatalysts for use in synthesis.

Combining total synthesis and genetic engineering to probe dihydropyran formation in ambruticin biosynthesis.

The ambruticins are a family of potent antifungal polyketide derived natural products isolated from the myxobacterium . Their unusual structures include a trisubstituted cyclopropyl group and two oxygen heterocycles, a tetrahydropyran (THP) and dihydropyran (DHP). Herein we report a flexible modular approach for the total synthesis of ambruticins which is used to prepare ambruticins F and S as well as in the first total synthesis of 20,21-dihydroambruticin F.

Structure and Function of the α-Hydroxylation Bimodule of the Mupirocin Polyketide Synthase.

Mupirocin is a clinically important antibiotic produced by a -AT Type I polyketide synthase (PKS) in . The major bioactive metabolite, pseudomonic acid A (PA-A), is assembled on a tetrasubstituted tetrahydropyran (THP) core incorporating a 6-hydroxy group proposed to be introduced by α-hydroxylation of the thioester of the acyl carrier protein (ACP) bound polyketide chain. Herein, we describe an in vitro approach combining purified enzyme components, chemical synthesis, isotopic labelling, mass spectrometry and NMR in conjunction with in vivo studies leading to the first characterisation of the α-hydroxylation bimodule of the mupirocin biosynthetic pathway.

Assessment of Library Services in Pediatric Hospitals in the United States and Canada.

This study reports on a 2022 survey of pediatric hospital librarians in the U.S. and Canada to assess the status of staffing, resources, and services in their libraries.

Structure and Function of the α-Hydroxylation Bimodule of the Mupirocin Polyketide Synthase.

Mupirocin is a clinically important antibiotic produced by a trans-AT Type I polyketide synthase (PKS) in Pseudomonas fluorescens. The major bioactive metabolite, pseudomonic acid A (PA-A), is assembled on a tetrasubstituted tetrahydropyran (THP) core incorporating a 6-hydroxy group proposed to be introduced by α-hydroxylation of the thioester of the acyl carrier protein (ACP) bound polyketide chain. Herein, we describe an in vitro approach combining purified enzyme components, chemical synthesis, isotopic labelling, mass spectrometry and NMR in conjunction with in vivo studies leading to the first characterisation of the α-hydroxylation bimodule of the mupirocin biosynthetic pathway.

Interrogation of an Enzyme Library Reveals the Catalytic Plasticity of Naturally Evolved [4+2] Cyclases.

Stereoselective carbon-carbon bond forming reactions are quintessential transformations in organic synthesis. One example is the Diels-Alder reaction, a [4+2] cycloaddition between a conjugated diene and a dienophile to form cyclohexenes. The development of biocatalysts for this reaction is paramount for unlocking sustainable routes to a plethora of important molecules.

Assessment of Library Services at Top-Performing Pediatric Hospitals in the Southeast United States.

The authors compare and contrast the structure and function of librarians and library services using a convenience sample online survey of pediatric hospitals in the Southeast based on the rankings from the Regional U.S. Best Children's Hospitals and Magnet status.

Correction: Back et al. A New Strain with Antibiotic Activity Isolated from the Microbiome of a Mid-Atlantic Deep-Sea Sponge. 2021, , 105.

After publication of this article [...

Biosynthesis of pleuromutilin congeners using an expression platform.

Pleuromutilin is an antibiotic diterpenoid made by and related fungi, and it is the progenitor of a growing class of semi-synthetic antibiotics used in veterinary and human medicine. To harness the biotechnological potential of this natural product class, a full understanding of its biosynthetic pathway is essential. Previously, a linear pathway for pleuromutilin biosynthesis was established.

The Role of Cytochrome P450 AbyV in the Final Stages of Abyssomicin C Biosynthesis.

Abyssomicin C and its atropisomer are potent inhibitors of bacterial folate metabolism. They possess complex polycyclic structures, and their biosynthesis has been shown to involve several unusual enzymatic transformations. Using a combination of synthesis and in vitro assays we reveal that AbyV, a cytochrome P450 enzyme from the gene cluster, catalyses a key late-stage epoxidation required for the installation of the characteristic ether-bridged core of abyssomicin C.

Programmed Iteration Controls the Assembly of the Nonanoic Acid Side Chain of the Antibiotic Mupirocin.

Mupirocin is a clinically important antibiotic produced by NCIMB 10586 that is assembled by a complex -AT polyketide synthase. The polyketide fragment, monic acid, is esterified by a 9-hydroxynonanoic acid (9HN) side chain which is essential for biological activity. The ester side chain assembly is initialised from a 3-hydroxypropionate (3HP) starter unit attached to the acyl carrier protein (ACP) MacpD, but the fate of this species is unknown.

The Role of Cytochrome P450 AbyV in the Final Stages of Abyssomicin C Biosynthesis.

Abyssomicin C and its atropisomer are potent inhibitors of bacterial folate metabolism. They possess complex polycyclic structures, and their biosynthesis has been shown to involve several unusual enzymatic transformations. Using a combination of synthesis and in vitro assays we reveal that AbyV, a cytochrome P450 enzyme from the aby gene cluster, catalyses a key late-stage epoxidation required for the installation of the characteristic ether-bridged core of abyssomicin C.

Programmed Iteration Controls the Assembly of the Nonanoic Acid Side Chain of the Antibiotic Mupirocin.

Mupirocin is a clinically important antibiotic produced by Pseudomonas fluorescens NCIMB 10586 that is assembled by a complex trans-AT polyketide synthase. The polyketide fragment, monic acid, is esterified by a 9-hydroxynonanoic acid (9HN) side chain which is essential for biological activity. The ester side chain assembly is initialised from a 3-hydroxypropionate (3HP) starter unit attached to the acyl carrier protein (ACP) MacpD, but the fate of this species is unknown.

Maleidride biosynthesis - construction of dimeric anhydrides - more than just heads or tails.

Covering: up to early 2022Maleidrides are a family of polyketide-based dimeric natural products isolated from fungi. Many maleidrides possess significant bioactivities, making them attractive pharmaceutical or agrochemical lead compounds. Their unusual biosynthetic pathways have fascinated scientists for decades, with recent advances in our bioinformatic and enzymatic understanding providing further insights into their construction.

In silico analyses of maleidride biosynthetic gene clusters.

Maleidrides are a family of structurally related fungal natural products, many of which possess diverse, potent bioactivities. Previous identification of several maleidride biosynthetic gene clusters, and subsequent experimental work, has determined the 'core' set of genes required to construct the characteristic medium-sized alicyclic ring with maleic anhydride moieties. Through genome mining, this work has used these core genes to discover ten entirely novel putative maleidride biosynthetic gene clusters, amongst both publicly available genomes, and encoded within the genome of the previously un-sequenced epiheveadride producer Wicklowia aquatica CBS 125634.

Cladobotric Acids: Metabolites from Cultures of sp., Semisynthetic Analogues and Antibacterial Activity.

Three new polyketide-derived natural products, cladobotric acids G-I (-), and six known metabolites (, , -) were isolated from fermentation of the fungus sp. grown on rice. Their structures were elucidated by extensive spectroscopic methods.

Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans.

Tetrahydropyrans (THPs) are common structural motifs found in natural products and synthetic therapeutic molecules. In Nature these 6-membered oxygen heterocycles are often assembled intramolecular reactions involving either oxy-Michael additions or ring opening of epoxy-alcohols. Indeed, the polyether natural products have been particularly widely studied due to their fascinating structures and important biological properties; these are commonly formed -selective epoxide-opening cascades.

Synthesis and pharmacological characterisation of arctigenin analogues as antagonists of AMPA and kainate receptors.

(-)-Arctigenin and a series of new analogues have been synthesised and then tested for their potential as AMPA and kainate receptor antagonists of human homomeric GluA1 and GluK2 receptors expressed in HEK293 cells using a Ca influx assay. In general, these compounds showed antagonist activity at both receptors with greater activity evident at AMPARs. Schild analysis indicates that a spirocyclic analogue 6c acts as a non-competitive antagonist.

Core Steps to the Azaphilone Family of Fungal Natural Products.

Azaphilones are a family of polyketide-based fungal natural products that exhibit interesting and useful bioactivities. This minireview explores the literature on various characterised azaphilone biosynthetic pathways, which allows for a proposed consensus scheme for the production of the core azaphilone structure, as well as identifying early diversification steps during azaphilone biosynthesis. A consensus understanding of the core enzymatic steps towards a particular family of fungal natural products can aid in genome-mining experiments.

Ambruticins: tetrahydropyran ring formation and total synthesis.

The ambruticins are a family of polyketide natural products which exhibit potent antifungal activity. Gene knockout experiments are in accord with the proposal that the tetrahydropyran ring of the ambruticins is formed via the AmbJ catalysed epoxidation of the unsaturated 3,5-dihydroxy acid, ambruticin J, followed by regioselective cyclisation to ambruticin F. Herein, a convergent approach to the total synthesis of ambruticin J is described as well as model studies involving epoxidation and cyclisations of unsaturated hydroxy esters to give tetrahydropyrans and tetrahydrofurans.

Mixing and matching genes of marine and terrestrial origin in the biosynthesis of the mupirocin antibiotics.

With growing understanding of the underlying pathways of polyketide biosynthesis, along with the continual expansion of the synthetic biology toolkit, it is becoming possible to rationally engineer and fine-tune the polyketide biosynthetic machinery for production of new compounds with improved properties such as stability and/or bioactivity. However, engineering the pathway to the thiomarinol antibiotics has proved challenging. Here we report that genes from a marine sp.

Uncovering biosynthetic relationships between antifungal nonadrides and octadrides.

Maleidrides are a class of bioactive secondary metabolites unique to filamentous fungi, which contain one or more maleic anhydrides fused to a 7-, 8- or 9- membered carbocycle (named heptadrides, octadrides and nonadrides respectively). Herein structural and biosynthetic studies on the antifungal octadride, zopfiellin, and nonadrides scytalidin, deoxyscytalidin and castaneiolide are described. A combination of genome sequencing, bioinformatic analyses, gene disruptions, biotransformations, isotopic feeding studies, NMR and X-ray crystallography revealed that they share a common biosynthetic pathway, diverging only after the nonadride deoxyscytalidin.