Biosynthetic pathway for furanosteroid demethoxyviridin and identification of an unusual pregnane side-chain cleavage

Biosynthesis of fungal terpenoids

Covering: up to August 2023Terpenoids, which are widely distributed in animals, plants, and microorganisms, are a large group of natural products with diverse structures and various biological activities. They have made great contributions to human health as therapeutic agents, such as the anti-cancer drug paclitaxel and anti-malarial agent artemisinin. Accordingly, the biosynthesis of this important class of natural products has been extensively studied, which generally involves two major steps: hydrocarbon skeleton construction by terpenoid cyclases and skeleton modification by tailoring enzymes. Additionally, fungi (Ascomycota and Basidiomycota) serve as an important source for the discovery of terpenoids. With the rapid development of sequencing technology and bioinformatics approaches, genome mining has emerged as one of the most effective strategies to discover novel terpenoids from fungi. To date, numerous terpenoid cyclases, including typical class I and class II terpenoid cyclases as well as emerging UbiA-type terpenoid cyclases, have been identified, together with a variety of tailoring enzymes, including cytochrome P450 enzymes, flavin-dependent monooxygenases, and acyltransferases. In this review, our aim is to comprehensively present all fungal terpenoid cyclases identified up to August 2023, with a focus on newly discovered terpenoid cyclases, especially the emerging UbiA-type terpenoid cyclases, and their related tailoring enzymes from 2015 to August 2023.

Biosynthesis of Enfumafungin-type Antibiotic Reveals an Unusual Enzymatic Fusion Pattern and Unprecedented C-C Bond Cleavage

Enfumafungin-type antibiotics, represented by enfumafungin and fuscoatroside, belong to a distinct group of triterpenoids derived from fungi. These compounds exhibit significant antifungal properties with ibrexafungerp, a semisynthetic derivative of enfumafungin, recently gaining FDA's approval as the first oral antifungal drug for treating invasive vulvar candidiasis. Enfumafungin-type antibiotics possess a cleaved E-ring with an oxidized carboxyl group and a reduced methyl group at the break site, suggesting unprecedented C-C bond cleavage chemistry involved in their biosynthesis. Here, we show that a 4-gene (fsoA, fsoD, fsoE, fsoF) biosynthetic gene cluster is sufficient to yield fuscoatroside by heterologous expression in Aspergillus oryzae. Notably, FsoA is an unheard-of terpene cyclase-glycosyltransferase fusion enzyme, affording a triterpene glycoside product that relies on enzymatic fusion. FsoE is a P450 enzyme that catalyzes successive oxidation reactions at C19 to facilitate a C-C bond cleavage, producing an oxidized carboxyl group and a reduced methyl group that have never been observed in known P450 enzymes. Our study thus sets the important foundation for the manufacture of enfumafungin-type antibiotics using biosynthetic approaches.

Recent developments in the enzymatic modifications of steroid scaffolds

Steroids are an important family of bioactive compounds. Steroid drugs are renowned for their multifaceted pharmacological activities and are the second-largest category in the global pharmaceutical market. Recent developments in biocatalysis and biosynthesis have led to the increased use of enzymes to enhance the selectivity, efficiency, and sustainability for diverse modifications of steroids. This review discusses the advancements achieved over the past five years in the enzymatic modifications of steroid scaffolds, focusing on enzymatic hydroxylation, reduction, dehydrogenation, cascade reactions, and other modifications for future research on the synthesis of novel steroid compounds and related drugs, and new therapeutic possibilities.

A new tetracyclic triterpenoid from endophytic fungus Fusarium sporotrichioides

Objective

To isolate bioactive compounds from the endophytic fungus Fusarium sporotrichioides isolated from Rauwolfia yunnanensis, and investigate their pharmacological activities.

Methods

The chemical constituents were isolated and purified by combining with ODS column chromatography, silica gel column chromatography and by performing semipreparative HPLC. Their structures were established on the basis of 1D NMR (1H-NMR and 13C-NMR) and 2D NMR (1H-1H COSY, HSQC, HMBC and NOESY), as well as HRESIMS and comparison with literature data. In addition, the absolute configuration of compound 1 was determined by calculated ECD data.

Results

One previously undescribed tetracyclic triterpenoid derivative, named as integracide L (1), 12α-acetoxy-4,4-dimethyl-24-methylene-5α-cholesta-8,14-diene-2α,3β,11β-triol (2), 12α-acetoxy-4,4-dimethyl-24-methylene-5α-cholesta-8-momoene-2α,3β,11β-triol (3), 12α-acetoxy-4,4-dimethyl-24-methylene-5α-cholesta-8,14-diene-3β,11β-triol (4), and 12α-acetoxy-4,4-dimethyl-24-methylene-5α-cholesta-8-momoene-3β,11β-triol (5) were isolated from F. sporotrichioide. Moreover, compound 1 was rare tetracyclic triterpenoid with single methyl replacement at C-4 position.

Conclusion

Compound 1 was a new tetracyclic triterpenoid isolated from the endophytic fungus F. sporotrichioides. In addition, compound 2 could inhibit the growth of three different human cancer cells significantly. Compounds 3 and 5 were found to possess better cytotoxic activities on HepG-2 cells than the other compounds, with IC50 values of (2.8 ± 0.1) and (6.3 ± 0.3) μmol/L respectively.

The expanded CRISPR toolbox for constructing microbial cell factories

Microbial cell factories (MCFs) convert low-cost carbon sources into valuable compounds. The CRISPR/Cas9 system has revolutionized MCF construction as a remarkable genome editing tool with unprecedented programmability. Recently, the CRISPR toolbox has been significantly expanded through the exploration of new CRISPR systems, the engineering of Cas effectors, and the incorporation of other effectors, enabling multi-level regulation and gene editing free of double-strand breaks. This expanded CRISPR toolbox powerfully promotes MCF construction by facilitating pathway construction, enzyme engineering, flux redistribution, and metabolic burden control. In this article, we summarize different CRISPR tool designs and their applications in MCF construction for gene editing, transcriptional regulation, and enzyme modulation. Finally, we also discuss future perspectives for the development and application of the CRISPR toolbox.

Identification of new bisabosqual-type meroterpenoids reveals non-enzymatic conversion of bisabosquals into seco-bisabosquals

Bisabosqual-type meroterpenoids are fungi-derived polyketide-terpenoid hybrids bearing a 2,3,3a,3a1,9,9a-hexahydro-1H-benzofuro[4,3,2-cde]chromene skeleton (6/6/6/5 ring system) or its seco-C-ring structure, and exhibit diverse bioactivities. Their unique structural architecture and impressive biological activities have led to considerable interest in discovering new analogues. However, to date, only nine analogues have been identified. Herein, we reported the isolation and identification of six new bisabosqual-type meroterpenoids stachybisbins C-H (1-6), together with one known compound bisabosqual C (7), from Stachybotrys bisbyi PYH05-7. Intriguingly, we found that 7, which contains the intact tetracyclic skeleton, can be non-enzymatically converted into its seco derivative stachybisbin I (8), unveiling the biosynthetic relationship between bisabosquals and seco-bisabosquals. Moreover, based on CRISPR/Cas9-mediated gene disruption, we revealed that the three-gene cluster responsible for the formation of LL-Z1272β is associated with the biosynthesis of bisabosqual-type meroterpenoids, and then proposed a plausible route to 1-8.

Characterization of a new fusicoccane-type diterpene synthase and an associated P450 enzyme

Fusicoccane-type terpenoids are a subgroup of diterpenoids featured with a unique 5-8-5 ring system. They are widely distributed in nature and possess a variety of biological activities. Up to date, only five fusicoccane-type diterpene synthases have been identified. Here, we identify a two-gene biosynthetic gene cluster containing a new fusicoccane-type diterpene synthase gene tadA and an associated cytochrome P450 gene tadB from Talaromyces wortmannii ATCC 26942. Heterologous expression reveals that TadA catalyzes the formation of a new fusicoccane-type diterpene talaro-7,13-diene. D2O isotope labeling combined with site-directed mutagenesis indicates that TadA might employ a different C2,6 cyclization strategy from the known fusicoccane-type diterpene synthases, in which a neutral intermediate is firstly formed and then protonated by an environmental proton. In addition, we demonstrate that the associated cytochrome P450 enzyme TadB is able to catalyze multiple oxidation of talaro-7,13-diene to yield talaro-6,13-dien-5,8-dione.

New Report: Genome Mining Untaps the Antibiotics Biosynthetic Gene Cluster of Pseudoalteromonas xiamenensis STKMTI.2 from a Mangrove Soil Sediment

The marine bacterium Pseudoalteromonas xiamenensis STKMTI.2 was isolated from a mangrove soil sediment on Setokok Island, Batam, Indonesia. The genome of this bacterium consisted of 4,563,326 bp (GC content: 43.2%) with 1 chromosome, 2 circular plasmids, 2 linear plasmids, 4,824 protein-coding sequences, 25 rRNAs, 104 tRNAs, 4 ncRNAs, and 1 clustered, regularly interspaced, short palindromic repeated (CRISPR). This strain possessed cluster genes which are responsible for the production of brominated marine pyrroles/phenols (bmp), namely, bmp8 and bmp9. Other gene clusters responsible for the synthesis of secondary metabolites were identified using antiSMASH and BAGEL4, which yielded five results, namely, non-ribosomal peptides, polyketide-like butyrolactone, Lant class I, and RiPP-like, detected in chromosome 1, while prodigiosin was detected in the unnamed plasmid 5. This suggests that these whole genome data will be of remarkable importance for the improved understanding of the biosynthesis of industrially important bioactive and antibacterial compounds produced by P. xiamenensis STKMTI.2.

Biosynthetic Studies of Phomopsins Unveil Posttranslational Installation of Dehydroamino Acids by UstYa Family Proteins

UstYa family proteins (DUF3328) are widely and specifically distributed in fungi. They are known to be involved in the biosynthesis of ribosomally synthesized and posttranslationally modified peptides (RiPPs) and nonribosomal peptides, and possibly catalyze various reactions, including oxidative cyclization and chlorination. In this study, we focused on phomopsin A, a fungal RiPP consisting of unique nonproteinogenic amino acids. Gene knockout experiments demonstrated that three UstYa homologues, phomYc, phomYd, and phomYe, are essential for the desaturation of amino acid moieties, showing unprecedented function among UstYa family proteins. Sequence similarity network analysis indicated that their amino acid sequences are highly diverged and that most remain uncharacterized, paving the way for genome mining of fungal metabolites with unique modifications.

Genome mining methods to discover bioactive natural products

Covering: 2016 to 2021With genetic information available for hundreds of thousands of organisms in publicly accessible databases, scientists have an unprecedented opportunity to meticulously survey the diversity and inner workings of life. The natural product research community has harnessed this breadth of sequence information to mine microbes, plants, and animals for biosynthetic enzymes capable of producing bioactive compounds. Several orthogonal genome mining strategies have been developed in recent years to target specific chemical features or biological properties of bioactive molecules using biosynthetic, resistance, or transporter proteins. These "biosynthetic hooks" allow researchers to query for biosynthetic gene clusters with a high probability of encoding previously undiscovered, bioactive compounds. This review highlights recent case studies that feature orthogonal approaches that exploit genomic information to specifically discover bioactive natural products and their gene clusters.

Comparative analyses of the Hymenoscyphus fraxineus and Hymenoscyphus albidus genomes reveals potentially adaptive differences in secondary metabolite and transposable element repertoires

Background

The dieback epidemic decimating common ash (Fraxinus excelsior) in Europe is caused by the invasive fungus Hymenoscyphus fraxineus. In this study we analyzed the genomes of H. fraxineus and H. albidus, its native but, now essentially displaced, non-pathogenic sister species, and compared them with several other members of Helotiales. The focus of the analyses was to identify signals in the genome that may explain the rapid establishment of H. fraxineus and displacement of H. albidus.

Results

The genomes of H. fraxineus and H. albidus showed a high level of synteny and identity. The assembly of H. fraxineus is 13 Mb longer than that of H. albidus’, most of this difference can be attributed to higher dispersed repeat content (i.e. transposable elements [TEs]) in H. fraxineus. In general, TE families in H. fraxineus showed more signals of repeat-induced point mutations (RIP) than in H. albidus, especially in Long-terminal repeat (LTR)/Copia and LTR/Gypsy elements.

Comparing gene family expansions and 1:1 orthologs, relatively few genes show signs of positive selection between species. However, several of those did appeared to be associated with secondary metabolite genes families, including gene families containing two of the genes in the H. fraxineus-specific, hymenosetin biosynthetic gene cluster (BGC).

Conclusion

The genomes of H. fraxineus and H. albidus show a high degree of synteny, and are rich in both TEs and BGCs, but the genomic signatures also indicated that H. albidus may be less well equipped to adapt and maintain its ecological niche in a rapidly changing environment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07837-2.

Secondary metabolite biosynthetic diversity in the fungal family Hypoxylaceae and Xylaria hypoxylon

To date little is known about the genetic background that drives the production and diversification of secondary metabolites in the Hypoxylaceae. With the recent availability of high-quality genome sequences for 13 representative species and one relative (Xylaria hypoxylon) we attempted to survey the diversity of biosynthetic pathways in these organisms to investigate their true potential as secondary metabolite producers. Manual search strategies based on the accumulated knowledge on biosynthesis in fungi enabled us to identify 783 biosynthetic pathways across 14 studied species, the majority of which were arranged in biosynthetic gene clusters (BGC). The similarity of BGCs was analysed with the BiG-SCAPE engine which organised the BGCs into 375 gene cluster families (GCF). Only ten GCFs were conserved across all of these fungi indicating that speciation is accompanied by changes in secondary metabolism. From the known compounds produced by the family members some can be directly correlated with identified BGCs which is highlighted herein by the azaphilone, dihydroxynaphthalene, tropolone, cytochalasan, terrequinone, terphenyl and brasilane pathways giving insights into the evolution and diversification of those compound classes. Vice versa, products of various BGCs can be predicted through homology analysis with known pathways from other fungi as shown for the identified ergot alkaloid, trigazaphilone, curvupallide, viridicatumtoxin and swainsonine BGCs. However, the majority of BGCs had no obvious links to known products from the Hypoxylaceae or other well-studied biosynthetic pathways from fungi. These findings highlight that the number of known compounds strongly underrepresents the biosynthetic potential in these fungi and that a tremendous number of unidentified secondary metabolites is still hidden. Moreover, with increasing numbers of genomes for further Hypoxylaceae species becoming available, the likelihood of revealing new biosynthetic pathways that encode new, potentially useful compounds will significantly improve. Reaching a better understanding of the biology of these producers, and further development of genetic methods for their manipulation, will be crucial to access their treasures.

Recent progress in the synthesis of the furanosteroid family of natural products

This review focuses on an overview of recent advances in the synthesis of furanosteroids and illustrates their applications in medicinal chemistry over the period of 2005–present.

Cytochrome P450 enzymes in fungal natural product biosynthesis

Covering: 2015 to the end of 2020 Fungal-derived polyketides, non-ribosomal peptides, terpenoids and their hybrids contribute significantly to the chemical space of total natural products. Cytochrome P450 enzymes play essential roles in fungal natural product biosynthesis with their broad substrate scope, great catalytic versatility and high frequency of involvement. Due to the membrane-bound nature, the functional and mechanistic understandings for fungal P450s have been limited for quite a long time. However, recent technical advances, such as the efficient and precise genome editing techniques and the development of several filamentous fungal strains as heterologous P450 expression hosts, have led to remarkable achievements in fungal P450 studies. Here, we provide a comprehensive review to cover the most recent progresses from 2015 to 2020 on catalytic functions and mechanisms, research methodologies and remaining challenges in the fast-growing field of fungal natural product biosynthetic P450s.

Anticancer fungal natural products: Mechanisms of action and biosynthesis

Many fungal metabolites show promising anticancer properties both in vitro and in animal models, and some synthetic analogs of those metabolites have progressed into clinical trials. However, currently, there are still no fungi-derived agents approved as anticancer drugs. Two potential reasons could be envisioned: 1) lacking a clear understanding of their anticancer mechanism of action, 2) unable to supply enough materials to support the preclinical and clinic developments. In this review, we will summarize recent efforts on elucidating the anticancer mechanisms and biosynthetic pathways of several promising anticancer fungal natural products.

Recent advances in dissecting the demethylation reactions in natural product biosynthesis

Demethylation is a chemical process widely distributed in nature to remove a methyl group from an organic molecule, which is a key aspect of diverse biological processes including biosynthesis of natural products, degradation of plant biomass and epigenetic regulation. This process is facilitated by diverse demethylases via distinct mechanisms. Recent studies have disclosed some novel demethylation reactions as well as their underlying demethylases in the biosynthesis of bacterial sterols, fungal terpenoids, and plant alkaloids. This article focuses on current advances in dissecting the demethylation reactions in biosynthesis of natural products and aims to point out the enzymatic mechanisms, which will further enhance our knowledge and understanding of demethylation process in nature.

Reconstitution of biosynthetic machinery of fungal natural products in heterologous hosts

Ascomycota and basidiomycota fungi are prolific sources of biologically active natural products. Recent genomic data and bioinformatic analysis indicate that fungi possess a large number of biosynthetic gene clusters for bioactive natural products but more than 90% are silent. Heterologous expression in the filamentous fungi as hosts is one of the powerful tools to expression of the silent gene clusters. This review introduces recent studies on the total biosynthesis of representative family members via common platform intermediates, genome mining of novel di- and sesterterpenoids including detailed cyclization pathway, and development of expression host for basidiomycota genes with efficient genome editing method. In addition, this review will discuss the several strategies, for the generation of structural diversity, which are found through these studies.

Biosynthetic Study of Cephalosporin P1 Reveals a Multifunctional P450 Enzyme and a Site-Selective Acetyltransferase

Fusidane-type antibiotics are a group of triterpenoid antibiotics. They include helvolic acid, fusidic acid, and cephalosporin P₁, among which fusidic acid has been used clinically. We have recently elucidated the biosynthesis of helvolic acid and fusidic acid, which share an early biosynthetic route involving six conserved enzymes. Here, we report two separate gene clusters for cephalosporin P₁ biosynthesis. One consists of the six conserved genes, and the other contains three genes encoding a P450 enzyme (CepB4), an acetyltransferase (CepD2), and a short-chain dehydrogenase/reductase (CepC2). Introduction of these three genes into Aspergillus oryzae, which harbors the six conserved genes, produced cephalosporin P₁. Stepwise introduction revealed that CepB4 not only catalyzes stereoselective dual oxidation of C6 and C7, but also monooxygenation of C6 or C7. This led to the generation of five new analogues. Using monohydroxylated products as substrates, we demonstrated that CepD2 specifically acetylates C6-OH, although both C6-OH and C7-OH acetylated analogues have been identified in nature.

Sporormielones A–E, bioactive novel C–C coupled orsellinic acid derivative dimers, and their biosynthetic origin

Sporormielones A–E, novel C–C coupled orsellinic acid derivative dimers containing tricyclic cores with a dimethylcyclopentenone unit, were isolated from Sporormiella sp., and their plausible biosynthetic mechanism was proposed.

Study of the Binding Interaction between Wortmannin and Calf Thymus DNA: Multispectroscopic and Molecular Docking Studies

INTRODUCTION

Wortmannin (WTN) is a steroid metabolite that inhibits phosphatidylinositol 3-kinase and other signaling pathways. Structurally, the WTN consists of a cyclopentanophenanthrene-like structure with several oxygen-rich moieties which have the potential to interact with deoxyribonucleic acid (DNA) molecules.

METHODS

We aim to evaluate the WTN and calf thymus DNA (ct-DNA) interaction with molecular docking using the AutoDock 4.2 software. UV and fluorescence spectroscopy and viscosity techniques were performed to confirm the in silico analysis.

RESULTS

Molecular docking showed that the WTN interacted with ct-DNA via hydrogen bonds at guanine-rich sequences. The number of hydrogen bonds between the WTN and DNA was 1-2 bonds (average 1.2) per WTN molecule. The in silico binding constant was 2 × 103 M-1. UV spectroscopy showed that the WTN induced a hyperchromic feature without wavelength shifting. The WTN and DNA interaction led to quenching of DNA-emitted fluorescence. The different concentrations of WTN had no effect on DNA viscosity. Taken together, our results demonstrated WTN interacts with DNA in the nonintercalating mode, which is considered as a new mechanism of action.

CONCLUSION

These results suggest that the WTN may exert its biological effects, at least in part, via interaction with DNA.

Hyfraxinic Acid, a Phytotoxic Tetrasubstituted Octanoic Acid, Produced by the Ash (Fraxinus excelsior L.) Pathogen Hymenoscyphus fraxineus Together with Viridiol and Some of Its Analogues

A new tetrasubstituted octanoic acid, named hyfraxinic acid (1), was isolated together with known 1-deoxyviridiol (2), viridiol (3), nodulisporiviridin M (4), and demethoxyviridiol (5) from the organic extract of Hymenoscyphus fraxineus responsible for ash (Fraxinus excelsior L.) dieback in Europe. Hyfraxinic acid (1) was characterized, using spectroscopic methods, as 2,4-dihydroxy-7-methyl-6-methyleneoctanoic acid. Furthermore, the advanced Mosher method was used to determine the absolute configuration (3R) of 1-deoxyviridiol. Nodulisporiviridin M (4) was isolated for the first time from H. fraxineus. The phytotoxicity of each compound was tested by a leaf puncture assay on Celtis australis L., Quercus suber L., Hedera elix L., Juglans regia L., and Fraxinus angustifolia L. leaves. Compounds 1, 3, and 5 exhibited remarkable phytotoxicity on all plants tested, inducing necrotic lesions at concentrations of 1.0 and 0.5 mg/mL, while compounds 2 and 4 were found to be inactive in this bioassay. These results could contribute to a deeper understanding of the pathogenicity of H. fraxineus.

Observations on Texas hypoxylons, including two new Hypoxylon species and widespread environmental isolates of the H. croceum complex identified by a polyphasic approach

Two new species and a new combination of Hypoxylon from Texas were identified and described based on morphological, multigene phylogenetic (ITS [nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2], 28S [5' 1200 bp of nuc 28S rDNA], RPB2 [partial second largest subunit of the DNA-directed RNA polymerase II], TUB2 [partial β-tubulin]), and chemotaxonomic data. Hypoxylon olivaceopigmentum is characterized by its pulvinate to glomerate stromata, olivaceous KOH-extractable pigments, equilateral ascospores, and indehiscent perispore. Hypoxylon texense can be distinguished from morphologically similar species by its rust to dark brick KOH-extractable pigments and the high-performance liquid chromatography (HPLC) profile of its stromatal secondary metabolites. Hypoxylon hinnuleum is proposed as the sexual morph of Nodulisporium hinnuleum, featuring dark vinaceous glomerate stromata with dark brick KOH-extractable pigments composed of cohaerin-type azaphilones and smooth equilateral ascospores with indehiscent perispore. Based on these diagnostic characters, H. hinnuleum forms a complex with H. croceum and H. minicroceum. More than 50 ITS sequences with high identity originating from North American and East Asian environmental isolates formed a well-supported clade with the type of N. hinnuleum, demonstrating the widespread distribution of the species complex. In addition, updated descriptions and comprehensive illustrations with detailed information on the diagnostic features of H. fendleri and H. perforatum are provided. The multilocus phylogenetic reconstruction of Hypoxylon supported the status of the new species and broadened the knowledge about intergeneric relationships.

Wortmannin and Wortmannine Analogues from an Undescribed Niesslia sp

In the course of our studies of coprophilous fungi as sources of antifungal agents, a strain of an undescribed species in the genus Niesslia (TTI-0426) was isolated from horse dung collected in Texas. An extract from fermentation cultures of this strain afforded two new antifungal wortmannin derivatives, wortmannins C and D (1 and 2), as well as four additional new related compounds, wortmannines B1-B4 (3-6), containing an unusual ring system. The structures of these metabolites were established mainly by analysis of HRESIMS and 2D NMR data. Relative configurations were assigned using NOESY data, and the structure assignments were supported by NMR comparison with similar compounds. Wortmannins C and D showed activity against Cryptococcus neoformans and Candida albicans in disk assays, but low MIC potency observed for 1 was suggested to be due in part to efflux processes on the basis of assay results for a Schizosaccharomyces pombe efflux mutant in comparison to wild-type.

Biosynthesis of clinically used antibiotic fusidic acid and identification of two short-chain dehydrogenase/reductases with converse stereoselectivity

Fusidic acid is the only fusidane-type antibiotic that has been clinically used. However, biosynthesis of this important molecule in fungi is poorly understood. We have recently elucidated the biosynthesis of fusidane-type antibiotic helvolic acid, which provides us with clues to identify a possible gene cluster for fusidic acid (fus cluster). This gene cluster consists of eight genes, among which six are conserved in the helvolic acid gene cluster except fusC1 and fusB1. Introduction of the two genes into the Aspergillus oryzae NSAR1 expressing the conserved six genes led to the production of fusidic acid. A stepwise introduction of fusC1 and fusB1 revealed that the two genes worked independently without a strict reaction order. Notably, we identified two short-chain dehydrogenase/reductase genes fusC1 and fusC2 in the fus cluster, which showed converse stereoselectivity in 3-ketoreduction. This is the first report on the biosynthesis and heterologous expression of fusidic acid.

Biosynthesis of an anti-tuberculosis sesterterpenoid asperterpenoid A

Biosynthesis of a potent MptpB inhibitor asperterpenoid A by a sesterterpene cyclase AstC and a multifunctional P450 enzyme AstB.

Native roles of Baeyer–Villiger monooxygenases in the microbial metabolism of natural compounds

Baeyer–Villiger monooxygenases function in the primary metabolism of atypical carbon sources, as well as the synthesis of complex microbial metabolites.