Non-Heme Iron Enzymes Catalyze Heterobicyclic and Spirocyclic Isoquinolone Core Formation in Piperazine Alkaloid Biosynthesis.

We report the discovery and biosynthesis of new piperazine alkaloids-arizonamides, and their derived compounds-arizolidines, featuring heterobicyclic and spirocyclic isoquinolone skeletons, respectively. Their biosynthetic pathway involves two crucial non-heme iron enzymes, ParF and ParG, for core skeleton construction. ParF has a dual function facilitating 2,3-alkene formation of helvamide, as a substrate for ParG, and oxidative cleavage of piperazine. Notably, ParG exhibits catalytic versatility in multiple oxidative reactions, including cyclization and ring reconstruction. A key amino acid residue Phe67 was characterized to control the formation of the constrained arizonamide B backbone by ParG.

Characterization and catalytic investigation of fungal single-module nonribosomal peptide synthetase in terpene-amino acid meroterpenoid biosynthesis.

Hybrid natural products are compounds that originate from diverse biosynthetic pathways and undergo a conjugation process, which enables them to expand their chemical diversity and biological functionality. Terpene-amino acid meroterpenoids have garnered increasing attention in recent years, driven by the discovery of noteworthy examples such as the anthelmintic CJ-12662, the insecticidal paeciloxazine, and aculene A (1). In the biosynthesis of terpene-amino acid natural products, single-module nonribosomal peptide synthetases (NRPSs) have been identified to be involved in the esterification step, catalyzing the fusion of modified terpene and amino acid components. Despite prior investigations into these NRPSs through gene deletion or in vivo experiments, the enzymatic basis and mechanistic insights underlying this family of single-module NRPSs remain unclear. In this study, we performed biochemical characterization of AneB by in vitro characterization, molecular docking, and site-directed mutagenesis. The enzyme reaction analyses, performed with L-proline and daucane/nordaucane sesquiterpene substrates, revealed that AneB specifically esterifies the C10-OH of aculenes with L-proline. Notably, in contrast to ThmA in CJ-12662 biosynthesis, which exclusively recognizes oxygenated amorpha-4,11-diene sesquiterpenes for L-tryptophan transfer, AneB demonstrates broad substrate selectivity, including oxygenated amorpha-4,11-diene and 2-phenylethanol, resulting in the production of diverse unnatural prolyl compounds. Furthermore, site-directed mutagenesis experiments indicated the involvement of H794 and D798 in the esterification catalyzed by AneB. Lastly, domain swapping between AneB and ThmA unveiled that the A‒T domains of ThmA can be effectively harnessed by the C domain of AneB for L-tryptophan transfer, thus highlighting the potential of the C domain of AneB for generating various terpene-amino acid meroterpenoid derivatives. ONE-SENTENCE SUMMARY: The enzymatic basis and mechanistic insights into AneB, a single-module NRPS, highlight its capacity to generate various terpene-amino acid meroterpenoid derivatives.

Synthesis, evaluation, and mechanism of 1-(4-(arylethylenylcarbonyl)phenyl)-4-carboxy-2-pyrrolidinones as potent reversible SARS-CoV-2 entry inhibitors.

A class of 1-(4-(arylethylenylcarbonyl)phenyl)-4-carboxy-2-pyrrolidinones were designed and synthesized via Michael addition, cyclization, aldol condensation, and deprotonation to inhibit the human transmembrane protease serine 2 (TMPRSS2) and Furin, which are involved in priming the SARS-CoV-2 Spike for virus entry. The most potent inhibitor 2f (81) was found to efficiently inhibit the replication of various SARS-CoV-2 delta and omicron variants in VeroE6 and Calu-3 cells, with EC50 range of 0.001-0.026 µM by pre-incubation with the virus to avoid the virus entry. The more potent antiviral activities than the proteases inhibitory activities led to discovery that the synthesized compounds also inhibited Spike's receptor binding domain (RBD):angiotensin converting enzyme 2 (ACE2) interaction as a main target, and their antiviral activities were enhanced by inhibiting TMPRSS2 and/or Furin. To further confirm the blocking effect of 2f (81) on virus entry, SARS-CoV-2 Spike pseudovirus was used in the entry assay and the results showed that the compound inhibited the pseudovirus entry in a ACE2-dependent pathway, via mainly inhibiting RBD:ACE2 interaction and TMPRSS2 activity in Calu-3 cells. Finally, in the in vivo animal model of SARS-CoV-2 infection, the oral administration of 25 mg/kg 2f (81) in hamsters resulted in reduced bodyweight loss and 5-fold lower viral RNA levels in nasal turbinate three days post-infection. Our findings demonstrated the potential of the lead compound for further preclinical investigation as a potential treatment for SARS-CoV-2.

Terpene Synthases in the Biosynthesis of Drimane-Type Sesquiterpenes across Diverse Organisms.

Drimane-type sesquiterpenes (DTSs) are significant terpenoid natural products characterized by their unique C15 bicyclic skeleton. They are produced by various organisms including plants, fungi, bacteria and marine organisms, and exhibit a diverse array of bioactivities. These bioactivities encompass antifeedant, anti-insecticidal, anti-bacterial, anti-fungal, anti-viral and anti-proliferative properties. Some DTSs contribute to the pungent flavor found in herb plants like water pepper, while others serve as active components responsible for the anti-cancer activities observed in medicinal mushrooms such as (-)-antrocin from Antrodia cinnamomea. Recently, DTS synthases have been identified in various organisms, biosynthesizing drimenol, drim-8-ene-11-ol and (+)-albicanol, which all possess the characteristic drimane skeleton. Interestingly, despite these enzymes producing chemical molecules with a drimane scaffold, they exhibit minimal amino acid sequence identity across different organisms. This Concept article focuses on the discovery of DTS synthases and the tailoring enzymes generating the chemical diversity of drimane natural products. We summarize and discuss their key features, including the chemical mechanisms, catalytic motifs and functional domains employed by these terpene synthases to generate DTS scaffolds.

Relapsing autoimmune inner ear disease with significant response to methotrexate and azathioprine combination therapy: A case report and mini literature review.

RATIONALE: Autoimmune inner ear disease typically presents with bilateral hearing loss that progresses over weeks or months though its mechanisms are unknown. Corticosteroids are the first-line treatment, but their responses are variable and relapses are frequent. Thus, many experts have sought to replace corticosteroids with immunosuppressive agents. PATIENT CONCERNS: A 35-year-old woman experienced a progressive hearing impairment, initially on the left side and later becoming bilateral. Her response to corticosteroid monotherapy was temporary, and there have been two relapse episodes over several months. DIAGNOSES: Autoimmune inner ear disease was considered due to evidence of autoimmunity combined with a clinical course of bilateral and recurrent sensorineural hearing loss and a partial response to corticosteroid therapy. INTERVENTIONS: The patient received a 3-day mini-pulse of methylprednisolone at 250 mg/d, followed by 12 mg/d maintenance, and concurrently began an azathioprine regimen gradually increasing to 100 mg/day as a corticosteroid-sparing agent. OUTCOMES: Three weeks after immunosuppressive therapy, hearing and pure-tone audiometry improved, and after 7 weeks, methylprednisolone was tapered to 8 mg/d. The dosage was further reduced by adding methotrexate at 7.5 mg/week, resulting in a reduction to 4 mg/d as maintenance therapy after 4 weeks. LESSONS: For patients who are unresponsive to corticosteroids or experience difficulty tolerating them, a combination therapy of methotrexate and azathioprine is recommended as a viable alternative as this regimen is well-tolerated and yields positive outcomes.

Psychometric Properties of the Traditional Chinese Version of the Venous Leg Ulcer Quality of Life Questionnaire.

OBJECTIVE: Symptoms and treatment of venous leg ulcers (VLUs) adversely impact patients' quality of life (QoL). There is no QoL tool that considers the linguistic and cultural specificities of patients with VLU in Taiwan. This study aimed to evaluate the psychometric properties of the traditional Chinese version of the Venous Leg Ulcer Quality of Life Questionnaire (VLU-QoL). METHODS: The processes of translation and cultural adaptation of the VLU-QoL from English to traditional Chinese included forward translation, back translation, linguistic modification, and expert review. Using a sample of 167 patients with VLU from a hospital in southern Taiwan, the psychometric properties analyzed were internal consistency, test-retest reliability, content validity, convergent validity, and criterion-related. RESULTS: The traditional Chinese version of the VLU-QoL demonstrated good overall internal consistency (Cronbach α = .95) and overall test-retest reliability coefficient (r = 0.98). Confirmatory factor analysis was used to assess the convergent validity of the scale; results showed that the Activity, Psychology, and Symptom Distress constructs had acceptable fit and a structure similar to that of the original scale. The scale had its criterion-related validity verified using the Taiwanese version of the 36-item Short-Form Health Survey, demonstrating a good correlation coefficient r that ranged from -0.7 to -0.2 (P < .001). CONCLUSIONS: The Chinese version of the VLU-QoL is valid and reliable for assessing the QoL in patients with VLU, delivering a tool that nurses can use to deliver timely and appropriate care to improve patients' QoL.

Genome mining of cryptic bisabolenes that were biosynthesized by intramembrane terpene synthases from Antrodia cinnamomea.

Terpenoids represent the largest structural family of natural products (NPs) and have various applications in the pharmaceutical, food and fragrance industries. Their diverse scaffolds are generated via a multi-step cyclization cascade of linear isoprene substrates catalysed by terpene synthases (TPSs). Bisabolene NPs, which are sesquiterpenes (C15), have wide applications in medicines and biofuels and serve as bioactive substances in ecology. Despite the discovery of some canonical class I TPSs that synthesize bisabolenes from plants, bacteria and insects, it remained unknown whether any bisabolene synthases from fungi could produce bisabolenes as a main product. Antrodia cinnamomea, a Basidiomycota fungus, is a medicinal mushroom indigenous to Taiwan and a known prolific producer of bioactive terpenoids, but little is known regarding the enzymes involved in the biosynthetic pathways. Here, we applied a genome mining approach against A. cinnamomea and discovered two non-canonical UbiA-type TPSs that both synthesize (+)-(S,Z)-α-bisabolene (1). It was determined that two tailoring enzymes, a P450 monooxygenase and a methyltransferase, install a C14-methyl ester on the bisabolene scaffold. In addition, four new bisabolene derivatives, 2 and 4-6, were characterized from heterologous reconstitution in Saccharomyces cerevisiae. Our study uncovered enzymatic tools to generate structurally diverse bisabolene NPs. This article is part of the theme issue 'Reactivity and mechanism in chemical and synthetic biology'.

The Biosynthetic Gene Cluster of Mushroom-Derived Antrocin Encodes Two Dual-Functional Haloacid Dehalogenase-like Terpene Cyclases.

(-)-Antrocin (1), produced by the medicinal mushroom Antrodia cinnamomea, is a potent antiproliferative compound. The biosynthetic gene cluster of 1 was identified, and the pathway was characterized by heterologous expression. We characterized a haloacid dehalogenase-like terpene cyclase AncC that biosynthesizes the drimane-type sesquiterpene (+)-albicanol (2) from farnesyl pyrophosphate (FPP). Biochemical characterization of AncC, including kinetic studies and mutagenesis, demonstrated the functions of two domains: a terpene cyclase (TC) and a pyrophosphatase (PPase). The TC domain first cyclizes FPP to albicanyl pyrophosphate, and the PPase domain then removes the pyrophosphate to form 2. Intriguingly, AncA (94 % sequence identity to AncC), in the same gene cluster, converts FPP into (R)-trans-γ-monocyclofarnesol instead of 2. Notably, Y283/F375 in the TC domain of AncA serve as a gatekeeper in controlling the formation of a cyclofarnesoid rather than a drimane-type scaffold.

Biosynthesis of Piperazine-Derived Diazabicyclic Alkaloids Involves a Nonribosomal Peptide Synthetase and Subsequent Tailoring by a Multifunctional Cytochrome P450 Enzyme.

Piperazine-derived diazabicycles are privileged structures found in natural products and synthetic chemical entities, including therapeutic agents. Herein, we deciphered the biosynthesis of two unique classes of diazabicyclic alkaloids, fischerazines A-C. Notably, we characterized a multifunctional P450 monooxygenase NfiC that installs ortho-dihydroxyl groups on the dibenzyl-piperazines, in turn triggering a range of NfiC-catalyzed and spontaneous cyclization events.

Potential predictors of quality of life in patients with venous leg ulcers: A cross-sectional study in Taiwan.

Internationally, the impact of venous leg ulcers (VLUs) on the quality of life is well recognised; however, in Taiwan, the focus is only on chronic wound management. This cross-sectional correlational study conducted at the cardiovascular and plastic surgery clinics of a regional teaching hospital between August 2019 and June 2020 investigates venous clinical severity, pain, fatigue, depression, sleep quality, quality of life, and related factors among 167 patients with VLUs. The potential predictors of the quality of life in terms of activities were venous clinical severity (P < 0.001), pain (P = 0.004), and fatigue (P < 0.001) after adjusting for covariates. The potential predictors of the quality of life in terms of the psychological domain were marital status (single/divorced) (P = 0.016), marital status (widowed) (P = 0.027), venous clinical severity (P < 0.001), pain (P = 0.001), and fatigue (P = 0.002). The potential predictors of the quality of life with regard to symptoms were venous clinical severity (P < 0.001), pain (P < 0.001), fatigue (P = 0.001), and depression (P = 0.038). These potential predictors can serve as the basis of interventions for patients with VLUs, such as those related to nutrition or training in wound dressing.

An Enzyme-Mediated Aza-Michael Addition Is Involved in the Biosynthesis of an Imidazoyl Hybrid Product of Conidiogenone B.

Meleagrin B is a terpene-alkaloid hybrid natural product that contains both the conidiogenone and meleagrin scaffold. Their derivatives show diverse biological activities. We characterized the biosynthesis of (-)-conidiogenone B (1), which involves a diterpene synthase and a P450 monooxygenase. In addition, an α,ß-hydrolase (Con-ABH) was shown to catalyze an aza-Michael addition between 1 and imidazole to give 3S-imidazolyl conidiogenone B (6). Compound 6 was more potent than 1 against Staphylococcus aureus strains.

Discovery of a Dual Function Cytochrome†P450 that Catalyzes Enyne Formation in Cyclohexanoid Terpenoid Biosynthesis.

The 1,3-enyne moiety is commonly found in cyclohexanoid natural products produced by endophytic and plant pathogenic fungi. Asperpentyn (1) is a 1,3-enyne-containing cyclohexanoid terpenoid isolated from Aspergillus and Pestalotiopsis. The genetic basis and biochemical mechanism of 1,3-enyne biosynthesis in 1, and other natural products containing this motif, has remained enigmatic despite their potential ecological roles. Identified here is the biosynthetic gene cluster and characterization of two crucial enzymes in the biosynthesis of 1. A P450 monooxygenase that has a dual function, to first catalyze dehydrogenation of the prenyl chain to generate a cis-diene intermediate and then serve as an acetylenase to yield an alkyne moiety, and thus the 1,3-enyne, was discovered. A UbiA prenyltransferase was also characterized and it is unusual in that it favors transferring a five-carbon prenyl chain, rather than a polyprenyl chain, to a p-hydroxybenzoic acid acceptor.

Enzyme-Catalyzed Azepinoindole Formation in Clavine Alkaloid Biosynthesis.

(-)-Aurantioclavine (1), which contains a characteristic seven-membered ring fused to an indole ring, belongs to the azepinoindole class of fungal clavine alkaloids. Here we show that starting from a 4-dimethylallyl-l-tryptophan precursor, a flavin adenine dinucleotide (FAD)-binding oxidase and a catalase-like heme-containing protein are involved in the biosynthesis of 1. The function of these two enzymes was characterized by heterologous expression, in vitro characterization, and deuterium labeling experiments.

Biosynthesis of the fungal glyceraldehyde-3-phosphate dehydrogenase inhibitor heptelidic acid and mechanism of self-resistance.

Overcoming resistance to bioactive small molecules is a significant challenge for health care and agriculture. As a result, efforts to uncover the mechanisms of resistance are essential to the development of new antibiotics, anticancer drugs and pesticides. To study how nature evolves resistance to highly potent natural products, we examined the biosynthesis and mechanism of self-resistance of the fungal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) inhibitor heptelidic acid (HA). HA is a nanomolar inhibitor of GADPH through the covalent modification of the active site cysteine thiol. The biosynthetic pathway of HA was elucidated, which uncovered the enzymatic basis of formation of the epoxide warhead. Structure-activity relationship study using biosynthetic intermediates established the importance of the fused lactone ring system in HA. The molecular basis of HA inhibiting human GAPDH was illustrated through the crystal structure of Hs-GAPDH covalently bound with HA. A GAPDH isozyme HepG encoded in the HA cluster was characterized to be less sensitive to HA, and therefore contribute to self-resistance for the producing host. Comparison of the crystal structures of human GAPDH and HepG showed mutations both within and remote to the active site can contribute to resistance of inactivation, which was confirmed through mutagenesis. Due to the critical role GAPDH plays in aerobic glycolysis and other cellular functions, knowledge of HA mode of action and self-resistance mechanism could accelerate the development of improved inhibitors.

The Biosynthesis of Norsesquiterpene Aculenes Requires Three Cytochrome P450 Enzymes to Catalyze a Stepwise Demethylation Process.

Aculenes are a unique class of norsequiterpenes (C14 ) that are produced by Aspergillus aculeatus. The nordaucane skeleton in aculenes A-D may be derived from an ent-daucane precursor through demethylation, however, the enzymes involved remain unexplored. We identified the biosynthetic gene cluster and characterized the biosynthetic pathway based on gene inactivation, feeding experiments, and heterologous reconstitution in Saccharomyces cerevisiae and Aspergillus oryzae. We discovered that three cytochrome P450 monoxygenases are required to catalyze the stepwise demethylation process. AneF converts the 12-methyl group into a carboxylic acid and AneD installs the 10-hydroxy group for later tautomerization and stabilization. Finally, AneG installs an electron-withdrawing carbonyl group at the C-2 position, which triggers C-12 decarboxylation to yield the nordaucane skeleton. Additionally, a terpene cyclase (AneC) was found that forms a new product (dauca-4,7-diene).

Detecting and prioritizing biosynthetic gene clusters for bioactive compounds in bacteria and fungi.

Secondary metabolites (SM) produced by fungi and bacteria have long been of exceptional interest owing to their unique biomedical ramifications. The traditional discovery of new natural products that was mainly driven by bioactivity screening has now experienced a fresh new approach in the form of genome mining. Several bioinformatics tools have been continuously developed to detect potential biosynthetic gene clusters (BGCs) that are responsible for the production of SM. Although the principles underlying the computation of these tools have been discussed, the biological background is left underrated and ambiguous. In this review, we emphasize the biological hypotheses in BGC formation driven from the observations across genomes in bacteria and fungi, and provide a comprehensive list of updated algorithms/tools exclusively for BGC detection. Our review points to a direction that the biological hypotheses should be systematically incorporated into the BGC prediction and assist the prioritization of candidate BGC.

Biosynthesis of bioactive natural products from Basidiomycota.

The Basidiomycota, also called club fungi, comprise a diverse group of fungi. Basidiomycota are strongly related to ecosystem functioning along with human life. These fungi display a wide range of bioactivities, and some are known to produce of deadly toxins or hallucinogens. Some Basidiomycota have be used as medicinal mushrooms for thousands of years. Recently, the biosyntheses of several classes of natural products from Basidiomycota have been reported. Here, we review recent studies on the biosynthetic pathways and enzymes of bioactive natural products from Basidiomycota fungi, with a focus on terpenoids, alkaloids, ribosomally synthesized and post-translationally modified peptides (RiPPs), and polyketides.

RV-59 suppresses cytoplasmic Nrf2-mediated 5-fluorouracil resistance and tumor growth in colorectal cancer.

Our previous studies indicated that tumor invasion and 5-flurouracil (5-FU) resistance in colorectal cancer (CRC) was more affected by cytoplasmic localization of expressed Nrf2 (cNrf2) than by nuclear localization (nNrf2), indicating a need for novel antitumor agents to overcome 5-FU resistance and improve outcomes in patients with CRC. In the present study, 20 nitrogen-substituted anthra[1,2-c][1,2,5] thiadiazole-6,11-dione derivatives were collected to verify the compound most able to suppress cell growth in nuclear location sequence (NLS)-mutated Nrf2-transfected shNrf2-HCT116 stable clones that have high cNrf2 expression. The MTT assay indicated that these high-cNrf2-expressing shNrf2-HCT116 stable clones exhibited the lowest percentage survival when treated with RV-59 than with the other 19 compounds. As expected, the high-cNrf2-expressing cells also showed a higher value for the inhibitory concentration of 50% cell survival (IC50) for 5-FU when compared with Nrf2-knockdown HCT116 stable clones (17.74 µM vs. 5.34 µM). Interestingly, a lower RV-59 IC50 value was seen in the high-cNrf2-expressing stable clones than in the Nrf2-knockdown stable clones (3.55 µM vs. 16.81 µM). A similar low RV-59 IC50 value was observed in high-cNrf2-expressing NLS-mutated Nrf2-transfected shNrf2-HCT116 stable clones and p53 null (-/-) HCT116 cells (4.2 µM vs. 4.4 µM), whereas the IC50 value was 17.6 µM in normal colon FHC epithelial cells. Colony-forming assays confirmed that RV-59 treatment inhibited colony formation in NLS-mutated Nrf2-transfected shNrf2-HCT116 stable clones and in p53-/- HCT116 cells. Annexin-V/PI staining showed an involvement of apoptosis in the inhibitory effect of RV-59 on cell viability. A nude mouse xenograft tumor model showed that RV-59 efficiently suppressed tumor growth induced by transplanted NLS-mutated Nrf2-transfected shNrf2-HCT116 stable clones without affecting the body weight of the nude mice over the 37 day experimental period. These results strongly suggest that RV-59 may be a novel antitumor agent for suppression of 5-FU resistance and may have therapeutic potential for improving outcomes in patients with cNrf2-expressing tumors.

HEx: A heterologous expression platform for the discovery of fungal natural products.

For decades, fungi have been a source of U.S. Food and Drug Administration-approved natural products such as penicillin, cyclosporine, and the statins. Recent breakthroughs in DNA sequencing suggest that millions of fungal species exist on Earth, with each genome encoding pathways capable of generating as many as dozens of natural products. However, the majority of encoded molecules are difficult or impossible to access because the organisms are uncultivable or the genes are transcriptionally silent. To overcome this bottleneck in natural product discovery, we developed the HEx (Heterologous EXpression) synthetic biology platform for rapid, scalable expression of fungal biosynthetic genes and their encoded metabolites in Saccharomyces cerevisiae. We applied this platform to 41 fungal biosynthetic gene clusters from diverse fungal species from around the world, 22 of which produced detectable compounds. These included novel compounds with unexpected biosynthetic origins, particularly from poorly studied species. This result establishes the HEx platform for rapid discovery of natural products from any fungal species, even those that are uncultivable, and opens the door to discovery of the next generation of natural products.

Biosynthesis of Complex Indole Alkaloids: Elucidation of the Concise Pathway of Okaramines.

The okaramines are a class of complex indole alkaloids isolated from Penicillium and Aspergillus species. Their potent insecticidal activity arises from selectively activating glutamate-gated chloride channels (GluCls) in invertebrates, not affecting human ligand-gated anion channels. Okaramines B (1) and D (2) contain a polycyclic skeleton, including an azocine ring and an unprecedented 2-dimethyl-3-methyl-azetidine ring. Owing to their complex scaffold, okaramines have inspired many total synthesis efforts, but the enzymology of the okaramine biosynthetic pathway remains unexplored. Here, we identified and characterized the biosynthetic gene cluster (oka) of 1 and 2, then elucidated the pathway with target gene inactivation, heterologous reconstitution, and biochemical characterization. Notably, we characterized an α-ketoglutarate-dependent non-heme FeII dioxygenase that forged the azetidine ring on the okaramine skeleton.