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Background: The increasing prevalence of drug-resistant tuberculosis (TB) underscores the urgent need for novel antimicrobial agents. Methods: This study integrates cultivation optimization, nuclear magnetic resonance (NMR) fingerprinting, and principal component analysis (PCA) to explore microbial secondary metabolites as potential anti-TB agents. Results: Using the combined approach, 11 bioactive compounds were isolated and identified, all exhibiting anti-Mycobacterium bovis BCG activity. Notable findings include borrelidin, a potent threonyl-tRNA synthetase inhibitor with broad biological activities, and L-O-Lac-L-Val-D-O-Hiv-D-Val, a peptide isolated for the first time from a plant endophyte, demonstrating broad-spectrum antimicrobial activity. Additionally, elaiophylin and polycyclic tetramate macrolactams (PTMs) displayed significant bactericidal effects, with elaiophylin achieving complete BCG inhibition at 72 h and PTMs marking their first reported anti-TB activity. The study also identified bafilomycins as potent scaffolds for anti-TB drug development, showcasing rapid bactericidal activity at low MIC values. Conclusions: These findings emphasize the value of microbial metabolites as a reservoir of bioactive compounds and provide new avenues for developing next-generation anti-TB therapies. [ABSTRACT FROM AUTHOR]

Background: The increasing prevalence of drug-resistant tuberculosis (TB) underscores the urgent need for novel antimicrobial agents. Methods: This study integrates cultivation optimization, nuclear magnetic resonance (NMR) fingerprinting, and principal component analysis (PCA) to explore microbial secondary metabolites as potential anti-TB agents. Results: Using the combined approach, 11 bioactive compounds were isolated and identified, all exhibiting anti-Mycobacterium bovis BCG activity. Notable findings include borrelidin, a potent threonyl-tRNA synthetase inhibitor with broad biological activities, and L-O-Lac-L-Val-D-O-Hiv-D-Val, a peptide isolated for the first time from a plant endophyte, demonstrating broad-spectrum antimicrobial activity. Additionally, elaiophylin and polycyclic tetramate macrolactams (PTMs) displayed significant bactericidal effects, with elaiophylin achieving complete BCG inhibition at 72 h and PTMs marking their first reported anti-TB activity. The study also identified bafilomycins as potent scaffolds for anti-TB drug development, showcasing rapid bactericidal activity at low MIC values. Conclusions: These findings emphasize the value of microbial metabolites as a reservoir of bioactive compounds and provide new avenues for developing next-generation anti-TB therapies.

It is important to improve the production of bioactive secondary products for drug development. The Escherichia coli—Streptomyces shuttle vector pSET152 and its derived vector pIB139 containing a strong constitutive promoter ermEp* are commonly used as integrative vectors in actinomycetes. Four new integrative vectors carrying the strong constitutive promoter kasOp*, hrdBp, SCO5768p, and SP44, respectively, were constructed and proven to be functional in different mangrove-derived Streptomyces host strains by using kanamycin resistance gene neo as a reporter. Some biosynthetic genes of elaiophylins, azalomycin Fs, and armeniaspirols were selected and inserted into these vectors to overexpress in their producers including Streptomyces sp. 219807, Streptomyces sp. 211726, and S. armeniacus DSM 43125, resulting in an approximately 1.1–1.4-fold enhancement of the antibiotic yields. [ABSTRACT FROM AUTHOR]

Pancreatic cancer remains a formidable challenge in oncology due to its aggressive nature and limited treatment options. In this study, we investigate the potential therapeutic efficacy of elaiophylin, a novel compound, in targeting BxPC-3 and PANC-1 pancreatic cancer cells. We comprehensively explore elaiophylin's impact on apoptosis induction, proliferation inhibition, migration suppression, invasion attenuation, and angiogenesis inhibition, key processes contributing to cancer progression and metastasis. The results demonstrate that elaiophylin exerts potent pro-apoptotic effects, inducing a substantial increase in apoptotic cells. Additionally, elaiophylin significantly inhibits proliferation, migration, and invasion of BxPC-3 and PANC-1 cells. Furthermore, elaiophylin exhibits remarkable anti-angiogenic activity, effectively disrupting tube formation in HUVECs. Moreover, elaiophylin significantly inhibits the Wnt/β-Catenin signaling pathway. Our findings collectively demonstrate the multifaceted potential of elaiophylin as a promising therapeutic agent against pancreatic cancer via inhibition of the Wnt/β-Catenin signaling pathway. By targeting diverse cellular processes crucial for cancer progression, elaiophylin emerges as a prospective candidate for future targeted therapies. Further investigation of the in vivo efficacy of elaiophylin is warranted, potentially paving the way for novel and effective treatment approaches in pancreatic cancer management. [ABSTRACT FROM AUTHOR]

Prostate cancer (PCa) patients who progress to metastatic castration-resistant PCa (mCRPC) mostly have poor outcomes due to the lack of effective therapies. Our recent study established the orphan nuclear receptor RORγ as a novel therapeutic target for CRPC. Here, we reveal that elaiophylin (Elai), an antibiotic from Actinomycete streptomyces, is a novel RORγ antagonist and showed potent antitumor activity against CRPC in vitro and in vivo. We demonstrated that Elai selectively binded to RORγ protein and potently blocked RORγ transcriptional regulation activities. Structure-activity relationship studies showed that Elai occupied the binding pocket with several key interactions. Furthermore, Elai markedly reduced the recruitment of RORγ to its genomic DNA response element (RORE), suppressed the expression of RORγ target genes AR and AR variants, and significantly inhibited PCa cell growth. Importantly, Elai strongly suppressed tumor growth in both cell line based and patient-derived PCa xenograft models. Taken together, these results suggest that Elai is novel therapeutic RORγ inhibitor that can be used as a drug candidate for the treatment of human CRPC.

It is important to improve the production of bioactive secondary products for drug development. The Escherichia coli—Streptomyces shuttle vector pSET152 and its derived vector pIB139 containing a strong constitutive promoter ermEp* are commonly used as integrative vectors in actinomycetes. Four new integrative vectors carrying the strong constitutive promoter kasOp*, hrdBp, SCO5768p, and SP44, respectively, were constructed and proven to be functional in different mangrove-derived Streptomyces host strains by using kanamycin resistance gene neo as a reporter. Some biosynthetic genes of elaiophylins, azalomycin Fs, and armeniaspirols were selected and inserted into these vectors to overexpress in their producers including Streptomyces sp. 219807, Streptomyces sp. 211726, and S. armeniacus DSM 43125, resulting in an approximately 1.1–1.4-fold enhancement of the antibiotic yields.

Simple Summary: Lung adenocarcinoma (LADC) is the pathological type with the highest morbidity and mortality among lung cancers. Although achievements in new therapeutic approaches have been developed, chemotherapy is still the most widely choice for control of LADC. However, the increasing drug resistance becomes the major challenge, so the development of the novel and efficient chemotherapeutic drug is still urgent. Elaiophylin, a new type of autophagy inhibitor, has been shown to possess unique anti-cancer activity. In this study, we have deeply investigated the therapeutic effect of elaiophylin on LADC and found elaiophylin exerts its anti-cancer effect though inhibiting mitophagy and oxidative stress and targeting SIRT1/Nrf2 signaling. This innovative and comprehensive research may provide the possibility for the development of novel chemotherapy drug for LADC. Lung adenocarcinoma (LADC), the most common type of lung cancer, is still one of the most aggressive and rapidly fatal tumor types, even though achievements in new therapeutic approaches have been developed. Elaiophylin as a C2 symmetrically glycosylated 16 macrolides has been reported to be a late-stage autophagy inhibitor with a potent anti-tumor effect on various cancers. This study investigated the anti-tumor effect of elaiophylin on human LADC for the first time in in vitro and in vivo models. The in vitro study in LADC A549 cells showed that elaiophylin significantly inhibited cell viability and induced cell apoptosis through the suppression of mitophagy and induction of cellular and mitochondrial oxidative stress. Proteomic analysis and molecular docking assay implicated that SIRT1 was likely the direct target of elaiophylin in A549 cells. Further mechanistic study verified that elaiophylin reduced Nrf2 deacetylation, expression, and transcriptional activity as well as cytoplasm translocation by downregulating SIRT1 expression and deacetylase activity. Additionally, SIRT1/Nrf2 activation could attenuate elaiophylin-induced mitophagy inhibition and oxidative stress. The in vivo study in the A549-xenograft mice model showed that the anti-tumor effect of elaiophylin was accompanied by the decreased expressions of SIRT1, Nrf2, Parkin, and PINK1. Thus, the present study reports that elaiophylin has potent anti-tumor properties in LADC, which effect is likely mediated through suppressing the SIRT1/Nrf2 signaling. In conclusion, elaiophylin may be a novel drug candidate for LADC and SIRT1 may be a new therapeutic target for such devastating malignancy. [ABSTRACT FROM AUTHOR]

Elaiophylin (Ela), a unique 16‐membered symmetric macrodiolide antibiotic, displays broad biological activity. Two rare 2‐deoxy‐l‐fucose moieties at the ends of Ela are critical for its activity. Previously, elaiophylin glycosyltransferase (ElaGT) was identified as the enzyme that is responsible for the symmetric glycosylation of Ela, acting as a potential enzymatic tool for enhancing the diversity and activity of Ela. However, a symmetric catalytic mechanism has never been reported for a glycosyltransferase (GT). To explore the catalytic mechanism, the structure of ElaGT was determined in four forms: the apo form and Ela‐bound, thymidine diphosphate‐bound and uridine diphosphate‐bound forms. In the Ela‐bound structure, two ElaGTs form a 'face‐to‐face' C2‐symmetric homodimer with a continuous acceptor‐binding pocket, allowing a molecule of Ela to shuffle through. Interestingly, this dimer interface resembles that of the activator‐dependent GT EryCIII with its activator EryCII. Sequence analysis also indicates that ElaGT belongs to the activator‐dependent GT family, but no putative activator has been identified in the Ela gene cluster. It was then found that the ElaGT homodimer may utilize this 'face‐to‐face' arrangement to stabilize the Ela‐binding loops on the interface and to simultaneously allosterically regulate the catalytic center. Therefore, these structures present a novel self‐activating model for symmetric sugar transfer in the GT family and a new potential regulation site for substrate specificity. [ABSTRACT FROM AUTHOR]

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, which is associated with poor prognosis. Up to 50% of UM patients develop metastasis. Therapeutics that have proven effective in cutaneous melanoma have little success in treating UM, possibly due to its low mutational burden. Therefore, new drug therapies are highly desired for UM. Our in vitro studies showed that Elaiophylin, a late-stage autophagy inhibitor, exhibited an outstanding anticancer activity in human UM cell lines and human UM primary cells through suppressing mitophagy, inducing oxidative stress and leading to autophagic cell death. Our mechanistic study revealed that Elaiophylin exerted its effect by down-regulating SIRT1 and thus influencing deacetylation and mitochondrial localization of FoxO3a. In our confirmatory experiments, SRT1720, a SIRT1 specific activator, could attenuate Elaiophylin-induced inhibition of mitophagy and elevation of oxidative stress, and such effects was partly reversed by FoxO3a knockdown. Our further in vivo studies showed that Elaiophylin dramatically inhibited tumor growth in the human UM xenograft mouse model, which was accompanied with a decreased SIRT1 expression. Thus, the current study is the first to demonstrate that Elaiophylin has a potent anti-cancer effect against UM, which activity is possibly mediated through regulating SIRT1-FoxO3a signaling axis. And Elaiophylin may be a new and promising drug candidate to treat human UM. [ABSTRACT FROM AUTHOR]

Rapamycin is an important macrocyclic antibiotic produced by Streptomyces rapamycinicus. In the rapamycin biosynthetic gene cluster (BGC), there are up to five regulatory genes, which have been shown to play important roles in the regulation of rapamycin biosynthesis. Here, we demonstrated that the rapamycin BGC-situated LAL family regulator RapH co-ordinately regulated the biosynthesis of both rapamycin and elaiophylin. We showed that rapH overexpression not only resulted in enhanced rapamycin production but also led to increased synthesis of another type I polyketide antibiotic, elaiophylin. Consistent with this, rapH deletion resulted in decreased production of both antibiotics. Through real-time RT-PCR combined with β-glucuronidase reporter assays, four target genes controlled by RapH, including rapL (encoding a lysine cyclodeaminase)/rapH in the rapamycin BGC and ela3 (encoding a LuxR family regulator)/ela9 (encoding a hypothetical protein) in the elaiophylin BGC, were identified. A relatively conserved signature sequence recognized by RapH, which comprises two 4-nt inverted repeats separated by 8-nt, 5′-GTT/AC-N8-GTAC-3′, was defined. Taken together, our findings demonstrated that RapH was involved in co-ordinated regulation of two disparate BGCs specifying two unrelated antibiotics, rapamycin and elaiophylin. These results further expand our knowledge of the regulation of antibiotic biosynthesis in S. rapamycinicus. Key points: • The cluster-situated regulator RapH controlled the synthesis of two antibiotics. • Four promoter regions recognized by RapH were identified. • A 16-nt signature DNA sequence essential for RapH regulation was defined. [ABSTRACT FROM AUTHOR]

Prostate cancer (PCa) patients who progress to metastatic castration-resistant PCa (mCRPC) mostly have poor outcomes due to the lack of effective therapies. Our recent study established the orphan nuclear receptor RORγ as a novel therapeutic target for CRPC. Here, we reveal that elaiophylin (Elai), an antibiotic from Actinomycete streptomyces, is a novel RORγ antagonist and showed potent antitumor activity against CRPC in vitro and in vivo. We demonstrated that Elai selectively binded to RORγ protein and potently blocked RORγ transcriptional regulation activities. Structure–activity relationship studies showed that Elai occupied the binding pocket with several key interactions. Furthermore, Elai markedly reduced the recruitment of RORγ to its genomic DNA response element (RORE), suppressed the expression of RORγ target genes AR and AR variants, and significantly inhibited PCa cell growth. Importantly, Elai strongly suppressed tumor growth in both cell line based and patient-derived PCa xenograft models. Taken together, these results suggest that Elai is novel therapeutic RORγ inhibitor that can be used as a drug candidate for the treatment of human CRPC.

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, which is associated with poor prognosis. Up to 50% of UM patients develop metastasis. Therapeutics that have proven effective in cutaneous melanoma have little success in treating UM, possibly due to its low mutational burden. Therefore, new drug therapies are highly desired for UM. Our in vitro studies showed that Elaiophylin, a late-stage autophagy inhibitor, exhibited an outstanding anticancer activity in human UM cell lines and human UM primary cells through suppressing mitophagy, inducing oxidative stress and leading to autophagic cell death. Our mechanistic study revealed that Elaiophylin exerted its effect by down-regulating SIRT1 and thus influencing deacetylation and mitochondrial localization of FoxO3a. In our confirmatory experiments, SRT1720, a SIRT1 specific activator, could attenuate Elaiophylin-induced inhibition of mitophagy and elevation of oxidative stress, and such effects was partly reversed by FoxO3a knockdown. Our further in vivo studies showed that Elaiophylin dramatically inhibited tumor growth in the human UM xenograft mouse model, which was accompanied with a decreased SIRT1 expression. Thus, the current study is the first to demonstrate that Elaiophylin has a potent anti-cancer effect against UM, which activity is possibly mediated through regulating SIRT1-FoxO3a signaling axis. And Elaiophylin may be a new and promising drug candidate to treat human UM.

Two new elaiophylin derivatives, efomycins K (1) and L (2), and five known elaiophylin derivatives (3–7) were isolated from the termite-associated Streptomyces sp. M56. The structures were determined by 1D and 2D NMR and HR-ESIMS analyses and comparative CD spectroscopy. The putative gene cluster responsible for the production of the elaiophylin and efomycin derivatives was identified based on significant homology to related clusters. Phylogenetic analysis of gene cluster domains was used to provide a biosynthetic rational for these new derivatives and to demonstrate how a single biosynthetic pathway can produce diverse structures.

Two new elaiophylin derivatives, efomycins K (1) and L (2), and five known elaiophylin derivatives (3–7) were isolated from the termite-associated Streptomyces sp. M56. The structures were determined by 1D and 2D NMR and HR-ESIMS analyses and comparative CD spectroscopy. The putative gene cluster responsible for the production of the elaiophylin and efomycin derivatives was identified based on significant homology to related clusters. Phylogenetic analysis of gene cluster domains was used to provide a biosynthetic rational for these new derivatives and to demonstrate how a single biosynthetic pathway can produce diverse structures. [ABSTRACT FROM AUTHOR]

Angiogenesis plays a very important role in tumor progression through the creation of new blood vessels. Therefore, angiogenesis inhibitors could contribute to cancer treatment. Here, we show that a microbial metabolite, elaiophylin, exhibits potent antiangiogenic activity from in vitro and in vivo angiogenesis assays. Elaiophylin dramatically suppressed in vitro angiogenic characteristics such as proliferation, migration, adhesion, invasion and tube formation of human umbilical vein endothelial cells (HUVECs) stimulated by vascular endothelial growth factor (VEGF) at non-toxic concentrations. In addition, elaiophylin immensely inhibited in vivo angiogenesis of the chorioallantoic membrane (CAM) from growing chick embryos without cytotoxicity. The activation of VEGF receptor 2 (VEGFR2) in HUVECs by VEGF was inhibited by elaiophylin, resulting in the suppression of VEGF-induced activation of downstream signaling molecules, Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, nuclear factor-κB (NFκB), matrix metalloproteinase (MMP)-2 and -9 which are closely associated with VEGF-induced angiogenesis. We also found that elaiophylin blocked tumor cell-induced angiogenesis both in vitro and in vivo. Elaiophylin downregulated the expression of VEGF by inhibiting hypoxia inducible factor-1α (HIF-1α) accumulation in tumor cells. To our knowledge, these results for the first time demonstrate that elaiophylin effectively inhibits angiogenesis and thus may be utilized as a new class of natural antiangiogenic agent for cancer therapy. [ABSTRACT FROM AUTHOR]

Elaiophylins belong to a special family of 16-membered macrodiolides with C2-symmetry. They have exhibited remarkable biological activities, such as antimicrobial, anthelmintic, anticancer, immunosuppressive, anti-inflammatory, antiviral, and α-glucosidase inhibitory activities. A member of elaiophylins, efomycin M, is as a specific small molecule inhibitor of selectin in preclinical trial for the treatment of psoriasis, ischemia-reperfusion, and allergy. The biosynthetic investigation of elaiophylins has uncovered a unique thioesterase, which is responsible for the formation of C2-symmetric diolide. We herein summarize the natural occurrence, bioactivity, and biosynthesis of elaiophylins covering the literatures from 1959 to 2019. Hopefully, this review will inspire further research interests of these compounds and encourage the discovery of new analogues by metabolic engineering or genome mining.

Elaiophylin is a natural compound and a novel and potent inhibitor of late stage autophagy with outstanding antitumor activity in human ovarian cancer cells. However, the possible biologic effects and functional linkage between elaiophylin and multiple myeloma (MM) have not been explored. This study aimed to assess the effect of elaiophylin on MM cells with mutant TP53 and the possible molecular mechanism. The results suggested that elaiophylin exerted anti-myeloma activity by inducing apoptosis and proliferation arrest. As expected, elaiophylin blocked autophagy flux in MM cells. Subsequently, persistent activation of endoplasmic reticulum (ER) stress was induced. Moreover, the apoptotic effect was to some extent attenuated by the ER stress inhibitor tauroursodeoxycholic acid (TUDCA). Further studies indicated that elaiophylin effectively suppressed MM cell growth without obvious side effects in zebrafish embryo and mouse xenograft models. Taken together, our data are the first to demonstrate that exposure of human MM cells with mutant TP53 to elaiophylin blocked autophagy flux and thus induced cell death, which partially involved ER stress-associated apoptosis. Targeted disruption of the cellular protein handling system by elaiophylin is therefore a promising therapeutic strategy for overcoming incurable MM, even when TP53 mutations are present. [ABSTRACT FROM PUBLISHER]

Actinomycetes are known to produce numerous secondary bioactive metabolites of pharmaceutical interest. The purpose of this study was to isolate, characterize, and investigate the antibacterial, antifungal, and anticancer activities of metabolites produced by Actinobacteria isolated from the rhizosphere of Paullinia cupana. The Actinobacteria was identified as Streptomyces hygroscopicus ACTMS-9H. Based on a bioguided study, the methanolic biomass extract obtained from submerged cultivation had the most potent antibacterial, antifungal, and cytotoxic activities. This extract was partitioned with n-hexane, ethyl acetate, and 2-butanol. Elaiophylin was isolated from the methanolic biomass extract, and its molecular formula was determined (CHO) based on H and C NMR, IR and MS analyses. The 2-butanol phase was fractionated into four fractions (EB1, EB2A, EB2B, and EB3M). Chemical prospecting indicated the presence of alkaloids, saponins, and reducing sugars in the methanolic extract and 2-butanol phase. The elaiophylin displayed anticancer activity in HEp-2 and HL-60 cells with an IC of 1 μg/mL. The EB1 fraction was selectively toxic to HL-60 cells with IC of 9 ng/mL. Bioautography showed that the EB1 fraction contained an alkaloid with antibacterial and antifungal activities (MIC values ≤1.9 and <3.9 μg/mL, respectively). In conclusion, the EB1 fraction and elaiophylin of S. hygroscopicus have potent antimicrobial, antifungal, and anticancer activities. [ABSTRACT FROM AUTHOR]

During our search for interesting bioactive secondary metabolites from mangrove actinomycetes, the strain Streptomyces sp. 219807 which produced a high elaiophylin yield of 4486 mg/L was obtained. A new elaiophylin derivative, halichoblelide D (1), along with seven known analogues 2-8 was isolated and identified from the culture broth. Their chemical structures were determined by detailed analysis of 1D and 2D NMR and HRMS data. The absolute configuration of halichoblelide D (1) was confirmed by comparing the CD spectrum with those of the reported analogues. Compounds 1-7 exhibited potent cytotoxic activities against HeLa and MCF-7 cells with IC50 values ranging from 0.19 to 2.12 μM. [ABSTRACT FROM AUTHOR]

The stereoselective synthesis of key fragments 3 and 7 of elaiophylin has been accomplished from readily available epichlorohydrin as the starting material. The key reactions involved are Jacobsen's kinetic resolution, Prins cyclization, pyridinium chlorochromate-mediated oxidative cleavage, Grignard reaction, and cross-metathesis reaction. [ABSTRACT FROM AUTHOR]

Elaiophylin is an unusual C2-symmetric antibiotic macrodiolide produced on a bacterial modular polyketide synthase assembly line. To probe the mechanism and selectivity of diolide formation, we sought to reconstitute ring formation in vitro by using a non-natural substrate. Incubation of recombinant elaiophylin thioesterase/cyclase with a synthetic pentaketide analogue of the presumed monomeric polyketide precursor of elaiophylin, specifically its N-acetylcysteamine thioester, produced a novel 16-membered C2-symmetric macrodiolide. A linear dimeric thioester is an intermediate in ring formation, which indicates iterative use of the thioesterase active site in ligation and subsequent cyclization. Furthermore, the elaiophylin thioesterase acts on a mixture of pentaketide and tetraketide thioesters to give both the symmetric decaketide diolide and the novel asymmetric hybrid nonaketide diolide. Such thioesterases have potential as tools for the in vitro construction of novel diolides. [ABSTRACT FROM AUTHOR]

The impact of different carbon sources on the antibiotic production by Streptomyces hygroscopicus CH-7 was studied with the main goal to increase the yield of antibiotics hexaene H-85 and elaiophylin. Glucose, as a basic carbon source in the nutrition medium, was replaced with glycerol, xylose, sorbose, melibiose, inulin, and mannitol (15 g/dm). Insuring the maximum yields of hexaene and elaiophylin of 192 and 88 μg/cm, respectively, glycerol was shown to be the best carbon source among the investigated ones. [ABSTRACT FROM AUTHOR]

A type I PKS gene probe obtained from RAPB of the rapamycin producer Streptomyces hygroscopicus, strongly hybridised to 92 out of 1120 cosmids from a genomic library of the elaiophylin-producing strain Streptomyces sp. DSM4137. Partial cosmid sequencing suggested the presence of 10 separate sequences encoding type I PKS genes. One entire DNA sequence was obtained and found exactly to match the gene organisation expected for the biosynthesis of the unusual macrodiolide polyketide elaiophylin. The putative elaiophylin gene cluster contains five large open-reading frames encoding typical modular polyketide synthases, which together catalyse the synthesis of the octaketide monomer of elaiophylin. Other genes were identified that would be required for provision of the ethylmalonate extender unit, for the synthesis and attachment of 2-deoxy-l-fucose and in regulation, or in export of the product. Immediately adjacent to the putative elaiophylin biosynthetic gene cluster is a 30-kbp region containing the gene for adenosylcobalamin-dependent methylmalonyl CoA mutase and also genes involved in the biosynthesis of the cobalamin cofactor. Analysis of the latter gene set confirms the view that cbiD of the anaerobic pathway and cobF in the aerobic pathway catalyse the same methylation of precorrin-5. The proximity of these genes to the putative elaiophylin gene cluster can best be rationalised if in this organism succinyl-CoA is a significant source of the methylmalonate units for complex polyketide biosynthesis. [Copyright &y& Elsevier]

Elaiophylins belong to a special family of 16-membered macrodiolides with C2-symmetry. They have exhibited remarkable biological activities, such as antimicrobial, anthelmintic, anticancer, immunosuppressive, anti-inflammatory, antiviral, and α-glucosidase inhibitory activities. A member of elaiophylins, efomycin M, is as a specific small molecule inhibitor of selectin in preclinical trial for the treatment of psoriasis, ischemia-reperfusion, and allergy. The biosynthetic investigation of elaiophylins has uncovered a unique thioesterase, which is responsible for the formation of C2-symmetric diolide. We herein summarize the natural occurrence, bioactivity, and biosynthesis of elaiophylins covering the literatures from 1959 to 2019. Hopefully, this review will inspire further research interests of these compounds and encourage the discovery of new analogues by metabolic engineering or genome mining. [ABSTRACT FROM AUTHOR]