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Journal articles on the topic 'Lactones – Synthèse'

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Published: 4 June 2021
Last updated: 25 May 2024

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1

Caille, Jean Claude, Michel Farnier, Roger Guilard, André Aubry, and Claude Lecomte. "Sur une nouvelle méthode de synthèse de δ-lactones cyclopenténiques." Canadian Journal of Chemistry 64, no. 4 (April 1, 1986): 831–36. http://dx.doi.org/10.1139/v86-136.

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Synthesis of two cyclopentenic δ-lactones, 1,3,4,4a,5,6-hexahydrocyclopenta[c]pyran-1-one and its analogue possessing a cyclopentenyl group bonded to the carbon atom 4a is described, starting from the cyclopentanone or cyclopentylidene cyclopentanone. The remarkable reactivity of the tosylhydrazones allows transformation of these compounds into substituted cyclopentenes, which lead to δ-lactones by cyclization. The conditions of cyclization depend on the nature of the cyclopentanone. The structure of the two δ-lactones is established by 1H and 13C nmr data, mass spectrometry, and, in one case, by X-ray analysis.
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2

Ulrich, Ricky L. "Quorum Quenching: Enzymatic Disruption of N-Acylhomoserine Lactone-Mediated Bacterial Communication in Burkholderia thailandensis." Applied and Environmental Microbiology 70, no. 10 (October 2004): 6173–80. http://dx.doi.org/10.1128/aem.70.10.6173-6180.2004.

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ABSTRACT Many species of gram-negative bacteria communicate by synthesizing, secreting, and responding to N-acylhomoserine lactones (AHLs), a mechanism termed quorum sensing. Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates of Bacillus spp. The Burkholderia thailandensis quorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins. Expression of the Bacillus anthracis (Ames strain) AiiA lactonase in B. thailandensis completely abolished the accumulation of N-decanoylhomoserine lactone (C10-HSL) and N-octanoylhomoserine lactone (C8-HSL), reduced N-hexanoylhomoserine lactone (C6-HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism. In contrast, heterologous expression of the Bacillus cereus strain A24 AiiA lactonase in B. thailandensis reduced the concentrations of C6-HSL, C8-HSL, and C10-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization. Individual disruption of the B. thailandensis AHSs, specifically disruption of the btaI1 and btaI3 genes, which encode the proteins that direct the synthesis of C8-HSL and C6-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity. The results of this study demonstrate that heterologous expression of Bacillus sp. AiiA lactonases in B. thailandensis reduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the beta-hemolysis of sheep erythrocytes.
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3

Xu, Yuquan, Patricia Espinosa-Artiles, Vivien Schubert, Ya-ming Xu, Wei Zhang, Min Lin, A. A. Leslie Gunatilaka, Roderich Süssmuth, and István Molnár. "Characterization of the Biosynthetic Genes for 10,11-Dehydrocurvularin, a Heat Shock Response-Modulating Anticancer Fungal Polyketide from Aspergillus terreus." Applied and Environmental Microbiology 79, no. 6 (January 18, 2013): 2038–47. http://dx.doi.org/10.1128/aem.03334-12.

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ABSTRACT10,11-Dehydrocurvularin is a prevalent fungal phytotoxin with heat shock response and immune-modulatory activities. It features a dihydroxyphenylacetic acid lactone polyketide framework with structural similarities to resorcylic acid lactones like radicicol or zearalenone. A genomic locus was identified from the dehydrocurvularin producer strainAspergillus terreusAH-02-30-F7 to reveal genes encoding a pair of iterative polyketide synthases (A. terreusCURS1 [AtCURS1] and AtCURS2) that are predicted to collaborate in the biosynthesis of 10,11-dehydrocurvularin. Additional genes in this locus encode putative proteins that may be involved in the export of the compound from the cell and in the transcriptional regulation of the cluster. 10,11-Dehydrocurvularin biosynthesis was reconstituted inSaccharomyces cerevisiaeby heterologous expression of the polyketide synthases. Bioinformatic analysis of the highly reducing polyketide synthase AtCURS1 and the nonreducing polyketide synthase AtCURS2 highlights crucial biosynthetic programming differences compared to similar synthases involved in resorcylic acid lactone biosynthesis. These differences lead to the synthesis of a predicted tetraketide starter unit that forms part of the 12-membered lactone ring of dehydrocurvularin, as opposed to the penta- or hexaketide starters in the 14-membered rings of resorcylic acid lactones. TetraketideN-acetylcysteamine thioester analogues of the starter unit were shown to support the biosynthesis of dehydrocurvularin and its analogues, with yeast expressing AtCURS2 alone. Differential programming of the product template domain of the nonreducing polyketide synthase AtCURS2 results in an aldol condensation with a different regiospecificity than that of resorcylic acid lactones, yielding the dihydroxyphenylacetic acid scaffold characterized by an S-type cyclization pattern atypical for fungal polyketides.
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4

Ibrahimi, Sanae, Gilles Sauvé, Joslyn Yelle, and El Mokhtar Essassi. "Synthèse racémique et énantiosélective d’énol-lactones et leur évaluation comme inhibiteurs de la protéase du VIH-1." Comptes Rendus Chimie 8, no. 1 (January 2005): 75–83. http://dx.doi.org/10.1016/j.crci.2004.08.002.

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5

Hanzelka, Brian L., Matthew R. Parsek, Dale L. Val, Paul V. Dunlap, John E. Cronan, and E. P. Greenberg. "Acylhomoserine Lactone Synthase Activity of the Vibrio fischeri AinS Protein." Journal of Bacteriology 181, no. 18 (September 15, 1999): 5766–70. http://dx.doi.org/10.1128/jb.181.18.5766-5770.1999.

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ABSTRACT Acylhomoserine lactones, which serve as quorum-sensing signals in gram-negative bacteria, are produced by members of the LuxI family of synthases. LuxI is a Vibrio fischeri enzyme that catalyzes the synthesis of N-(3-oxohexanoyl)-l-homoserine lactone from an acyl-acyl carrier protein andS-adenosylmethionine. Another V. fischeri gene,ainS, directs the synthesis ofN-octanoylhomoserine lactone. The AinS protein shows no significant sequence similarity with LuxI family members, but it does show sequence similarity with the Vibrio harveyi LuxM protein. The luxM gene is required for the synthesis ofN-(3-hydroxybutyryl)-l-homoserine lactone. To gain insights about whether AinS and LuxM represent a second family of acylhomoserine lactone synthases, we have purified AinS as a maltose-binding protein (MBP) fusion protein. The purified MBP-AinS fusion protein catalyzed the synthesis ofN-octanoylhomoserine lactone fromS-adenosylmethionine and either octanoyl-acyl carrier protein or, to a lesser extent, octanoyl coenzyme A. With the exception that octanoyl coenzyme A served as an acyl substrate for the MBP-AinS fusion protein, the substrates for and reaction kinetics of the MBP-AinS fusion protein were similar to those of the several LuxI family members previously studied. We conclude that AinS is an acylhomoserine lactone synthase and that it represents a second family of such enzymes.
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6

Dancewicz, Katarzyna, Antoni Szumny, Czesław Wawrzeńczyk, and Beata Gabryś. "Repellent and Antifeedant Activities of Citral-Derived Lactones against the Peach Potato Aphid." International Journal of Molecular Sciences 21, no. 21 (October 28, 2020): 8029. http://dx.doi.org/10.3390/ijms21218029.

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Citral is well known for its antimicrobial, antifungal, and insecticidal activities. Natural sesquiterpene α-methylenelactones also exhibit a broad spectrum of biological activities. The aim of the study was to explore the effect of structural changes to citral molecules on citral behavior-modifying activity towards Myzus persicae. Specifically, the effects of the introduction of a γ-lactone moiety and methylene groups in α and γ positions of the lactone ring were investigated. The lactones were obtained in five-step (saturated lactone and γ-methylenelactone) or six-step (α-methylenelactone and α,γ-dimethylenelactone) syntheses from citral. The synthetic procedures and physical and spectral data of the lactones are presented. The settling behavior of freely moving aphids in choice and no-choice situations was monitored. The probing behavior of tethered M. persicae using the Electrical Penetration Graph (EPG) technique was also analyzed. Citral appeared a strong repellent and pre-ingestive and ingestive probing deterrent to M. persicae. The incorporation of a lactone moiety caused the loss of the repellent activity. α-Methylenelactone inhibited aphid settling and probing activities at pre-ingestive and ingestive phases. The saturated γ-lactone and α,γ-dimethylenelactone were the settling post-ingestive deterrents to M. persicae, which did not affect aphid probing activity. γ-Methylenelactone did not affect aphid behavior.
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7

Miyazawa, Takeshi, Brendan J. Fitzgerald, and Adrian T. Keatinge-Clay. "Preparative production of an enantiomeric pair by engineered polyketide synthases." Chemical Communications 57, no. 70 (2021): 8762–65. http://dx.doi.org/10.1039/d1cc03073f.

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Modules from the pikromycin synthase were recombined into engineered synthases that furnish an enantiomeric pair of 2-stereocenter triketide lactones at >99% ee with yields up to 0.39 g per liter of E. coli K207-3 in shake flasks.
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8

Sakagami, Yukari, Naoki Kondo, Yuki Sawayama, Hiroyuki Yamakoshi, and Seiichi Nakamura. "Total Syntheses of Marrubiin and Related Labdane Diterpene Lactones." Molecules 25, no. 7 (April 1, 2020): 1610. http://dx.doi.org/10.3390/molecules25071610.

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Total syntheses of the labdane diterpene lactones marrubiin, marrulibacetal, desertine, marrulibacetal A, marrubasch F, cyllenine C, marrulanic acid, and marrulactone are described. The trans-decalin moiety of these molecules was constructed in a stereoselective manner by a Pauson-Khand reaction, and the resultant cyclopentenone was oxidatively cleaved for formation of the lactone ring. Elongation of the side chain at C9 was achieved by an epoxide-opening reaction with a variety of nucleophiles, and the functional group manipulations completed the syntheses of these natural products. Stereochemistries of desertine could be established by the transformations.
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9

Hong, Hui, Yuhui Sun, Yongjun Zhou, Emily Stephens, Markiyan Samborskyy, and Peter F. Leadlay. "Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase." Beilstein Journal of Organic Chemistry 12 (October 11, 2016): 2164–72. http://dx.doi.org/10.3762/bjoc.12.206.

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The assembly-line synthases that produce bacterial polyketide natural products follow a modular paradigm in which each round of chain extension is catalysed by a different set or module of enzymes. Examples of deviation from this paradigm, in which a module catalyses either multiple extensions or none are of interest from both a mechanistic and an evolutionary viewpoint. We present evidence that in the biosynthesis of the 36-membered macrocyclic aminopolyol lactones (marginolactones) azalomycin and kanchanamycin, isolated respectively from Streptomyces malaysiensis DSM4137 and Streptomyces olivaceus Tü4018, the first extension module catalyses both the first and second cycles of polyketide chain extension. To confirm the integrity of the azl gene cluster, it was cloned intact on a bacterial artificial chromosome and transplanted into the heterologous host strain Streptomyces lividans, which does not possess the genes for marginolactone production. When furnished with 4-guanidinobutyramide, a specific precursor of the azalomycin starter unit, the recombinant S. lividans produced azalomycin, showing that the polyketide synthase genes in the sequenced cluster are sufficient to accomplish formation of the full-length polyketide chain. This provides strong support for module iteration in the azalomycin and kanchanamycin biosynthetic pathways. In contrast, re-sequencing of the gene cluster for biosynthesis of the polyketide β-lactone ebelactone in Streptomyces aburaviensis has shown that, contrary to a recently-published proposal, the ebelactone polyketide synthase faithfully follows the colinear modular paradigm.
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10

Gamage, Akshamal Mihiranga, Guanghou Shui, Markus R. Wenk, and Kim Lee Chua. "N-Octanoylhomoserine lactone signalling mediated by the BpsI–BpsR quorum sensing system plays a major role in biofilm formation of Burkholderia pseudomallei." Microbiology 157, no. 4 (April 1, 2011): 1176–86. http://dx.doi.org/10.1099/mic.0.046540-0.

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The genome of Burkholderia pseudomallei encodes three acylhomoserine lactone (AHL) quorum sensing systems, each comprising an AHL synthase and a signal receptor/regulator. The BpsI–BpsR system produces N-octanoylhomoserine lactone (C8HL) and is positively auto-regulated by its AHL product. The products of the remaining two systems have not been identified. In this study, tandem MS was used to identify and quantify the AHL species produced by three clinical B. pseudomallei isolates – KHW, K96243 and H11 – three isogenic KHW mutants that each contain a null mutation in an AHL synthase gene, and recombinant Escherichia coli heterologously expressing each of the three B. pseudomallei AHL synthase genes. BpsI synthesized predominantly C8HL, which accounted for more than 95 % of the extracellular AHLs produced in stationary-phase KHW cultures. The major products of BpsI2 and BpsI3 were N-(3-hydroxy-octanoyl)homoserine lactone (OHC8HL) and N-(3-hydroxy-decanoyl)homoserine lactone, respectively, and their corresponding transcriptional regulators, BpsR2 and BpsR3, were capable of driving reporter gene expression in the presence of these cognate lactones. Formation of biofilm by B. pseudomallei KHW was severely impaired in mutants lacking either BpsI or BpsR but could be restored to near wild-type levels by exogenous C8HL. BpsI2 was not required, and BpsI3 was partially required for biofilm formation. Unlike the bpsI mutant, biofilm formation in the bpsI3 mutant could not be restored to wild-type levels in the presence of OHC8HL, the product of BpsI3. C8HL and OHC8HL had opposite effects on biofilm formation; exogenous C8HL enhanced biofilm formation in both the bpsI3 mutant and wild-type KHW while exogenous OHC8HL suppressed the formation of biofilm in the same strains. We propose that exogenous OHC8HL antagonizes biofilm formation in B. pseudomallei, possibly by competing with endogenous C8HL for binding to BpsR.
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11

Lin, Si-Ting, Chung-Chi Wang, Chi-Jung Chang, Yasuyuki Nakamura, Kun-Yi Andrew Lin, and Chih-Feng Huang. "Progress in the Preparation of Functional and (Bio)Degradable Polymers via Living Polymerizations." International Journal of Molecular Sciences 21, no. 24 (December 16, 2020): 9581. http://dx.doi.org/10.3390/ijms21249581.

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This review presents the latest developments in (bio)degradable approaches and functional aliphatic polyesters and polycarbonates prepared by typical ring-opening polymerization (ROP) of lactones and trimethylene carbonates. It also considers several recent innovative synthetic methods including radical ring-opening polymerization (RROP), atom transfer radical polyaddition (ATRPA), and simultaneous chain- and step-growth radical polymerization (SCSRP) that produce aliphatic polyesters. With regard to (bio)degradable approaches, we have summarized several representative cleavable linkages that make it possible to obtain cleavable polymers. In the section on functional aliphatic polyesters, we explore the syntheses of specific functional lactones, which can be performed by ring-opening copolymerization of typical lactone/lactide monomers. Last but not the least, in the recent innovative methods section, three interesting synthetic methodologies, RROP, ATRPA, and SCSRP are discussed in detail with regard to their reaction mechanisms and polymer functionalities.
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12

Yamamoto, Yuki, Akihiro Tabuchi, Kazumi Hosono, Takanori Ochi, Kento Yamazaki, Shintaro Kodama, Akihiro Nomoto, and Akiya Ogawa. "A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones." Beilstein Journal of Organic Chemistry 17 (December 9, 2021): 2906–14. http://dx.doi.org/10.3762/bjoc.17.198.

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A simple and efficient method for α-brominating lactones that affords α-bromolactones under mild conditions using tetraalkylammonium hydroxide (R4N+OH−) as a base was developed. Lactones are ring-opened with Br2 and a substoichiometric amount of PBr3, leading to good yields of the corresponding α-bromocarboxylic acids. Subsequent intramolecular cyclization over 1 h using a two-phase system (H2O/CHCl3) containing R4N+OH− afforded α-bromo lactones in good yields. This method can be applied at the 10 mmol scale using simple operations. α-Bromo-δ-valerolactone, which is extremely reactive and difficult to isolate, could be isolated and stored in a freezer for about one week using the developed method. Optimizing the solvent for environmentally friendly large-scale syntheses revealed that methyl ethyl ketone (MEK) was as effective. In addition, in situ-generated α-bromo-δ-valerolactone was directly converted into a sulfur-substituted functional lactone without difficulty by reacting it with a sulfur nucleophile in one pot without isolation. This new bromination system is expected to facilitate the industrial use of α-bromolactones as important intermediates.
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13

Martins, Maurilio Lopes, Uelinton Manoel Pinto, Katharina Riedel, and Maria Cristina Dantas Vanetti. "Quorum Sensing and Spoilage Potential of Psychrotrophic Enterobacteriaceae Isolated from Milk." BioMed Research International 2018 (October 22, 2018): 1–13. http://dx.doi.org/10.1155/2018/2723157.

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The 16S rDNA of six psychrotrophic Enterobacteriaceae isolated from cold raw milk were sequenced and the isolate 039 was identified asPantoeasp., isolates 059, 068, and 071 were identified asHafnia alvei, 067 was identified asEnterobactersp., and 099 was identified asAeromonas hydrophila. They presented different spoilage potentials in milk withA. hydrophila099 being the most deteriorative. OnlyPantoeasp. 039 was not able to induce the quorum sensing monitor strains of acyl homoserine lactones (AHLs). ThehalIgene, which encodes the AHL synthase inH. alvei, was identified in the isolates 059, 067, 068, and 071. After initial sequencing characterization and cloning, this gene showed its function by the heterologous synthesis of N-hexanoyl-DL-homoserine lactone and N-3-oxohexanoyl-L-homoserine lactone inEscherichia coli. In addition to producing AHLs,A. hydrophila099 produced AI-2 in higher level than the assay’s positive controlVibrio harveyiBB120. Therefore, Enterobacteriaceae strains isolated from cooled raw milk produce a rich array of signaling molecules that may influence bacterial traits in the milk environment.
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14

Toth, I. K., J. A. Newton, L. J. Hyman, A. K. Lees, M. Daykin, C. Ortori, P. Williams, and R. G. Fray. "Potato Plants Genetically Modified to Produce N-Acylhomoserine Lactones Increase Susceptibility to Soft Rot Erwiniae." Molecular Plant-Microbe Interactions® 17, no. 8 (August 2004): 880–87. http://dx.doi.org/10.1094/mpmi.2004.17.8.880.

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Many gram-negative bacteria employ N-acylhomoserine lactones (AHL) to regulate diverse physiological processes in concert with cell population density (quorum sensing [QS]). In the plant pathogen Erwinia carotovora, the AHL synthesized via the carI/expI genes are responsible for regulating the production of secreted plant cell wall-degrading exoenzymes and the antibiotic carbapen-3-em carboxylic acid. We have previously shown that targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in planta of the cognate AHL signaling molecules N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL), which in turn, were able to complement a carI¯ QS mutant. In the present study, we demonstrate that transgenic potato plants containing the yenI gene are also able to express AHL and that the presence and level of these AHL in the plant increases susceptibility to infection by E. carotovora. Susceptibility is further affected by both the bacterial level and the plant tissue under investigation.
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15

Yu, Kuo, Pengjie Liang, Heshui Yu, Hui Liu, Jialiang Guo, Xiaohui Yan, Zheng Li, Guoqiang Li, Ying Wang, and Chunhua Wang. "Integrating Transcriptome and Chemical Analyses to Provide Insights into Biosynthesis of Terpenoids and Flavonoids in the Medicinal Industrial Crop Andrographis paniculate and Its Antiviral Medicinal Parts." Molecules 29, no. 4 (February 14, 2024): 852. http://dx.doi.org/10.3390/molecules29040852.

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Andrographis paniculata is a medicinal plant traditionally used to produce diterpene lactones and flavonoids, which possess various biological activities. Widely distributed in China, India, and other Southeast Asia countries, A. paniculata has become an important economic crop, significantly treating SARS-CoV-2, and is being cultivated on a large scale in southern China. The biosynthesis of active ingredients in A. paniculata are regulated and controlled by genes, but their specific roles are still not fully understood. To further explore the growth regulation factors and utilization of its medicinal parts of this industrial crop, chemical and transcriptome analyses were conducted on the roots, stems, and leaves of A. paniculata to identify the biosynthesis pathways and related candidate genes of the active ingredients. The chemical analysis revealed that the main components of A. paniculata were diterpene lactones and flavonoids, which displayed potential ability to treat SARS-CoV-2 through molecular docking. Moreover, the transcriptome sequencing annotated a total of 40,850 unigenes, including 7962 differentially expressed genes. Among these, 120 genes were involved in diterpene lactone biosynthesis and 60 genes were involved in flavonoid biosynthesis. The expression of diterpene lactone-related genes was the highest in leaves and the lowest in roots, consistent with our content determination results. It is speculated that these highly expressed genes in leaves may be involved in the biosynthesis pathway of diterpenes. Furthermore, two class Ⅰ terpene synthases in A. paniculata transcriptome were also annotated, providing reference for the downstream pathway of the diterpene lactone biosynthesis. With their excellent market value, our experiments will promote the study of the biosynthetic genes for active ingredients in A. paniculata and provide insights for subsequent in vitro biosynthesis.
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16

Gould, Ty A., Jake Herman, Jessica Krank, Robert C. Murphy, and Mair E. A. Churchill. "Specificity of Acyl-Homoserine Lactone Synthases Examined by Mass Spectrometry." Journal of Bacteriology 188, no. 2 (January 15, 2006): 773–83. http://dx.doi.org/10.1128/jb.188.2.773-783.2006.

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ABSTRACT Many gram-negative bacteria produce a specific set of N-acyl-l-homoserine-lactone (AHL) signaling molecules for the purpose of quorum sensing, which is a means of regulating coordinated gene expression in a cell-density-dependent manner. AHLs are produced from acylated acyl-carrier protein (acyl-ACP) and S-adenosyl-l-methionine by the AHL synthase enzyme. The appearance of specific AHLs is due in large part to the intrinsic specificity of the enzyme for subsets of acyl-ACP substrates. Structural studies of the Pantoea stewartii enzyme EsaI and AHL-sensitive bioassays revealed that threonine 140 in the acyl chain binding pocket directs the enzyme toward production of 3-oxo-homoserine lactones. Mass spectrometry was used to examine the range of AHL molecular species produced by AHL synthases under a variety of conditions. An AHL selective normal-phase chromatographic purification with addition of a deuterated AHL internal standard was followed by reverse-phase liquid chromatography-tandem mass spectrometry in order to obtain estimates of the relative amounts of different AHLs from biological samples. The AHLs produced by wild-type and engineered EsaI and LasI AHL synthases show that intrinsic specificity and different cellular conditions influence the production of AHLs. The threonine at position 140 in EsaI is important for the preference for 3-oxo-acyl-ACPs, but the role of the equivalent threonine in LasI is less clear. In addition, LasI expressed in Escherichia coli produces a high proportion of unusual AHLs with acyl chains consisting of an odd number of carbons. Furthermore, these studies offer additional methods that will be useful for surveying and quantitating AHLs from different sources.
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17

Canonne, P., J. Plamondon, and M. Akssira. "Reactions selectives des organonagnesiens avec les lactols et les lactones. Synthese des diols primaires-secondaires." Tetrahedron 44, no. 10 (January 1988): 2903–12. http://dx.doi.org/10.1016/s0040-4020(88)90027-0.

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18

Canonne, P. "Reactions selectives des organomagnesiens avec les lactols et les lactones Synthese des diols primaires-secondaires." Tetrahedron 44, no. 10 (1988): 2903–12. http://dx.doi.org/10.1016/s0040-4020(01)96238-6.

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19

Spencer, J. B., and P. M. Jordan. "Purification and properties of 6-methylsalicylic acid synthase from Penicillium patulum." Biochemical Journal 288, no. 3 (December 15, 1992): 839–46. http://dx.doi.org/10.1042/bj2880839.

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6-Methylsalicylic acid synthase has been isolated in homogeneous form from Penicillium patulum grown in liquid culture from a spore inoculum. The enzyme is highly susceptible to proteolytic degradation in vivo and in vitro, but may be stabilized during purification by incorporating proteinase inhibitors in the buffers. The enzyme exists as a homotetramer of M(r) 750,000, with a subunit M(r) of 180,000. 6-Methylsalicyclic acid synthase also accepts acetoacetyl-CoA as an alternative starter molecule to acetyl-CoA. The enzyme also catalyses the formation of small amounts of triacetic acid lactone as an oligatory by-product of the reaction. In the absence of NADPH, triacetic acid lactone is the exclusive enzymic product, being formed at 10% of the rate of 6-methylsalicylic acid. The enzyme is inactivated by 1,3-dibromopropan-2-one, leading to the formation of cross-linked dimers similar to that observed with type I fatty acid synthases. Acetyl-CoA protects the enzyme against the inactivation and inhibits dimer formation. An adaptation of the purification method for 6-methylsalicylic acid synthase may be used for the isolation of fatty acid sythase from Penicillium patulum.
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20

Greenspan, M. D., H. G. Bull, J. B. Yudkovitz, D. P. Hanf, and A. W. Alberts. "Inhibition of 3-hydroxy-3-methylglutaryl-CoA synthase and cholesterol biosynthesis by β-lactone inhibitors and binding of these inhibitors to the enzyme." Biochemical Journal 289, no. 3 (February 1, 1993): 889–95. http://dx.doi.org/10.1042/bj2890889.

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The beta-lactones L-659,699 [(E,E)-11-[3-(hydroxymethyl)-4-oxo-2- oxetanyl]-3,5,7-trimethyl-2,4-undecadienoic acid) and its radioactive derivative 3H-L-668,411 (the 2,3-ditritiated methyl ester of L-659,699) inhibited a partially purified preparation of rat liver cytosolic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase with an IC50 of 0.1 microM. These compounds were also found to inhibit the incorporation of [14C]acetate into sterols in cultured Hep G2 cells with an IC50 of 3 microM. New kinetic evidence indicated that inhibition of the isolated enzyme was irreversible. In contrast, sterol biosynthesis in cultured Hep G2 cells was rapidly restored upon removal of the compound from the medium of inhibited cultures, suggesting reversibility of inhibition in the cells. Radioactivity was found to be associated with a single cytoplasmic protein by SDS/PAGE of the cytoplasm of Hep G2 cells after incubation of the cells with the inhibitor 3H-L-668,411. This protein was identified as cytoplasmic HMG-CoA synthase. Binding of the radioactive compound to the enzyme was decreased with time if the radioactive inhibitor was removed from the medium. Exposure of a gel containing the radioactive enzyme-inhibitor complex to neutral hydroxylamine also resulted in a loss of radioactivity from the gel. The purified rat liver enzyme reacted with the 3H-ligand to form a stable enzyme-inhibitor complex which could be isolated by h.p.l.c. Radioactivity was also subsequently lost from this complex when it was incubated with neutral hydroxylamine. Incorporation of [14C]acetate into cholesterol in mouse liver was inhibited in a reversible manner after oral administration of the beta-lactone inhibitor. These studies, as well as the kinetic evidence presented, suggest that the beta-lactone inhibitors acylate HMG-CoA synthase in a reaction which appears to be irreversible in vitro, but is easily reversed in cultured cells and in animals.
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Bestmann, Hans Jürgen, and Rainer Schobert. "Neue Synthese makrocyclischer Lactone." Angewandte Chemie 95, no. 10 (January 19, 2006): 810–11. http://dx.doi.org/10.1002/ange.19830951024.

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T. Mohd Ali, M., and . "Synthesis of -Hydroxy -Proline: Potential for Organocataly-sis Reactions." International Journal of Engineering & Technology 7, no. 4.14 (December 24, 2019): 237. http://dx.doi.org/10.14419/ijet.v7i4.14.27571.

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A chiral organic molecule, L-proline catalyzed an enantioselective transformation reaction has becoming interesting synthetic protocol especially in the area of organocatalysis. Herein, a synthetic approach towards -hydroxy--proline starting from bicyclic lactone lactam is hereby described. The syntheses utilized dicarboxylation reaction of bicyclic lacton lactam, followed by ether hydrolysis of the bicyclic ether and oxidation reaction of the primary alcohol. The synthetic strategy disclosed here allows further the enantioselective synthesis of a variety of unnatural amino acids based on -proline structure.
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Iida, Aya, Yasuo Ohnishi, and Sueharu Horinouchi. "Control of Acetic Acid Fermentation by Quorum Sensing via N-Acylhomoserine Lactones in Gluconacetobacter intermedius." Journal of Bacteriology 190, no. 7 (February 1, 2008): 2546–55. http://dx.doi.org/10.1128/jb.01698-07.

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ABSTRACT A number of gram-negative bacteria regulate gene expression in a cell density-dependent manner by quorum sensing via N-acylhomoserine lactones (AHLs). Gluconacetobacter intermedius NCI1051, a gram-negative acetic acid bacterium, produces three different AHLs, N-decanoyl-l-homoserine lactone, N-dodecanoyl-l-homoserine lactone, and an N-dodecanoyl-l-homoserine lactone with a single unsaturated bond in its acyl chain, as determined by liquid chromatography-tandem mass spectrometry. Two genes encoding an AHL synthase and a cognate regulator were cloned from strain NCI1051 and designated ginI and ginR, respectively. Disruption of ginI or ginR abolished AHL production, indicating that NCI1051 contains a single set of quorum-sensing genes. Transcriptional analysis showed that ginI is activated by GinR, which is consistent with the finding that there is an inverted repeat whose nucleotide sequence is similar to the sequence bound by members of the LuxR family at position −45 with respect to the transcriptional start site of ginI. A single gene, designated ginA, located just downstream of ginI is transcribed by read-through from the GinR-inducible ginI promoter. A ginA mutant, as well as the ginI and ginR mutants, grew more rapidly in medium containing 2% (vol/vol) ethanol and accumulated acetic acid at a higher rate with a greater final yield than parental strain NCI1051. In addition, these mutants produced larger amounts of gluconic acid than the parental strain. These data demonstrate that the GinI/GinR quorum-sensing system in G. intermedius controls the expression of ginA, which in turn represses oxidative fermentation, including acetic acid and gluconic acid fermentation.
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Canonne, P., and M. Akssira. "Synthèses stéréosélectives des γ-lactones bicycliques condensées." Tetrahedron 41, no. 18 (January 1985): 3695–704. http://dx.doi.org/10.1016/s0040-4020(01)91390-0.

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25

Meise, Werner, and Christoph Arth. "Synthese aromatisch anellierter ε-Lactone." Liebigs Annalen der Chemie 1992, no. 2 (February 12, 1992): 163–65. http://dx.doi.org/10.1002/jlac.199219920129.

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26

Latour, Xavier, St�phanie Diallo, Sylvie Chevalier, Dani�le Morin, Bruno Smadja, Jean-Fran�ois Burini, Dominique Haras, and Nicole Orange. "Thermoregulation of N-Acyl Homoserine Lactone-Based Quorum Sensing in the Soft Rot Bacterium Pectobacterium atrosepticum." Applied and Environmental Microbiology 73, no. 12 (April 27, 2007): 4078–81. http://dx.doi.org/10.1128/aem.02681-06.

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ABSTRACT The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level.
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27

Elasri, Miena, Sandrine Delorme, Philippe Lemanceau, Gordon Stewart, Bridget Laue, Eric Glickmann, Phil M. Oger, and Yves Dessaux. "Acyl-Homoserine Lactone Production Is More Common among Plant-Associated Pseudomonas spp. than among Soilborne Pseudomonas spp." Applied and Environmental Microbiology 67, no. 3 (March 1, 2001): 1198–209. http://dx.doi.org/10.1128/aem.67.3.1198-1209.2001.

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ABSTRACT A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL,N-hexanoyl-l-homoserine lactone,N-(3-oxo-hexanoyl)-homoserine lactone, andN-(3-oxo-octanoyl)-l-homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL could be found). Six strains of fluorescent pseudomonads, belonging to the species P. chlororaphis, P. fluorescens, and P. putida, isolated from the plant rhizosphere produced different types of NAHL. In contrast, none of the strains isolated from soil samples were shown to produce NAHL. The gene encoding the NAHL synthase in P. syringae pv. maculicola was isolated by complementation of an NAHL-deficient Chromobacteriummutant. Sequence analysis revealed the existence of aluxI homologue that we named psmI. This gene is sufficient to confer NAHL synthesis upon its bacterial host and has strong homology to psyI and ahlI, two genes involved in NAHL production in P. syringae pv. tabaci and P. syringae pv. syringae, respectively. We identified another open reading frame that we termedpsmR, transcribed convergently in relation topsmI and partly overlapping psmI; this gene encodes a putative LuxR regulatory protein. This gene organization, with luxI and luxRhomologues facing each other and overlapping, has been found so far only in the enteric bacteria Erwinia andPantoea and in the related species P. syringae pv. tabaci.
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Lehmann, Jochen, Khadiga M. Ghoneim, Bothaina Abd El-Fattah, and Adel A. Elgendy. "Lactone, 11. Mitt. Synthese von 4.9-Dihydropyrano[3.4-b]indol-1(3H)-onen aus α-Ethoxalyl-γ-lactonen." Archiv der Pharmazie 320, no. 1 (1987): 22–29. http://dx.doi.org/10.1002/ardp.19873200105.

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29

Teren, Martin, Hana Turonova Michova, Lucie Vondrakova, and Katerina Demnerova. "Molecules Autoinducer 2 and cjA and Their Impact on Gene Expression in Campylobacter jejuni." Journal of Molecular Microbiology and Biotechnology 28, no. 5 (2018): 207–15. http://dx.doi.org/10.1159/000495411.

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Quorum sensing is a widespread form of cell-to-cell communication, which is based on the production of signaling molecules known as autoinducers (AIs). The first group contains highly species-specific N-acyl homoserine lactones (N-AHLs), generally known as AI-1, which are produced by AHL synthase. The second group, possessing the characteristic structure of a furanone ring, are known as AI-2. The enzyme responsible for their production is S-ribosylhomocysteine lyase (LuxS). In <i>Campylobacter jejuni</i>, AI-2 and LuxS play a role in many important processes, including biofilm formation, stress response, motility, expression of virulence factors, and colonization. However, neither the receptor protein nor the exact structure of the AI-2 molecule have been identified to date. Similarly, little is known about the possible existence of AHL-synthase producing AI-1 and its impact on gene expression. Recently, an analogue of homoserine lactone, called cjA, was isolated from a cell-free supernatant of <i>C. jejuni</i> strain<i></i> 81–176 and from the food isolate c11. The molecule cjA particularly impacted the expression of virulence factors and biofilm formation. This review summarizes the role of AI-2 and cjA in the context of biofilm formation, motility, stress responses, and expression of virulence factors.
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Liu, Rai-Shung. "Synthesis of oxygen heterocycles via alkynyltungsten compounds." Pure and Applied Chemistry 73, no. 2 (January 1, 2001): 265–69. http://dx.doi.org/10.1351/pac200173020265.

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This short review article covers some useful applications of alkynyltungsten compounds to the syntheses of complex lactones. Two types of cyclizations will be emphasized: (1) cycloalkenylation of tungsten-alkynol compounds with aldehydes to give a-alkylidene oxacarbeniums, further leading to a-alkylidene lactones and (2) intramolecular [3+2]-cycloaddition of epoxides to give bicyclic lactones. The new methodologies can provide a short synthesis of enantiopure lactones such as (-) -epilitsenolide C2, (+) -listenolide C1, (+) -isodihydromahubanolide A, (+) -blastmycinone, and (-) -epi-blastmycinone.
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31

Liao, Lisheng, Amy L. Schaefer, Bruna G. Coutinho, Pamela J. B. Brown, and E. Peter Greenberg. "An aryl-homoserine lactone quorum-sensing signal produced by a dimorphic prosthecate bacterium." Proceedings of the National Academy of Sciences 115, no. 29 (July 2, 2018): 7587–92. http://dx.doi.org/10.1073/pnas.1808351115.

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Many species ofProteobacteriaproduce acyl-homoserine lactone (AHL) compounds as quorum-sensing (QS) signals for cell density-dependent gene regulation. Most known AHL synthases, LuxI-type enzymes, produce fatty AHLs, and the fatty acid moiety is derived from an acyl-acyl carrier protein (ACP) intermediate in fatty acid biosynthesis. Recently, a class of LuxI homologs has been shown to use CoA-linked aromatic or amino acid substrates for AHL synthesis. By using an informatics approach, we found the CoA class of LuxI homologs exists primarily in α-Proteobacteria. The genome ofProsthecomicrobium hirschii, a dimorphic prosthecate bacterium, possesses aluxI-like AHL synthase gene that we predicted to encode a CoA-utilizing enzyme. We show theP. hirschiiLuxI homolog catalyzes synthesis of phenylacetyl-homoserine lactone (PA-HSL). Our experiments showP. hirschiiobtains phenylacetate from its environment and uses a CoA ligase to produce the phenylacetyl-CoA substrate for the LuxI homolog. By using an AHL degrading enzyme, we showed that PA-HSL controls aggregation, biofilm formation, and pigment production inP. hirschii. These findings advance a limited understanding of the CoA-dependent AHL synthases. We describe how to identify putative members of the class, we describe a signal synthesized by using an environmental aromatic acid, and we identify phenotypes controlled by the aryl-HSL.
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Khider, Miriam, Hilde Hansen, Erik Hjerde, Jostein A. Johansen, and Nils Peder Willassen. "Exploring the transcriptome ofluxI−andΔainSmutants and the impact of N-3-oxo-hexanoyl-L- and N-3-hydroxy-decanoyl-L-homoserine lactones on biofilm formation inAliivibrio salmonicida." PeerJ 7 (April 30, 2019): e6845. http://dx.doi.org/10.7717/peerj.6845.

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BackgroundBacterial communication through quorum sensing (QS) systems has been reported to be important in coordinating several traits such as biofilm formation. InAliivibrio salmonicidatwo QS systems the LuxI/R and AinS/R, have been shown to be responsible for the production of eight acyl-homoserine lactones (AHLs) in a cell density dependent manner. We have previously demonstrated that inactivation of LitR, the master regulator of the QS system resulted in biofilm formation, similar to the biofilm formed by the AHL deficient mutantΔainSluxI−. In this study, we aimed to investigate the global gene expression patterns ofluxIandainSautoinducer synthases mutants using transcriptomic profiling. In addition, we examined the influence of the different AHLs on biofilm formation.ResultsThe transcriptome profiling ofΔainSandluxI−mutants allowed us to identify genes and gene clusters regulated by QS inA. salmonicida. Relative to the wild type, theΔainSandluxI−mutants revealed 29 and 500 differentially expressed genes (DEGs), respectively. The functional analysis demonstrated that the most pronounced DEGs were involved in bacterial motility and chemotaxis, exopolysaccharide production, and surface structures related to adhesion. Inactivation ofluxI, but notainSgenes resulted in wrinkled colony morphology. While inactivation of both genes (ΔainSluxI−) resulted in strains able to form wrinkled colonies and mushroom structured biofilm. Moreover, when theΔainSluxI−mutant was supplemented with N-3-oxo-hexanoyl-L-homoserine lactone (3OC6-HSL) or N-3-hydroxy-decanoyl-L-homoserine lactone (3OHC10-HSL), the biofilm did not develop. We also show that LuxI is needed for motility and for repression of EPS production, where repression of EPS is likely operated through the RpoQ-sigma factor.ConclusionThese findings imply that the LuxI and AinS autoinducer synthases play a critical role in the regulation of biofilm formation, EPS production, and motility.
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Yang, Menghua, Kejing Sun, Lei Zhou, Ruifu Yang, Zengtao Zhong, and Jun Zhu. "Functional analysis of three AHL autoinducer synthase genes in Mesorhizobium loti reveals the important role of quorum sensing in symbiotic nodulation." Canadian Journal of Microbiology 55, no. 2 (February 2009): 210–14. http://dx.doi.org/10.1139/w08-128.

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One of the most important signal transduction pathways in bacteria, quorum sensing, is involved in many regulatory circuits in rhizobia, especially in the control of communication between rhizobia and their plant hosts. In this study, we identified 3 autoinducer synthase genes — mrlI1, mrlI2, and mrlI3 — in Mesorhizobium loti NZP 2213. We found that MrlI1 and MrlI2 could synthesize distinct N-acyl homoserine lactone (AHL) autoinducers in rich medium cultures, and the expression of mrlI1 was shown to be growth-phase-dependent. MrlI3 did not produce any detectable AHL molecules under the culture conditions tested. To investigate whether these AHL synthases affect nodulation, we examined the nodulation of AHL-deficient mutants on their native plant host Lotus corniculatus and found that the efficiency of nodulation of bacteria with mutations of any of these 3 synthase genes was reduced, suggesting that quorum sensing systems in M. loti may play an important role in successful establishment of rhizobium–legume symbiosis.
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34

Kayser, Margaret M., Jun Zhu, and Donald L. Hooper. "On the synthesis and the mechanism of formation of halogenated enol lactones." Canadian Journal of Chemistry 75, no. 10 (October 1, 1997): 1322–30. http://dx.doi.org/10.1139/v97-158.

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The synthesis of halo enol lactones from cyclic anhydrides via lactonization of the corresponding keto phosphoranes provides a direct route to these interesting compounds, which possess important biological properties and are useful intermediates in organic synthesis. In this paper we outline the syntheses of several halo enol lactones and discuss mechanistic consequences of these reactions on the understanding of Wittig reactions with cyclic anhydrides. Keywords: halolactonization, cyclic anhydrides, halo enol lactones, Wittig reaction mechanism.
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35

Scott, Russell A., Jason Weil, Phuong T. Le, Paul Williams, Rupert G. Fray, Susanne B. von Bodman, and Michael A. Savka. "Long- and Short-Chain Plant-Produced Bacterial N-Acyl-Homoserine Lactones Become Components of Phyllosphere, Rhizosphere, and Soil." Molecular Plant-Microbe Interactions® 19, no. 3 (March 2006): 227–39. http://dx.doi.org/10.1094/mpmi-19-0227.

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Two N-acyl-homoserine lactone (acyl-HSL) synthase genes, lasI from Pseudomonas aeruginosa and yenI from Yersinia enterocolitica, were introduced into tobacco, individually and in combination. Liquid chromatograph-tandem mass spectrometry and thin-layer chromatography confirmed products of lasI and yenI activity in single and cotransformants. Cotransformants expressing plastid-localized LasI and YenI synthases produced the major acyl-HSLs for each synthase in all tissues tested. Total acyl-HSL signals accumulated in leaf tissue up to 3 pmol/mg of fresh weight, half as much in stem tissue, and approximately 10-fold less in root tissues. Acyl-HSLs were present in aqueous leaf washes from greenhouse-grown transgenic plants. Transgenic lines grown for 14 days under axenic conditions produced detectable levels of acyl-HSLs in root exudates. Ethyl acetate extractions of rhizosphere and nonrhizosphere soil from transgenically grown plants contained active acyl-HSLs, whereas plant-free soil or rhizosphere and nonrhizosphere soil from wild-type plants lacked detectable amounts of acyl-HSLs. This work shows that bioactive acyl-HSLs are exuded from leaves and roots and accumulate in the phytosphere of plants engineered to produce acyl-HSLs. These data further suggest that plants that are bioengineered to synthesize acyl-HSLs can foster beneficial plant-bacteria communications or deter deleterious interactions. Therefore, it is feasible to use bioengineered plants to supplement soils with specific acyl-HSLs to modulate bacterial phenotypes and plant-associated bacterial community structures.
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36

Tochtermann, Werner, and Fritjof Weidner. "Tetrahydrofurane und γ-Lactone, VII. Synthese und Reaktionen von γ,γ-disubstituierten γ-Lactonen – ein Weg zu funktionalisierten Dodecandisäure-Derivaten." Liebigs Annalen der Chemie 1994, no. 6 (June 13, 1994): 593–600. http://dx.doi.org/10.1002/jlac.199419940609.

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37

Altenbach, Hans-Josef, Winfried Holzapfel, Gerd Smerat, and Stefan H. Finkler. "Einfache, regiospezifische synthese von cycloalkenonen aus lactonen." Tetrahedron Letters 26, no. 51 (1985): 6329–32. http://dx.doi.org/10.1016/s0040-4039(01)84590-1.

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38

SUH, Dae-Yeon, Kazuki FUKUMA, Junichi KAGAMI, Yasuyo YAMAZAKI, Masaaki SHIBUYA, Yutaka EBIZUKA, and Ushio SANKAWA. "Identification of amino acid residues important in the cyclization reactions of chalcone and stilbene synthases." Biochemical Journal 350, no. 1 (August 9, 2000): 229–35. http://dx.doi.org/10.1042/bj3500229.

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Chalcone synthase (CHS) and stilbene synthase (STS) catalyse condensation reactions of p-coumaroyl-CoA and three C2 units from malonyl-CoA up to a common tetraketide intermediate but then catalyse different cyclization reactions to produce naringenin chalcone and resveratrol respectively. On the basis of sequence alignment with other condensing enzymes including 3-ketoacyl-(acyl carrier protein) synthases of polyketide and fatty-acid synthases, site-directed mutagenesis was performed on the active-site G372FGPG loops in CHS and STS. The CHS-P375G mutant showed a 6-fold decrease in overall condensing activity with selectively increased production of p-coumaroyltriacetic acid lactone (CTAL, the derailment product of the tetraketide intermediate). Meanwhile, resveratrol production by STS-P375G strongly decreased to give various products in the order CTAL > resveratrol≈ bisnoryangonin > naringenin. As a result, naringenin production (cross-reaction) by STS-P375G was close to 30% of resveratrol production. Both G374L mutants of CHS and STS showed no condensing activity with residual malonyl-CoA decarboxylase activity. These results suggested that the G372FGPG loop in CHS and STS contribute to a determination of the outcome during cyclization reactions by serving as a part of the active-site scaffold on which the stereochemistry of cyclization is performed. These observations provide the first biochemical indication that cyclization reactions are modulated by active-site geometry. The implications for the evolutionary relationship of these enzymes are also discussed.
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39

Lehmann, Jochen, and Thomas Rasche. "Lactone, 7. Mitt. Zur Synthese lactonverbrückter Diarylbutylamine." Archiv der Pharmazie 318, no. 8 (1985): 763–65. http://dx.doi.org/10.1002/ardp.19853180818.

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40

Lehmann, Jochen, and Axel Gossen. "Lactone, 14. Mitt.: Synthese lactonverbrückter 1,1-Diarylethylamine." Archiv der Pharmazie 320, no. 10 (October 1987): 1059–64. http://dx.doi.org/10.1002/ardp.198700009.

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Lehmann, Jochen, and Axel Gossen. "Lactone, 18. Mitt. Synthese lactonverbrückter 1,1-Diarylpropylamine." Archiv der Pharmazie 321, no. 8 (1988): 443–45. http://dx.doi.org/10.1002/ardp.19883210803.

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42

Göpfert, Jens, Anna-Katharina Bülow, and Otmar Spring. "Identification and Functional Characterization of a new Sunflower Germacrene A Synthase (HaGAS3)." Natural Product Communications 5, no. 5 (May 2010): 1934578X1000500. http://dx.doi.org/10.1177/1934578x1000500507.

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Sesquiterpenes and sesquiterpene lactones are major natural compounds found in linear and capitate glandular trichomes of sunflower, Helianthus annuus L. In addition to two recently identified germacrene A synthases HaGAS1 and HaGAS2, found in capitate trichome gland cells, reverse transcription-PCR experiments have now allowed identification of a third enzyme of this type, HaGAS3. Its cDNA sequence was established and its functional characterization as a germacrene A synthase was achieved through in vitro expression in engineered yeast, and by GC-MS experiments. PCR and RT-PCR experiments with cDNA from different plant organs revealed that the new enzyme is expressed independently from the other two. While these latter two were expressed in plant organs bearing capitate glandular trichomes and in roots, the new enzyme occurred in plant tissues not linked to the presence of specific trichomes (for example, cotyledons), and was absent in roots. The experiments show that independently regulated pathways for the first cyclic sesquiterpene, germacrene A, are present in sunflower.
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43

Kirwan, J. Paul, Ty A. Gould, Herbert P. Schweizer, Scott W. Bearden, Robert C. Murphy, and Mair E. A. Churchill. "Quorum-Sensing Signal Synthesis by the Yersinia pestis Acyl-Homoserine Lactone Synthase YspI." Journal of Bacteriology 188, no. 2 (January 15, 2006): 784–88. http://dx.doi.org/10.1128/jb.188.2.784-788.2006.

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ABSTRACT The acyl-homoserine lactone molecular species (AHLs) produced by the Yersinia pestis AHL synthase YspI were identified by biochemical and physical/chemical techniques. Bioassays of extracts from culture supernatants of the recombinant YspI and wild-type Yersinia pestis showed similar profiles of AHLs. Analysis by liquid chromatography-mass spectrometry revealed that the predominant AHLs were N-3-oxooctanoyl-l-homoserine lactone and N-3-oxo-hexanoyl-l-homoserine lactone.
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44

Hoang, Tung T., and Herbert P. Schweizer. "Characterization of Pseudomonas aeruginosa Enoyl-Acyl Carrier Protein Reductase (FabI): a Target for the Antimicrobial Triclosan and Its Role in Acylated Homoserine Lactone Synthesis." Journal of Bacteriology 181, no. 17 (September 1, 1999): 5489–97. http://dx.doi.org/10.1128/jb.181.17.5489-5497.1999.

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ABSTRACT The Pseudomonas aeruginosa fabI structural gene, encoding enoyl-acyl carrier protein (ACP) reductase, was cloned and sequenced. Nucleotide sequence analysis revealed that fabIis probably the last gene in a transcriptional unit that includes a gene encoding an ATP-binding protein of an ABC transporter of unknown function. The FabI protein was similar in size and primary sequence to other bacterial enoyl-ACP reductases, and it contained signature motifs for the FAD-dependent pyridine nucleotide reductase and glucose/ribitol dehydrogenase families, respectively. The chromosomal fabIgene was disrupted, and the resulting mutant was viable but possessed only 62% of the total enoyl-ACP reductase activity found in wild-type cell extracts. The fabI-encoded enoyl-ACP reductase activity was NADH dependent and inhibited by triclosan; the residual activity in the fabI mutant was also NADH dependent but not inhibited by triclosan. An polyhistidine-tagged FabI protein was purified and characterized. Purified FabI (i) could use NADH but not NADPH as a cofactor; (ii) used both crotonyl-coenzyme A and crotonyl-ACP as substrates, although it was sixfold more active with crotonyl-ACP; and (iii) was efficiently inhibited by low concentrations of triclosan. A FabI Gly95-to-Val active-site amino acid substitution was generated by site-directed mutagenesis, and the mutant protein was purified. The mutant FabI protein retained normal enoyl-ACP reductase activity but was highly triclosan resistant. When coupled to FabI, purified P. aeruginosa N-butyryl-l-homoserine lactone (C4-HSL) synthase, RhlI, could synthesize C4-HSL from crotonyl-ACP and S-adenosylmethionine. This reaction was NADH dependent and inhibited by triclosan. The levels of C4-HSL andN-(3-oxo)-dodecanoyl-l-homoserine lactones were reduced 50% in a fabI mutant, corroborating the role of FabI in acylated homoserine lactone synthesis in vivo.
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Li, Jian-Xu, Xin Fang, Qin Zhao, Ju-Xin Ruan, Chang-Qing Yang, Ling-Jian Wang, David J. Miller, et al. "Rational engineering of plasticity residues of sesquiterpene synthases from Artemisia annua: product specificity and catalytic efficiency." Biochemical Journal 451, no. 3 (April 12, 2013): 417–26. http://dx.doi.org/10.1042/bj20130041.

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Most TPSs (terpene synthases) contain plasticity residues that are responsible for diversified terpene products and functional evolution, which provide a potential for improving catalytic efficiency. Artemisinin, a sesquiterpene lactone from Artemisia annua L., is widely used for malaria treatment and progress has been made in engineering the production of artemisinin or its precursors. In the present paper, we report a new sesquiterpene synthase from A. annua, AaBOS (A. annua α-bisabolol synthase), which has high sequence identity with AaADS (A. annua amorpha-4,11-diene synthase), a key enzyme in artemisinin biosynthesis. Comparative analysis of the two enzymes by domain-swapping and structure-based mutagenesis led to the identification of several plasticity residues, whose alteration changed the product profile of AaBOS to include γ-humulene as the major product. To elucidate the underlying mechanisms, we solved the crystal structures of AaBOS and a γ-humulene-producing AaBOS mutant (termed AaBOS-M2). Among the plasticity residues, position 399, located in the substrate-binding pocket, is crucial for both enzymes. In AaBOS, substitution of threonine for leucine (AaBOSL339T) is required for γ-humulene production; whereas in AaADS, replacing the threonine residue with serine (AaADST399S) resulted in a substantial increase in the activity of amorpha-4,11-diene production, probably as a result of accelerated product release. The present study demonstrates that substitution of plasticity residues has potential for improving catalytic efficiency of the enzyme.
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46

Nguyen, Y. N., Haiqing Sheng, Rambabu Dakarapu, John R. Falck, Carolyn J. Hovde, and Vanessa Sperandio. "The Acyl-Homoserine Lactone Synthase YenI from Yersinia enterocolitica Modulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli O157:H7." Infection and Immunity 81, no. 11 (August 26, 2013): 4192–99. http://dx.doi.org/10.1128/iai.00889-13.

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ABSTRACTThe human pathogen enterohemorrhagicEscherichia coli(EHEC) O157:H7 colonizes the rectoanal junction (RAJ) in cattle, its natural reservoir. Colonization at the RAJ poses a serious risk for fecal shedding and contamination of the environment. We previously demonstrated that EHEC senses acyl-homoserine lactones (AHLs) produced by the microbiota in the rumen to activate thegadacid resistance genes necessary for survival through the acidic stomachs in cattle and to repress the locus of enterocyte effacement (LEE) genes important for colonization of the RAJ, but unnecessary in the rumen. Devoid of AHLs, the RAJ is the prominent site of colonization of EHEC in cattle. To determine if the presence of AHLs in the RAJ could repress colonization at this site, we engineered EHEC to express theYersinia enterocoliticaAHL synthase geneyenI, which constitutively produces AHLs, to mimic a constant exposure of AHLs in the environment. TheyenI+EHEC produces oxo-C6-homoserine lactone (oxo-C6-HSL) and had a significant reduction in LEE expression, effector protein secretion, and attaching and effacing (A/E) lesion formationin vitrocompared to the wild type (WT). TheyenI+EHEC also activated expression of thegadgenes. To assess whether AHL production, which decreases LEE expression, would decrease RAJ colonization by EHEC, cattle were challenged at the RAJ with WT oryenI+EHEC. Although theyenI+EHEC colonized the RAJ with efficiency equal to that of the WT, there was a trend for the cattle to shed the WT strain longer than theyenI+EHEC.
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47

Ulrich, Ricky L., Harry B. Hines, N. Parthasarathy, and Jeffrey A. Jeddeloh. "Mutational Analysis and Biochemical Characterization of the Burkholderia thailandensis DW503 Quorum-Sensing Network." Journal of Bacteriology 186, no. 13 (July 1, 2004): 4350–60. http://dx.doi.org/10.1128/jb.186.13.4350-4360.2004.

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ABSTRACT Numerous gram-negative bacteria communicate and regulate gene expression through a cell density-responsive mechanism termed quorum sensing (QS), which involves the synthesis and perception of diffusible N-acyl-homoserine lactones (AHL). In this study we genetically and physiologically characterized the Burkholderia thailandensis DW503 QS network. In silico analysis of the B. thailandensis genome revealed the presence of at least three AHL synthases (AHS) and five transcriptional regulators belonging to the LuxIR family of proteins. Mass spectrometry demonstrated that wild-type B. thailandensis synthesizes N-hexanoyl-homoserine lactone (C6-HSL), N-octanoyl-homoserine lactone (C8-HSL), and N-decanoyl-homoserine lactone (C10-HSL). Mutation of the btaI1 (luxI) AHS gene prevented accumulation of C8-HSL in culture supernatants, enhanced beta-hemolysis of sheep erythrocytes, increased lipase production, and altered colony morphology on swarming and twitching motility plates. Disruption of the btaI3 (luxI) AHS prevented biosynthesis of C6-HSL and increased lipase production and beta-hemolysis, whereas mutagenesis of the btaI2 (luxI) allele eliminated C10-HSL accumulation and reduced lipase production. Complementation of the btaI1 and btaI3 mutants fully restored the synthesis of C8-HSL and C6-HSL to parental levels. In contrast, mutagenesis of the btaR1, btaR3, btaR4, and btaR5 (luxR) transcriptional regulators had no effect on AHL accumulation, enhanced lipase production, and resulted in extensive beta-hemolysis on sheep blood agar plates. Furthermore, interruption of the btaI1, btaR1, and btaR3 genes altered colony morphology on twitching and swarming motility plates and induced pigmentation. Additionally, phenotypic microarray analysis indicated that QS in B. thailandensis both positively and negatively affects the metabolism of numerous substrates, including citric acid, formic acid, glucose 6-phosphate, capric acid, γ-hydroxybutyric acid, and d-arabinose. These results demonstrate that mutagenesis of the B. thailandensis QS system affects various cellular processes, including lipase production, swarming and twitching motility, beta-hemolysis of sheep erythrocytes, and carbon metabolism and/or transport.
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48

Dirat, O., C. Kouklovsky, M. Mauduit, and Y. Langlois. "Oxazoline-N-oxide mediated asymmetric cycloadditions. Recent progress in the stereo-selective syntheses of β-lactones and β-lactams." Pure and Applied Chemistry 72, no. 9 (January 1, 2000): 1721–37. http://dx.doi.org/10.1351/pac200072091721.

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Camphor-derived oxazoline-N-oxides are versatile dipoles in a new kind of asymmetric [2+3] cycloadditions. Recent applications of this methodology allowed the stereoselective syntheses of several b-lactones natural products such as 1233A and tetrahydrolipstatine. Two formal syntheses of b-lactams antibiotics, b-methyl thienamycin and carpetimycin A, have also been achieved using this type of cycloaddition.
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49

Marco, J. Alberto, and Miguel Carda. "Stereoselective Synthesis of Five Biologically Active, Naturally Occurring Medium and Large Ring Lactones." Natural Product Communications 6, no. 4 (April 2011): 1934578X1100600. http://dx.doi.org/10.1177/1934578x1100600411.

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Stereoselective syntheses of five naturally occurring, pharmacologically active medium and large ring lactones are described. Key synthetic methods used were, depending on the cases, olefin metatheses, asymmetric allylations and C-glycosidations.
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50

Molina, Lázaro, Fabio Rezzonico, Geneviève Défago, and Brion Duffy. "Autoinduction in Erwinia amylovora: Evidence of an Acyl-Homoserine Lactone Signal in the Fire Blight Pathogen." Journal of Bacteriology 187, no. 9 (May 1, 2005): 3206–13. http://dx.doi.org/10.1128/jb.187.9.3206-3213.2005.

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ABSTRACT Erwinia amylovora causes fire blight disease of apple, pear, and other members of the Rosaceae. Here we present the first evidence for autoinduction in E. amylovora and a role for an N-acyl-homoserine lactone (AHL)-type signal. Two major plant virulence traits, production of extracellular polysaccharides (amylovoran and levan) and tolerance to free oxygen radicals, were controlled in a bacterial-cell-density-dependent manner. Two standard autoinducer biosensors, Agrobacterium tumefaciens NTL4 and Vibrio harveyi BB886, detected AHL in stationary-phase cultures of E. amylovora. A putative AHL synthase gene, eamI, was partially sequenced, which revealed homology with autoinducer genes from other bacterial pathogens (e.g., carI, esaI, expI, hsII, yenI, and luxI). E. amylovora was also found to carry eamR, a convergently transcribed gene with homology to luxR AHL activator genes in pathogens such as Erwinia carotovora. Heterologous expression of the Bacillus sp. strain A24 acyl-homoserine lactonase gene aiiA in E. amylovora abolished induction of AHL biosensors, impaired extracellular polysaccharide production and tolerance to hydrogen peroxide, and reduced virulence on apple leaves.
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