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Functional Characterization of a New Antarctic Microbial Esterase EST112-2 and Its Use in the Preparation of Chiral Tertiary Alcohol (S)-Linalool
No full textChiral tertiary alcohols (TAs) are key building blocks for the synthesis of many crucial flavor compounds and pharmaceuticals. The two enantiomers of tertiary alcohol, linalool, differ in odor. So, sustainable strategies for the manufacture of optically pure TAs represented by linalool, are highly desirable. But the enzymatic synthesis of chiral tertian' alcohols through kinetic resolution was not easily achieved, possibly because of the steric hindrance from the chemical structures of tertiary alcohols. Herein, we identified and functionally characterized a new microbial esterase EST112-2 from the antarctic sediments and utilized esterase EST112-2 as a green biocatalyst in the synthesis of chiral tertiary alcohol (S)-linalool through asymmetric hydrolysis of racemic linalyl acetate. Parameters such as pH, temperature, co-solvents, substrate concentrations, enzyme loading and reaction time were optimized for the kinetic resolutions. Desired chiral product (S)-linalool was finally obtained with an enantiomeric excess of over 66% and a yield of over 72% after process optimization. The enantiomeric excess of (S)-linalool prepared by esterase EST112-2 was much higher than that from previous reports
Bioactive Pyridone Alkaloids from a Deep-Sea-Derived Fungus Arthrinium sp UJNMF0008
No full textEight new 4-hydroxy-2-pyridone alkaloids arthpyrones D-K (1-8), along with two known analogues apiosporamide (9) and arthpyrone B (10), were isolated from a deep-sea-derived fungus Arthrinium sp. UJNMF0008. The structures of the isolated compounds were elucidated on the basis of spectroscopic methods with that of 1 being established by chemical transformation and X-ray diffraction analysis. Compounds 1 and 2 bore an ester functionality linking the pyridone and decalin moieties first reported in this class of metabolites, while 3 and 4 incorporated a rare natural hexa- or tetrahydrobenzofuro[3,2-c]pyridin-3(2H)-one motif. Compounds 3-6 and 9 exhibited moderate to significant antibacterial activity against Mycobacterium smegmatis and Staphylococcus aureus with IC50 values ranging from 1.66-42.8 M, while 9 displayed cytotoxicity against two human osteosarcoma cell lines (U2OS and MG63) with IC50 values of 19.3 and 11.7 M, respectively
Cytotoxic Anthracycline Metabolites from a Recombinant Streptomyces
No full textThe C7 (C9 or C10)-O-L-rhodosamine-bearing anthracydine antibiotic cytorhodins and their biosynthetic intermediates were recently isolated from Streptomyces sp. SCSIO 1666. Cosmid p17C4 from the Streptomyces lydicus genomic library, which harbors both the biosynthetic genes for L-rhodinose (or 2-deoxy-L-fucose) and its glycosyltransferase (encoded by slgG), was introduced into SCSIO 1666 to yield the recombinant strain Streptomyces sp. SCSIO 1666/17C4. Chemical investigations of this strain's secondary metabolic potential revealed the production of different anthracyclines featuring C7-O-L-rhodinose (or 2-deoxy-L-fucose) instead of the typically observed L-rhodosamine. Purification of the fermentation broth yielded 12 new anthracycline antibiotics including three new epsilon-rhodomycinone derivatives, 1, 4, and 8, nine new beta-rhodomycinone derivatives, 2, 3, 5-7, and 9-12, three known compounds, L-rhodinose-L-rhodinose-L-rhodinoserhodomycinone (13), e-rhodomycinone (14), and gamma-rhodomycinone (15). All compounds were characterized on the basis of detailed spectroscopic analyses and comparisons with previously reported data. These compounds exhibited cytotoxicity against a panel of human cancer cell lines. Significantly, compounds 4 and 13 displayed pronounced activity against HCT-116 as characterized by IC50 values of 0.3 and 0.2 mu M, respectively; these IC50 values are comparable to that of the positive control epirubicin
Planaxidae (Mollusca, Gastropoda) from the South China Sea
No full textPlanaxidae is a family of tropical and subtropical marine gastropods that are adapted to an intertidal, rocky environment. The present study deals with three species in the family Planaxidae from the South China Sea: Planaxis sulcatus (von Born, 1778), Angiola longispira (Smith, 1872), and Supplanaxis niger (Quoy and Gaimard, 1833), based on specimens deposited in the Marine Biodiversity Collections of the South China Sea, Chinese Academy of Sciences. The taxonomic status, main morphological characteristics of the shell and radula, distribution, and habitat of these three planaxid species are presented. We also briefly discuss their morphological differences and the biogeographic distribution
Enzymatic Synthesis of GDP-alpha-L-fucofuranose by MtdL and Hyg20
No full textTwo mutases, MtdL and Hyg20, are reported. Both are able to functionally drive the biosynthesis of GDP-alpha-L-fucofuranose. Both enzymes catalyze similar functions, catalytically enabling the bidirectional reaction between GDP-beta-L-fucopyranose and GDP-alpha-L-fucofuranose using only divalent cations as cofactors. This realization is but one of a number of important insights into fucofuranose biosynthesis presented herein
Establishment and characterization of a brain-cell line from kelp grouper Epinephelus moara
No full textA new brain-cell line, EMB, was developed from kelp grouper Epinephelus moara, a cultured marine fish. The EMB cells were subcultured for more than 60 passages. The cells were cultured in Leibovitz's L-15 medium (L15) supplemented with antibiotics, foetal bovine serum (FBS), 2-mercaptoethanol (2-ME) and basic fibroblast growth factor (bFGF). The cells could grow at 18-30 degrees C, with the maximum growth between 24 and 30 degrees C. The optimum FBS concentration for the cells growth ranged between 15 and 20%. Chromosome analysis indicated that the modal chromosome number was 48 in the cells at passage 45. After being transfected with pEGFP-N3 plasmid, the cells could successfully express green fluorescence protein (GFP), implying that this cell line can be used for transgenic studies. A significant cytopathic effect (CPE) was observed in the cells after infection with Singapore grouper iridovirus (SGIV) or red spotted grouper nervous necrosis virus (RGNNV) and the viral replication was confirmed by quantitative real-time PCR (qrt-PCR) assay, which suggested EMB's application potential for studies of SGIV and RGNNV
Tumor necrosis factor receptor-associated factor 3 from Anodonta woodiana is an important factor in bivalve immune response to pathogen infection
No full textTumor necrosis factor receptor-associated factor 3 (TRAF3) is a multifunctional adaptor protein in innate and acquired immune system that plays a key role in the regulation of the RIG-I-like receptor (RLR) and Toll-like receptor (TLR) signaling pathway in mammals. However, the immune function of TRAF3 homologs in freshwater mollusks is not well understood. In this study, we identified a bivalve TRAF3 gene (AwTRAF3) from Anodonta woodiana and investigated its potential roles during immune challenges. The present AwTRAF3 encoded a polypeptide of 562 amino acids with predicted molecular mass of 64.5 kDa and PI of 7.9. Similar to other reported TRAF3s, AwTRAF3 contained a RING finger domain, two TRAF domains with zinc finger domains, a coiled coil region and a conserved C-terminal meprin and TRAF homology (MATH) domain. Quantitative real-time PCR (qRT-PCR) analysis revealed that AwTRAF3 mRNA was broadly expressed in all of the examined tissues, with high expression in hepatopancreas, gill and heart. In addition, immune challenge experiments directly showed that transcript levels of AwTRAF3 in hepatopancreas were significantly regulated upon bacterial (Vibrio alginolyticus and Staphylococcus aureus) and viral (poly (I:C)) challenges, respectively. Moreover, GFP-tagged AwTRAF3 fusion protein was found to be located primarily in the cytoplasm in HEK293T cells. Altogether, these data provided the first experimental demonstration that freshwater mollusks possess a functional TRAF3 that was involved in the innate defense against bacterial and viral infection
Tandem Hydration of Diisonitriles Triggered by Isonitrile Hydratase in Streptomyces thioluteus
No full textThe biosynthetic pathway of diisonitrile chalkophore SF2768 was identified in Streptomyces thioluteus through heterologous expression recently. Isolation and structure elucidation of the N-substituted formamides that coexisted with the diisonitriles implied that a hydration event was involved. In vitro enzymatic assays of an endogenous isonitrile hydratase suggested a rare sequential-hydration of the diisonitriles. Additionally, the results of Cu-CAS assays indicate that both partial and complete hydration led to the loss of the copper-chelating ability of SF2768
Observed Cross-Shelf Flow Induced by Mesoscale Eddies in the Northern South China Sea
No full textCross-shelf flow induced by mesoscale eddies has been investigated in the northern South China Sea (NSCS) using velocity observations from Long Ranger ADCP moorings. Mesoscale eddies influenced the three mooring stations during almost all the observation period. Four quadrants have been defined with the mooring location as the origin, and it is found that warm (cold) mesoscale eddies induce onshore (offshore) movement in the eastern two quadrants and offshore (onshore) movement in the western two quadrants. When an eddy propagates past a mooring station, net cross-shelf flow at the mooring station can be induced by asymmetry in the horizontal and vertical structure of the eddy and by its evolution. As an eddy propagates westward, its shape changes continually and the vertical modes also transform from high to lower modes, which contributes to the net cross-shelf flow. Based on the quasigeostrophic potential vorticity equation, it is confirmed that the net cross-shelf flow is mainly induced by the eddy evolution and suppressed by nonlinear effect. Because of dispersion characteristics of the mesoscale eddy, barotropic mode will restructure at the baroclinic mode area after separating from the baroclinic mode, which will be enhanced by topography slope
Indo-Pacific climate during the decaying phase of the 2015/16 El Nio: role of southeast tropical Indian Ocean warming
No full textThis study investigates the influence of southeast tropical Indian Ocean (SETIO) sea surface temperature (SST) warming on Indo-Pacific climate during the decaying phase of the 2015/16 El Nio by using observations and model experiments. The results show that the SETIO SST warming in spring 2016 enhanced local convection and forced a "C-shape" wind anomaly pattern in the lower troposphere. The "C-shape" wind anomaly pattern over the eastern tropical Indian Ocean consists of anomalous westerly flow south of the equator and anomalous easterly flow north of the equator. The anomalous easterly flow then extended eastward into the western North Pacific (WNP) and facilitates the development or the maintenance of an anomalous anticyclone over the South China Sea (SCS). Correspondingly, the eastern part of the Bay of Bengal, the SCS and the WNP suffered less rainfall. Such precipitation features and the associated "C-shape" wind anomaly pattern shifted northward about five latitudes in summer 2016. Additionally, the SETIO warming can induce local meridional circulation anomalies, which directly affect Indo-Pacific climate. Numerical model experiments further confirm that the SETIO SST warming plays an important role in modulating Indo-Pacific climate