Ah Reum Han

Ewha Womans University, Sŏul, Seoul, South Korea

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Publications (36)109.57 Total impact

  • AR Han · U Kang · YS Kil · EK Seo ·

    Planta Medica 06/2015; 81(11). DOI:10.1055/s-0035-1556534 · 2.15 Impact Factor
  • Yun‐Seo Kil · Ah‐Reum Han · Eun Kyoung Seo ·

    ChemInform 01/2015; 46(2). DOI:10.1002/chin.201502194
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    ABSTRACT: Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition in a temperate forest. Using the litterbag method, the decomposition rate and nitrogen, phosphorous, and carbon dynamics of Mongolian oak (Quercus mongolica), Korean pine (Pinus koraiensis), and their mixed leaf litter were compared for 24 months in a Mongolian oak stand, an adjacent Korean pine plantation, and a Mongolian oakKorean pine mixed stand. The decomposition rates of all the leaf litter types followed a pattern of distinct seasonal changes: most leaf litter decomposition occurred during the summer. Tree species was less influential on the leaf litter decomposition. The decomposition rates among different leaf litter types within the same stand were not significantly different, indicating no mixed litter effect. The immobilization of leaf litter N and P lasted for 14 months. Mongolian oak leaf litter and Korean pine leaf litter showed different N and P contents and dynamics during the decomposition, and soil P2O5 was highest in the Korean pine plantation, suggesting effects of plantation on soil nutrient budget.
    Forests 10/2014; 5(10):2561-2580. DOI:10.3390/f5102561 · 1.45 Impact Factor
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    Yun Seo Kil · Ah- Reum Han · Eun Kyoung Seo ·

    Bulletin of the Korean Chemical Society 06/2014; 35(6). DOI:10.5012/bkcs.2014.35.6.1891 · 0.80 Impact Factor
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    ABSTRACT: isolation and structure elucidation
    ChemInform 02/2014; 45(8). DOI:10.1002/chin.201408224
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    ABSTRACT: The main function of methionine sulfoxide reductases (Msr) in many organisms is to protect cells against oxidative stress caused by the catalyzed reduction of oxidized methionine to normal methionine. In a few micro-organisms, the existence of Msr as a fusion protein on a single polypeptide, MsrAB, was reported. However, Msr generally exists as separate enzymes MsrA and MsrB. Here, MsrAB from Helicobacter pylori (HpMsrAB) was overexpressed in Escherichia coli, purified, and crystallized to determine its structure. HpMsrAB X-ray diffraction data were collected to the resolution of 3.3 Å, and the crystals were found to belong to the tetragonal space group P41212, with the unit cell parameters a =100.91, b =100.91, and c =160.08 Å. The crystals corresponded to 5.38 Å3 Da−1 of Matthews coefficient and 77.2% solvent content from the molecular replacement suggest that there is a single molecule in an asymmetric unit. Due to their unusually high solvent content, diffraction of these crystals only reach a resolution of 3.3 Å. A preliminary solution was determined by molecular replacement. Further refinement of the structure is in progress.
    Journal of the Korean Society for Applied Biological Chemistry 02/2014; 57(1):23-26. DOI:10.1007/s13765-013-4183-5 · 0.69 Impact Factor
  • Mun Ock Kim · Sun Hwa Lee · Jee Hee Seo · Il Soon Kim · Ah Reum Han · Dong Oh Moon · Sungchan Cho · Long Cui · Jungwoo Kim · Hyun Sun Lee ·
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    ABSTRACT: Abstract Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first committed step in triacylglycerol (TAG) and phospholipid biosynthesis, and has been considered as one of the drug targets for treating hepatic steatosis, insulin resistance, and other metabolic disorders. The aim of this study was to investigate the GPAT inhibitors from natural products and to evaluate their effects. The methanol extract of Aralia cordata roots showed a strong inhibitory effect on the human GPAT1 activity. A further bioactivity-guided approach led to the isolation of ent-pimara-8(14),15-dien-19-oic acid, (PA), one of the major compounds of A. cordata, which suppressed the GPAT1 activity with IC50 value of 60.5 μM. PA markedly reduced de novo lysophosphatidic acid synthesis through inhibition of GPAT activity and therefore significantly decreased synthesis of TAG in the HepG2 cells. These results suggest that PA as well as A. cordata root extract could be beneficial in controlling lipid metabolism.
    Journal of medicinal food 11/2013; 16(12). DOI:10.1089/jmf.2012.2636 · 1.63 Impact Factor
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    ABSTRACT: Expression plasmids carrying different deoxysugar biosynthetic gene cassettes and the gene encoding a substrate-flexible glycosyltransferase DesVII were constructed and introduced into Streptomyces venezuelae YJ003 mutant strain bearing a deletion of a desosamine biosynthetic (des) gene cluster. The resulting recombinants produced macrolide antibiotic YC-17 analogues possessing unnatural sugars replacing native D-desosamine. These metabolites were isolated and further purified using chromatographic techniques and their structures were determined as D-quinovosyl-10-deoxymethynolide, L-rhamnosyl-10-deoxymethynolide, L-olivosyl-10-deoxymethynolide, and D-boivinosyl-10-deoxymethynolide on the basis of 1D and 2D NMR and MS analyses and the stereochemistry of sugars was confirmed using coupling constant values and NOE correlations. Their antibacterial activities were evaluated in vitro against erythromycin-susceptible and -resistant Enterococcus faecium and Staphylococcus aureus. Substitution with L-rhamnose displayed better antibacterial activity than parent compound YC-17 containing native sugar D-desosamine. The present study on relationships between chemical structures and antibacterial activities could be useful in generation of novel advanced antibiotics utilizing combinatorial biosynthesis approach.
    Journal of Biotechnology 06/2013; 168(2). DOI:10.1016/j.jbiotec.2013.05.014 · 2.87 Impact Factor
  • Ah Reum Han · Sun Kyung Lee · Gang Uk Suh · Yunmi Park · Pil Sun Park ·
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    ABSTRACT: Tree growth in subalpine ecosystems is sensitive to wind due to their wide exposure to strong winds and sparsely wooded short surroundings. This study was conducted to understand the effects of wind and topographic wind barriers on the tree growth in a subalpine ecosystem. The annual shoot growth, bud mortality and needle moisture content of Jezo spruce (Picea jezoensis (Siebold et Zucc.) Carrière) were compared between a wind-exposed site and a wind-protected site. The wind-exposed site was located in a windward position and was exposed directly to the prevailing winds from W and WSW. The wind-protected site was located on leeward slopes with topographic barriers that blocked the prevailing winds. The wind-exposed site had higher air temperature, lower soil water content and shallower snow depth than the wind-protected site in late winter and spring. The annual mean shoot growth on the wind-exposed site was 4 cm – significantly lower than that of 6.1 cm on the wind-protected site (P < 0.01). The bud mortality was highest at 32.9% in the western sectors of the upper crowns in the wind-exposed site, which was the crown sector that was most exposed to the prevailing winds. The needle moisture content decreased by 8–60% from January 2009 to April 2009, and the decrease was significantly higher in the wind-exposed site than in the wind-protected site (P < 0.01), indicating the potential for drought stress in trees in the wind-exposed site. Topographic wind barriers play a decisive role on the tree growth in subalpine areas by changing temperature and moisture regimes, lowering needle moisture loss and bud mortality, and reducing the potential for drought stress.
    Agricultural and Forest Meteorology 12/2012; s 166–167:207–214. DOI:10.1016/j.agrformet.2012.07.017 · 3.76 Impact Factor
  • UJ Youn · YS Kil · U Kang · YJ Lee · HJ Shin · JW Nam · AR Han · SH Sung · J Kim · SM Lee · D Lee · JH Lee · EK Seo ·

    Planta Medica 07/2012; 78(11). DOI:10.1055/s-0032-1320862 · 2.15 Impact Factor
  • Shree Prasad Thapa · Ah Reum Han · Jun Mo Cho · Jang Hyun Hur ·
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    ABSTRACT: A multiplex PCR and DNA array for quick detection of Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. was developed using specific genetic markers derived from virulence-related genes. The genetic markers of cytK, sei, prfA, rfB, and hilA gene specifically amplified DNA fragments of 320 bp, 500 bp, 700 bp, 1.0 kb and 1.2 kb from B. cereus, S. aureus, L. monocytogenes, E. coli O157:H7, and Salmonella spp., respectively. These markers are specific for the detection of the corresponding target pathogens. The sensitivity of the genetic markers was down to ∼0.5 fg genomic DNA and ∼101 CFU/ml (one bacterial cell per reaction) of bacterial culture. The combination of mPCR and DNA macroarray hybridization sensitively and specifically detected B. cereus, S. aureus, L. monocytogenes, E. coli O157:H7, and Salmonella spp., in complex mixed cultures and food matrices. Thus, this mPCR and macroarray-based approach serves as rapid and reliable diagnostic tool for the detection of these five pathogens.
    Annals of Microbiology 06/2012; 63(2). DOI:10.1007/s13213-012-0526-4 · 0.99 Impact Factor
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    ABSTRACT: Methionine sulfoxide reductase (Msr) is a repair enzyme that reduces oxidized methionine to methionine. The Msr enzyme is divided into MsrA and MsrB, which reduce the S and R configurations of the substrate, respectively. In some pathogenic bacteria MsrA and MsrB exist in a fusion-protein form, MsrAB. In this study, the recombinant MsrA part of MsrAB from Haemophilus influenzae (HIMsrA) was overexpressed, purified and crystallized using the hanging-drop vapour-diffusion method. A diffraction data set was collected to 1.6 Å resolution. The crystal of HIMsrA was found to belong to space group P4(1)2(1)2, with unit-cell parameters a = b = 57.29, c = 186.28 Å, a calculated Matthews coefficient of 1.82 Å(3) Da(-1) and two molecules per asymmetric unit. A preliminary solution was determined by molecular replacement. Refinement of the structure is currently in progress.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 05/2012; 68(Pt 5):557-9. DOI:10.1107/S1744309112011256 · 0.53 Impact Factor
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    ABSTRACT: Three new flavonoids, 5,6,7,8,3′,4′-hexamethoxyhomoflavone (1), 5,6,7,8,4′-pentamethoxyhomoflavone (2) and 3,6,7,8,2′,5′-hexamethoxyflavone (3) were isolated from the peels of mature fruits of Citrus unshiuMarcow (Rutaceae), together with the three known compounds 6,7,8,4′-tetramethoxyflavone (=6,7,8-trimethoxy-2-(4-methoxyphenyl)-4H-1-benzopyran-4-one), 3,5,7,8,2′,5′-hexamethoxyflavone (=2-(2,5-dimethoxyphenyl)-3,5,7,8-tetramethoxy-4H-1-benzopyran-4-one), and scopoletin (=7-hydroxy-6-methoxy-2H-1-benzopyran-2-one) of which the former two have never been isolated from natural resources, although they have been reported as synthetic compounds. The structures of 1–3 were elucidated on the basis of spectroscopic evidence, including 1D- and 2D-NMR analysis.
    Helvetica Chimica Acta 02/2012; 95(2). DOI:10.1002/hlca.201100286 · 1.14 Impact Factor
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    ABSTRACT: The adult and the early stages of Cydia piceicola, sp. nov., are described and illustrated from Korea. Larvae of the new species feed on Picea jezoensis (Siebold et Zucc.) Carrière, The life history and larval feeding habits are briefly discussed.
    Entomological Research 11/2011; 41(6). DOI:10.1111/j.1748-5967.2011.00350.x · 0.40 Impact Factor
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    ABSTRACT: Kanamycin is one of the most widely used antibiotics, yet its biosynthetic pathway remains unclear. Current proposals suggest that the kanamycin biosynthetic products are linearly related via single enzymatic transformations. To explore this system, we have reconstructed the entire biosynthetic pathway through the heterologous expression of combinations of putative biosynthetic genes from Streptomyces kanamyceticus in the non-aminoglycoside-producing Streptomyces venezuelae. Unexpectedly, we discovered that the biosynthetic pathway contains an early branch point, governed by the substrate promiscuity of a glycosyltransferase, that leads to the formation of two parallel pathways in which early intermediates are further modified. Glycosyltransferase exchange can alter flux through these two parallel pathways, and the addition of other biosynthetic enzymes can be used to synthesize known and new highly active antibiotics. These results complete our understanding of kanamycin biosynthesis and demonstrate the potential of pathway engineering for direct in vivo production of clinically useful antibiotics and more robust aminoglycosides.
    Nature Chemical Biology 11/2011; 7(11):843-52. DOI:10.1038/nchembio.671 · 13.00 Impact Factor
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    ABSTRACT: Metabolic engineering of plant-specific phenylpropanoid biosynthesis has attracted an increasing amount of attention recently, owing to the vast potential of flavonoids as nutraceuticals and pharmaceuticals. Recently, we have developed a recombinant Streptomyces venezuelae as a heterologous host for the production of flavonoids. In this study, we successfully improved flavonoid production by expressing two sets of genes predicted to be involved in malonate assimilation. The introduction of matB and matC encoding for malonyl-CoA synthetase and the putative dicarboxylate carrier protein, respectively, from Streptomyces coelicolor into the recombinant S. venezuelae strains expressing flavanone and flavone biosynthetic genes resulted in enhanced production of both flavonoids.
    Journal of Microbiology and Biotechnology 11/2011; 21(11):1143-6. · 1.53 Impact Factor
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    ABSTRACT: A 14-membered macrolide antibiotic narbomycin produced from Streptomyces venezuelae ATCC 15439 is composed of polyketide macrolactone ring and D-desosamine as a deoxysugar moiety, which acts as an important determinant of its antibacterial activity. In order to generate diverse glycosylated derivatives of narbomycin, expression plasmids carrying different deoxysugar biosynthetic gene cassettes and the gene encoding a substrate-flexible glycosyltransferase DesVII were constructed and introduced into S. venezuelae YJ003 mutant strain bearing a deletion of thymidine-5'-diphospho-D-desosamine biosynthetic gene cluster. The resulting recombinants of S. venezuelae produced a range of new analogs of narbomycin, which possess unnatural sugar moieties instead of native deoxysugar D-desosamine. The structures of narbomycin derivatives were determined through nuclear magnetic resonance spectroscopy and mass spectrometry analyses and their antibacterial activities were evaluated in vitro against erythromycin-susceptible and -resistant Enterococcus faecium and Staphylococcus aureus. Substitution with L-rhamnose or 3-O-demethyl-D-chalcose was demonstrated to exhibit greater antibacterial activity than narbomycin and the clinically relevant erythromycin. This work provides new insight into the functions of deoxysugar biosynthetic enzymes and structure-activity relationships of the sugar moieties attached to the macrolides and demonstrate the potential of combinatorial biosynthesis for the generation of new macrolides carrying diverse sugars with increased antibacterial activities.
    Applied Microbiology and Biotechnology 09/2011; 93(3):1147-56. DOI:10.1007/s00253-011-3592-9 · 3.34 Impact Factor
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    ABSTRACT: Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as-prepared manganese oxide–aluminum oxide nanocomposite is X-ray amorphous whereas heat-treatment gives rise to the crystallization of an α-MnO2 phase at 600 °C and Mn3O4/Mn2O3 and γ-Al2O3 phases at 800 °C. Electron microscopy and N2 adsorption-desorption-isotherm analysis clearly demonstrate that the as-prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ∼20 nm and a surface area of >410 m2 g−1. Of particular interest is that the small particle size of the as-prepared nanocomposite is well-maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very-high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals.
    Advanced Functional Materials 06/2011; 21(12):2301 - 2310. DOI:10.1002/adfm.201100218 · 11.81 Impact Factor
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    ABSTRACT: Rapamycin is a macrocyclic polyketide with immunosuppressive, antifungal, and anticancer activity produced by Streptomyces hygroscopicus ATCC 29253. Rapamycin production by a mutant strain (UV2-2) induced by ultraviolet mutagenesis was improved by approximately 3.2-fold (23.6 mg/l) compared to that of the wild-type strain. The comparative analyses of gene expression and intracellular acyl-CoA pools between wild-type and the UV2-2 strains revealed that the increased production of rapamycin in UV2-2 was due to the prolonged expression of rapamycin biosynthetic genes, but a depletion of intracellular methylmalonyl-CoA limited the rapamycin biosynthesis of the UV2-2 strain. Therefore, three different metabolic pathways involved in the biosynthesis of methylmalonyl-CoA were evaluated to identify the effective precursor supply pathway that can support the high production of rapamycin: propionyl-CoA carboxylase (PCC), methylmalonyl-CoA mutase, and methylmalonyl-CoA ligase. Among them, only the PCC pathway along with supplementation of propionate was found to be effective for an increase in intracellular pool of methylmalonyl-CoA and rapamycin titers in UV2-2 strain (42.8 mg/l), indicating that the PCC pathway is a major methylmalonyl-CoA supply pathway in the rapamycin producer. These results demonstrated that the combined approach involving traditional mutagenesis and metabolic engineering could be successfully applied to the diagnosis of yield-limiting factors and the enhanced production of industrially and clinically important polyketide compounds.
    Applied Microbiology and Biotechnology 06/2011; 91(5):1389-97. DOI:10.1007/s00253-011-3348-6 · 3.34 Impact Factor
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    ABSTRACT: Streptomyces venezuelae YJ028, bearing a deletion of the entire biosynthetic gene cluster encoding the pikromycin polyketide synthases and desosamine biosynthetic enzymes, was used as a bioconversion system for combinatorial biosynthesis of glycosylated derivatives of tylosin. Two engineered deoxysugar biosynthetic pathways for the biosynthesis of TDP-3-O-demethyl-D-chalcose or TDP-Lrhamnose in conjunction with the glycosyltransferaseauxiliary protein pair DesVII/DesVIII were expressed in a S. venezuelae YJ028 mutant strain. Supplementation of each mutant strain capable of producing TDP-3-O-demethyl- D-chalcose or TDP-L-rhamnose with tylosin aglycone tylactone resulted in the production of the 3-O-demethyl- D-chalcose, D-quinovose, or L-rhamnose-glycosylated tylactone.
    Journal of Microbiology and Biotechnology 06/2011; 21(6):613-6. DOI:10.4014/jmb.1103.03032 · 1.53 Impact Factor

Publication Stats

281 Citations
109.57 Total Impact Points


  • 2007-2015
    • Ewha Womans University
      • • Department of Chemistry Nano Science
      • • Center for Cell Signaling and Drug Discovery Research
      Sŏul, Seoul, South Korea
  • 2014
    • Korea University
      Sŏul, Seoul, South Korea
  • 2006-2014
    • Seoul National University
      • • Department of Forest Sciences
      • • School of Chemical and Biological Engineering
      Sŏul, Seoul, South Korea
  • 2013
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      • Targeted Medicine Research Center
      Anzan, Gyeonggi-do, South Korea
  • 2012
    • Kangwon National University
      • Department of Biological Environment
      Shunsen, Gangwon-do, South Korea