Hyungdon Yun

Konkuk University, Sŏul, Seoul, South Korea

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Publications (53)169.43 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In general, conventional enzyme engineering utilizes 20 canonical amino acids to alter and improve the functional properties of proteins such as stability, and activity. In this study, we utilized the noncanonical amino acid incorporation technique to enhance the functional properties of ω-transaminase (ω-TA). Herein, we enhanced the stability of ω-TA by residue-specific incorporation of (4R)-fluoroproline [(4R)-FP] and successfully immobilized onto chitosan or polystyrene (PS) beads with site-specifically incorporated L-3,4-dihydroxyphenylalanine (DOPA) moiety. The immobilization of ω-TAdopa and ω-TAdp[(4R)-FP] onto PS beads showed excellent reusability for 10 cycles in the kinetic resolution of chiral amines. Compared to the ω-TAdopa, the ω-TAdp[(4R)-FP] immobilized onto PS beads exerted more stability that can serve as suitable biocatalyst for the asymmetric synthesis of chiral amines.
    ChemCatChem 12/2014; · 5.18 Impact Factor
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    ABSTRACT: Lead is one of the most hazardous metals ubiquitous in the environment, causing serious health hazards to organisms. Recently, fluorescent proteins such as GFP and Dsred were utilized for the development of reagent-less rapid metal sensors. Here, we demonstrate the development of a lead-sensing GFP that is highly sensitive to lead in micro molar concentrations
    Chemical Communications 11/2014; · 6.38 Impact Factor
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    ABSTRACT: The iLOV protein belongs to a family of blue-light photoreceptor proteins containing a light-oxygen-voltage sensing domain with a non-covalently bound flavin mononucleotide (FMN) as its chromophore. Due to advantages such as small size, oxygen-independent nature, and pH stability, iLOV is an ideal candidate over other reporter fluorescent proteins such as GFP and DsRed. Here, for the first time, we describe the feasibility of applying LOV domain-based fluorescent iLOV as a metal sensor by measuring the fluorescence quenching of a protein with respect to the concentration of metal ions. In the present study, we demonstrate the inherent copper sensing property of the iLOV protein and identify the possible amino acids responsible for metal binding. The fluorescence quenching upon exposure to Cu(2+) was highly sensitive and exhibited reversibility upon the addition of the metal chelator EDTA. The copper binding constant was found to be 4.72 ± 0.84 µM. In addition, Cu(2+)-bound iLOV showed high fluorescence quenching at near physiological pH. Further computational analysis yielded a better insight into understanding the possible amino acids responsible for Cu(2+) binding with the iLOV protein.
    Journal of microbiology and biotechnology. 10/2014;
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    ABSTRACT: Misaminoacylation of 3,4-dihydroxyphenylalanine (Dopa) molecules to tRNATyr by endogenous tyrosyl-tRNA synthetase allowed the quantitative replacement of tyrosine residues with a yield of over 90 % by an in vivo residue-specific incorporation strategy, to create, for the first time, engineered mussel adhesive proteins (MAPs) in Escherichia coli with a very high Dopa content, close to that of natural MAPs. The Dopa-incorporated MAPs exhibited a superior surface adhesion and water resistance ability by assistance of Dopa-mediated interactions including the oxidative Dopa cross-linking, and furthermore, showed underwater adhesive properties comparable to those of natural MAPs. These results propose promising use of Dopa-incorporated engineered MAPs as bioglues or adhesive hydrogels for practical underwater applications.
    Angewandte Chemie 09/2014;
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    ABSTRACT: In this study, we successfully synthesized enantiomerically pure (R)- and (S)-γ-amino acids (>99% ee) using ω- transaminase (ω-TA) through kinetic resolution and asymmetric synthesis respectively. The present study demonstrates the high potentiality of ω-TA reaction for the production of chiral γ-amino acids.
    Chemical Communications 08/2014; · 6.38 Impact Factor
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    ABSTRACT: Daidzein C6 hydroxylase (6-DH, nfa12130), which is a class I type of cytochrome P450 enzyme, catalyzes a hydroxylation reaction at the C6-position of the daidzein A-ring and requires auxiliary electron transfer proteins. Current utilization of cytochrome P450 (CYP) enzymes is limited by low coupling efficiency, which necessitates extramolecular electron transfers, and low driving forces, which derive electron flows from tightly regulated NADPH redox balances into the heterogeneous CYP catalytic cycle. To overcome such limitations, the heme domain of the 6-DH enzyme was genetically fused with the NADPH-reductase domain of self-sufficient CYP102D1 to enhance electron transfer efficiencies through intramolecular electron transfer and switching cofactor preference from NADH into NADPH. 6-DH-reductase fusion enzyme displayed distinct spectral properties of both flavoprotein and heme proteins and catalyzed daidzein hydroxylation more efficiently with a k cat/K m value of 120.3 ± 11.5 [10(3) M(-1) s(-1)], which was about three times higher than that of the 6-DH-FdxC-FdrA reconstituted system. Moreover, to obtain a higher redox driving force, a Streptomyces avermitilis host system was developed for heterologous expression of fusion 6-DH enzyme and whole cell biotransformation of daidzein. The whole cell reaction using the final recombinant strain, S. avermitilisΔcyp105D7::fusion 6-DH (nfa12130), resulted in 8.3 ± 1.4 % of 6-OHD yield from 25.4 mg/L of daidzein.
    Applied Microbiology and Biotechnology 04/2014; · 3.81 Impact Factor
  • Advanced Synthesis & Catalysis 03/2014; · 5.54 Impact Factor
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    ABSTRACT: Here we enhanced the stability and biophysical properties of mRFP1 through a combination of canonical and non-canonical amino acid mutagenesis. The global replacement of proline residue with (2S, 4R)-4-fluoroproline [(4R)-FP] into mRFP1 led to soluble protein but lost its fluorescence, whereas (2S, 4S)-4-fluoroproline [(4S)-FP] incorporation resulted in insoluble protein. The bioinformatics analysis revealed that (4R)-FP incorporation at Pro63 caused fluorescence loss due to the steric hindrance of fluorine atom of (4R)-FP with the chromophore. Therefore, Pro63 residue was mutated with the smallest amino acid Ala to maintain non coplanar conformation of the chromophore and helps to retain its fluorescence with (4R)-FP incorporation. The incorporation of (4R)-FP into mRFP1-P63A showed about 2∼3 fold enhancement in thermal and chemical stability. The rate of maturation is also greatly accelerated over the presence of (4R)-FP into mRFP1-P63A. Our study showed that a successful enhancement in the biophysical property of mRFP1-P63A[(4R)-FP] using non-canonical amino acid mutagenesis after mutating non-permissive site Pro63 into Ala.
    Biochemical and Biophysical Research Communications 09/2013; · 2.28 Impact Factor
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    ABSTRACT: In this study, we developed a one-pot one-step deracemization method for the production of various enantiomerically pure amines using two opposite enantioselective ω-TAs. Using this method, various aromatic amines were successfully converted to their (R)-forms (>99%) with good conversion.
    Chemical Communications 06/2013; · 6.38 Impact Factor
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    ABSTRACT: A current challenge in high-throughput screening (HTS) of hydroxylation reactions by P450 is a fast and sensitive assay for regioselective hydroxylation against millions of mutants. We have developed a solid-agar plate-based HTS assay for screening ortho-specific hydroxylation of daidzein by sensing formaldehyde generated from the O-dealkylation reaction. This method adopts a colorimetric dye, pararosaniline, which has previously been used as an aldehyde-specific probe within cells. The rationale for this method lies in the fact that the hydroxylation activity at ortho-carbon position to COH correlates with a linear relationship to O-dealkylation activity on chemically introduced methoxy group at the corresponding COH. As a model system, a 4',7-dihydroxyisoflavone (daidzein) hydroxylase (CYP102D1 F96V/M246I), which catalyzes hydroxylation at ortho positions of the daidzein A/B-ring, was examined for O-dealklyation activity, by using permethylated daidzein as a surrogate substrate. By using the developed indirect bishydroxylation screening assay, the correlation coefficient between O-dealkylation and bishydroxylation activity for the template enzyme was 0.72. For further application of this assay, saturation mutants at A273/G274/T277 were examined by mutant screening with a permethylated daidzein analogue substrate (A-ring inactivated in order to find enhanced 3'-regioselectiviy). The whole-cell biotransformation of daidzein by final screened mutant G1 (A273H/G274E/T277G) showed fourfold increased conversion yield, with 14.3 mg L(-1) production titer and greatly increased 3'-regioselectiviy (3'/6=11.8). These results show that there is a remarkably high correlation (both in vitro and in vivo), thus suggesting that this assay would be ideal for a primary HTS assay for P450 reactions.
    ChemBioChem 06/2013; · 3.74 Impact Factor
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    ABSTRACT: Recently, ω-transaminases have been increasingly used to synthesize amine compounds by reductive amination of prochiral ketones which are of high pharmacological significance. However, the conventional methods for evaluating these enzymes are time consuming and have often been regarded as a bottle neck in developing these enzymes as industrial biocatalysts. In the past few years, several high throughput screening methods have been developed for fast evaluation and identification of ω-transaminase. This review summarizes the various methodologies developed for rapidly screening ω-transaminases.
    Biotechnology and Bioprocess Engineering 02/2013; 18:1-7. · 1.28 Impact Factor
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    ABSTRACT: Residue-specific incorporation is a technique used to replace natural amino acids with their close structural analogs, unnatural amino acids (UAAs), during protein synthesis. This is achieved by exploiting the substrate promiscuity of the wild type amino acyl tRNA synthetase (AARS) towards the close structural analogs of their cognate amino acids. In the past few decades, seleno-methionine was incorporated into proteins, using the substrate promiscuity of wild type AARSs, to resolve their crystal structures. Later, the incorporation of many UAAs showed that the AARSs are polyspecific to the close structural analogs of their cognate amino acids and that they maintain fidelity for the 19 natural amino acids. This polyspecificity helps to expand the use of this powerful tool to incorporate various UAA residues specifically through in vivo and in vitro approaches. Incorporation of UAAs is expensive, tedious and time-consuming. For the efficient incorporation of UAAs, it is important to screen substrate selectivity prior to their incorporation. As an initial study, using a docking tool, we analyzed the polyspecificity of the methionyl-tRNA synthetases (MetRSs) towards multiple reported and virtually generated methionine analogs. Based on the interaction result of these docking simulations, we predicted the substrate selectivity of the MetRS and the key residues responsible for the recognition of methionine analogs. Similarly, we compared the active site residues of the MetRSs of different species and identified the conserved amino acids in their active sites. Given the close similarity in the active site residues of these systems, we evaluated the polyspecificity of MetRSs.
    Journal of molecular graphics & modelling 11/2012; 39C:79-86. · 2.17 Impact Factor
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    ABSTRACT: Phenolic acid decarboxylase (PAD) catalyzes the non-oxidative decarboxylation of p-coumaric acid (pCA) to p-hydroxystyrene (pHS). PAD from Bacillus amyloliquefaciens (BAPAD), which showed k (cat)/K (m) value for pCA (9.3 × 10(3) mM(-1) s(-1)), was found as the most active one using the "Subgrouping Automata" program and by comparing enzyme activity. However, the production of pHS of recombinant Escherichia coli harboring BAPAD showed only a 22.7 % conversion yield due to product inhibition. Based on the partition coefficient of pHS and biocompatibility of the cell, 1-octanol was selected for the biphasic reaction. The conversion yield increased up to 98.0 % and 0.83 g/h/g DCW productivity was achieved at 100 mM pCA using equal volume of 1-octanol as an organic solvent. In the optimized biphasic reactor, using a three volume ratio of 1-octanol to phosphate buffer phase (50 mM, pH 7.0), the recombinant E. coli produced pHS with a 88.7 % conversion yield and 1.34 g/h/g DCW productivity at 300 mM pCA.
    Applied Microbiology and Biotechnology 10/2012; · 3.81 Impact Factor
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    ABSTRACT: A cytochrome P450 (CYP) enzyme, 3'-daidzein hydroxylase, CYP105D7 (3'-DH), responsible for daidzein hydroxylation at the 3'-position, was recently reported. CYP105D7 (3'-DH) is a class I type of CYP that requires electrons provided through electron transfer proteins such as ferredoxin and ferredoxin reductase. Presently, we constructed an artificial CYP in order to develop a reaction host for the production of a hydroxylated product. Fusion-mediated construction with the reductase domain from self-sufficient CYP102D1 was done to increase electron transfer efficiency and coupling with the oxidative process. An artificial self-sufficient daidzein hydroxylase (3'-ASDH) displayed distinct spectral properties of both flavoprotein and CYP. The fusion enzyme catalyzed hydroxylation of daidzein more efficiently, with a kcat/Km value of 16.8 μM-1 min-1, which was about 24-fold higher than that of the 3'-DH-camA/B reconstituted enzyme. Finally, a recombinant Streptomyces avermitilis host for the expression of 3'-ASDH and production of the hydroxylated product was developed. The conversion that was attained (34.6%) was 5.2-fold higher than that of the wild-type.
    Microbial Cell Factories 06/2012; 11:81. · 3.31 Impact Factor
  • Journal of Molecular Catalysis B Enzymatic 06/2012; 78:57-64. · 2.82 Impact Factor
  • Sam Mathew, Hyungdon Yun
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    ABSTRACT: Transaminases have been increasingly used as efficient biocatalysts due to their ability to produce a wide range of optically pure amine compounds. Several approaches have been adopted, including screening, engineering, and develop-ment of new techniques in reaction systems for different aspects of the enzymes. This review summarizes the various methodologies and approaches adopted to produce enantio-merically pure amines and unnatural amino acids using ω-transaminases.
    ACS Catalysis 04/2012; 2(6):993-1001. · 5.27 Impact Factor
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    ABSTRACT: A deracemization method was developed to generate optically pure L-homoalanine from racemic homoalanine using D-amino acid oxidase and ω-transaminase. A whole cell reaction using a biphasic system converted 500 mM racemic homoalanine to 485 mM L-homoalanine (>99% ee).
    Organic & Biomolecular Chemistry 03/2012; 10(12):2482-5. · 3.57 Impact Factor
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    ABSTRACT: l-6-Hydroxynorleucine was synthesized from 2-keto-6-hydroxyhexanoic acid using branched-chain aminotransferase from Escherichia coli with l-glutamate as an amino donor. Since the branched-chain aminotransferase was severely inhibited by 2-ketoglutarate, the branched-chain aminotransferase reaction was coupled with aspartate aminotransferase and pyruvate decarboxylase. Aspartate aminotransferase converted the inhibitory 2-ketoglutarate back to l-glutamate by using l-aspartate as an amino donor. On the other hand, pyruvate decarboxylase further shifted the reaction equilibrium towards l-6-hydroxynorleucine through decarboxylation of pyruvate to acetaldehyde. The concerted action of the three enzymes significantly enhanced the yield compared to that of branched-chain aminotransferase alone. In the coupled reaction, 90.2 mM l-6-hydroxynorleucine (> 99% ee) was produced from 100 mM 2-keto-6-hydroxyhexanoic acid, whereas in a single branched-chain aminotransferase reaction only 22.5 mM l-6-hydroxynorleucine (> 99% ee) was produced.
    Biocatalysis and Biotransformation 03/2012; 30(2). · 0.90 Impact Factor
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    ABSTRACT: Recently, non-canonical amino acids (NCAA) incorporation was developed to enhance the functional properties of proteins. Incorporation of NCAA containing chlorine atom is conceptually an attractive approach to prepare pharmacologically active substances, which is a difficult task since chlorine is bulky atom. In this study, we evaluated the efficiency and extent of in vivo incorporation of tyrosine analogue 3-chlorotyrosine [(3-Cl)Tyr] into the recombinant proteins GFP and GFPHS (highly stable GFP). The incorporation of (3-Cl)Tyr into GFP leads to dramatic reduction in the expression level of protein. On the other hand, the incorporation of (3-Cl)Tyr into GFPHS was expressed well as a soluble form. In addition we used bioinformatics tools for the analysis to explore the possible constraints in micro-environment of each natural amino acid residue to be replaced with chlorine atom accommodation into GFPHS. In conclusion, our approaches are reliable and straightforward way to enhance the translation of chlorinated amino acids into proteins.
    Biotechnology and Bioprocess Engineering 03/2012; 17(6):679-. · 1.28 Impact Factor
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    ABSTRACT: CYP51, a sterol 14α-demethylase, is one of the key enzymes involved in sterol biosynthesis and requires electrons transferred from its redox partners. A unique CYP51 from Nocardia farcinica IFM10152 forms a distinct cluster with iron-sulfur containing NADPH-P450 reductase (FprD) downstream of CYP51. Previously, sequence alignment of nine reductases from N. farcinica revealed that FprC, FprD, and FprH have an additional sequence at their N-termini that has very high identity with iron-sulfur clustered ferredoxin G (FdxG). To construct an artificial self-sufficient cytochrome P450 monooxygenase (CYP) with only FprD, CYP51, and iron-sulfur containing FprD were fused together with designed linker sequences. CYP51-FprD fusion enzymes showed distinct spectral properties of both flavoprotein and CYP. CYP51-FprD F1 and F2 in recombinant Escherichia coli BL21(DE3) catalyzed demethylation of lanosterol more efficiently, with k(cat) /K(m) values of 96.91 and 105.79 nmol/min/nmol, respectively, which are about 35-fold higher compared to those of CYP51 and FprD alone.
    Biotechnology and Bioengineering 03/2012; 109(3):630-6. · 4.16 Impact Factor

Publication Stats

357 Citations
169.43 Total Impact Points


  • 2014
    • Konkuk University
      • Department of Bioscience and Technology
      Sŏul, Seoul, South Korea
  • 2008–2013
    • Yeungnam University
      • School of Biotechnology
      Asan, South Chungcheong, South Korea
  • 2003–2013
    • Seoul National University
      • • Department of Chemical and Biological Engineering
      • • School of Chemical and Biological Engineering
      Seoul, Seoul, South Korea