• BMB Reports
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• v.28 no.4
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• pp.363-367
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• 1995

E. coli methionyl-tRNA synthetase is one of the class I tRNA synthetases. The Tryptophane residue at the position 461 located in the C-terminal domain of the enzyme is a key amino acid for the interaction with the anticodon of $tRNA^{Met}$. W461 was replaced with other amino acids to determine the chemical requirement for the interaction with the anticodon of $tRNA^{Met}$. Saturation mutagenesis at the position 461 generated a total of 12 substitution mutants of methionyl-tRNA synthetase. All the mutants showed the same in vivo stability as the wild-type enzyme, suggesting that the amino acid substitutions did not cause severe conformational change of the protein The mutants containing tyrosine, phenylalanine, histidine and cysteine substitutions showed in vivo activity while all the other mutants did not. The comparison of the in vitro aminoacylation activities of these mutants showed that aromatic ring structure, Van der Waals volume and hydrogen bond potential of the amino acid residue at the position 461 are the major determinants for the interaction with the anticodon of $tRNA^{Met}$.

• Journal of Microbiology and Biotechnology
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• v.28 no.10
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• pp.1581-1588
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• 2018

The growth of lactic acid bacteria (LAB) generates a high number of metabolites related to aromas and flavors in fermented dairy foods. These microbial proteases are involved in protein hydrolysis that produces necessary peptides for their growth and releases different molecules of interest, like bioactive peptides, during their activity. Each genus in particular has its own proteolytic system to hydrolyze the necessary proteins to meet its requirements. This review aims to highlight the differences between the proteolytic systems of Streptococcus thermophilus and other lactic acid bacteria (Lactococcus and Lactobacillus) since they are microorganisms that are frequently used in combination with other LAB in the elaboration of fermented dairy products. Based on genetic studies and in vitro and in vivo tests, the proteolytic system of Streptococcus thermophilus has been divided into three parts: 1) a serine proteinase linked to the cellular wall that is activated in the absence of glutamine and methionine; 2) the transport of peptides and oligopeptides, which are integrated in both the Dpp system and the Ami system, respectively; according to this, it is worth mentioning that the Ami system is able to transport peptides with up to 23 amino acids while the Opp system of Lactococcus or Lactobacillus transports chains with less than 13 amino acids; and finally, 3) peptide hydrolysis by intracellular peptidases, including a group of three exclusive of S. thermophilus capable of releasing either aromatic amino acids or peptides with aromatic amino acids.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.280.2-280
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• 1997

No Abstract, See Full Text

• Natural Product Sciences
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• v.4 no.3
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• pp.115-129
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• 1998

The chemical constituents and their biological activities of the sponge genus Dysidea has been reviewed.

• Proceedings of the PSK Conference
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• 2000.10a
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• pp.248.2-248.2
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• 2000

• Korean Journal of Pharmacognosy
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• v.32 no.1 s.124
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• pp.49-54
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• 2001

The effects of protoberberine compounds on serotonin biosynthesis in P815 cells were investigated. Protoberberine compounds such as berberine, palmatine and coralyne decreased serotonin content dose-dependently, but coptisine did not. The $IC_{50}$ values of berberine, palmatine and coralyne were $3.0\;{\mu}M,\;16.5\;{\mu}M\;and\;14.5\;{\mu}M$, respectively. Protoberberine compounds at concentrations up to $20\;{\mu}M$ were not cytotoxic towards P815 cells. The activity of tryptophan hydroxylase, a ratelimiting enzyme in serotonin biosynthesis, was inhibited by the exposure of berberine, palmatine and coralyne in P815 cells (14.9-19.3% inhibition at $2-15\;{\mu}M$), but that of aromatic L-amino acid decarboxylase was not. These results suggest that the inhibition of tryptophan hydroxylase activity by berberine, palmatine and coralyne might partially contribute to the decrease in serotonin content in P815 cells.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.2
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• pp.333-339
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• 2008

Korean ginseng (Panax ginseng C. A. Meyer) has been used as an important medicinal plant in the Orient for a long time. It has been claimed that ginseng has many beneficial bioactive effects on human health, such as antitumor, antistress, antiaging and enhancing immune functions. Red ginseng possibly have new ingredients converted during steaming and dry process from fresh ginseng. Kujeungkupo method which means 9 repetitive steaming and drying process was used for the processes of green tea, Polygonatum odoratum, and Rehmanniae radix preparata. In this study, ingredient conversion of ginseng by 9 repetitive steaming and drying process were investigated measuring conversion efficiency of brown materials, crude lipids, crude proteins and aromatic compounds. Brown materials, as an antioxidant, in red ginseng were produced through non-enzymatic reaction by heat. Repetitive steaming and drying treatments on ginseng root contiunously increased the content of brown materials and the chromaticity. Crude lipids were degraded by heat and converted into volatile aromatic ingredients. Crude lipids were degraded and decreased by 0.52% after the 5th and 7th. Crude proteins were also decomposed and converted to amino acid. Crude proteins after the 9th treatment were decreased by more than 85% as increased times of treatments. A bicyclogermacrene as aromatic material was decreased as increased treatment times, while but a aromatic caramel was increased.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.217-222
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• 2006

Polyimides have been investigated extensively and used widely over the past three decades because of their high performance properties such as excellent thermal, mechanical, and electrical properties. Polyimides are difficult to be processed because of the aromatic moieties, imide group, and insoluble nature in most organic solvents. The soluble polyimides were synthesized from 2,2,-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (BAPAF) and 3,3,-diamino-4,4-dihydroxybyphenyl (HAB) as aromatic diamines and 4,4-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), pyromellitic dianhydride (PMDA), 4,4-oxydiphthalic dianhydride (OPDA), 3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA) and 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride (DSDA) as aromatic dianhydrides. The polyimides were characterized by NMR, FR-IR, TGA and the dielectric constant of the obtained polyimides was calculated from storage of electro-capacity. A novel photosensitive polyimide was synthesized by the reaction of polyimide, containing hydroxyl group and methacryloyl chloride using triethylamine. The good micro-pattern was obtained with photosensitive polyimide from the photolithographic technique.

• Journal of Radiation Industry
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• v.10 no.4
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• pp.181-187
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• 2016

Selective ${\beta}_1$-agonist and antagonists are used for the treatment of cardiac diseases including congestive heart failure, angina pectoris and arrhythmia. Selective ${\beta}_1$-antagonists including nebivolol have high binding affinity on ${\beta}_1$-adrenergic receptor, not ${\beta}_2$-receptor mainly expressed in smooth muscle. Nebivolol is one of most selective ${\beta}_1$-blockers in clinically used ${\beta}_1$-blockers including atenolol and bisoprolol. We tried to develop clinically useful cardiac PET tracers using a selective ${\beta}_1$-blocker. Nebivolol is $C_2$-symmetric and has two chromane moiety with a secondary amino alcohol and aromatic fluorine. We adopted the general synthetic strategy using epoxide ring opening reaction. Unlike formal synthesis of nebivolol, we prepared two chromane building blocks with fluorine and iodine which was transformed to diaryliodonium salt for labelling of $^{18}F$. Two epoxide building blocks were readily prepared from commercially available chromene carboxylic acids (1, 8). Then, the amino alcohol building block (15) was prepared by ammonolysis of epoxide (14) followed by coupling reaction with the other building block, epoxide (7). Diaryliodonium salt, a precursor for $^{18}F$-aromatic substitution, was synthesized in moderate yield which was readily subjected to $^{18}F$-aromatic substitution to give $^{18}F$-labelled nebivolol.

• Journal of Microbiology
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• v.44 no.1
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• pp.50-53
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• 2006

Cys-29 and Cys-251 of Streptomyces albus valine dehydrogenase(ValDH) were highly conserved in the corresponding region of $NAD(P)^+$-dependent amino acid dehydroganase sequences. To ascertain the functional role of these cysteine residues in S. albus ValDH, site-directed mutagenesis was performed to change each of the two residues to serine. Kinetic analyses of the enzymes mutated at Cys-29 and Cys-251 revealed that these residues are involved in catalysis. We also constructed mutant ValDH by substituting valine for leucine at 305 by site-directed mutagenesis. This residue was chosen, because it has been proposed to be important for substrate discrimination by phenylalanine dehydrogenase (PheDH) and leucine dehydrogenase (LeuDH). Kinetic analysis of the V305L mutant enzyme revealed that it is involved in the substrate binding site. However it displayed less activity than the wild type enzyme toward all aliphatic and aromatic amino acids tested.