• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.15-15
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• 2002

• Korean Journal of Pharmacognosy
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• v.52 no.4
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• pp.208-211
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• 2021

Four compounds were isolated from 90% ethanol extract of the stem of Clematis heracleifolia. On the basis of spectral data, the structure of isolated compounds were identified as sitosterone (1), β-sitosterol (2), scoparone (3) and octadecanoyl caffeate (4), respectively. Sitosterone (1) and octadecanoyl caffeate (4) are isolated from this plant for the first time.

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.2
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• pp.77-85
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• 2004

$^1$H-detected $^{15}$N NMR was employed to investigated the effect of mutation (Y14F) on the dynamic properties of catalytic residues in ${\Delta}^5$-3- ketosteroid isomerase (KSI) from Conamonas testosteroni. In particular, the backbone dynamics of the catalytic residues have been studied in free enzyme and its complex with a steroid ligand, 19-nortestosterone hemisuccinate, by $^{15}$N relaxation measurements. The relaxation data were analyzed using the model-free formalism to extract the model-free parameters (S$^2$, ${\tau}_e$, and R$_{ex}$). The results show that the mutation causes a significant decrease in the order parameter (S$^2$) for the catalytic residues of free Y14F KSI, presumably due to breakdown of the hydrogen bond network by mutation. In addition, the order parameters of Phe-14 and Asp-99 increased slightly upon ligand binding, indicating a slight restriction of the high-frequency (pico- to nanosecond) internal motions of the residues in the complexed Y14F KSI, while the order parameter of Tyr-55 decreased significantly upon ligand binding.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.33-33
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• 2001

Bacterial Δ$\^$5/-3-ketosteroid isomerase (KSI) is one of the most proficient enzymes catalyzing the isomerization of a variety of Δ$\^$5/-ketosteroids to Δ$^4$-ketosteroids at a diffusion-controlled rate. Because of the simplicity of the reaction, the enzyme mechanism has been intensively studied as a prototype to understand enzyme-catalyzed C-H bond cleavage.(omitted)

• Journal of Sericultural and Entomological Science
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• v.52 no.1
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• pp.45-51
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• 2014

A cecropin-A gene was isolated from the immunized larvae of the Japanese oak silkworm, Antheraea yamamai and designed Ay-CecA. The complete Ay-CecA cDNA consists of 419 nucleotides with 195 bp open reading frame encoding a 64 amino acid precursor that contains a putative 22-residue signal peptide, a 4-residue propetide and a 37-residue mature peptide with a theoretical mass of 4046.81. The deduced amino acid sequence of the peptide evidenced a significant degree of identity (62 ~ 78% identity) with other lepidopteran cecropins. Like many insect cecropin, Ay-CecA also harbored a glycine residue for C-terminal amidation at the C-end, which suggests potential amidation. To understand this peptide better, we successfully expressed bioactive recombinant Ay-CecA in Escherichia coli that are highly sensitive to the mature peptide. For this, we fused mature Ay-CecA gene with insoluble protein ketosteroid isomerase (KSI) gene to avoid the cell death during induction. The fusion KSI-CecA protein was expressed as inclusion body. The expressed fusion protein was purified by Ni-NTA immobilized metal affinity chromatography (IMAC), and cleaved by cyanogen bromide (CNBr) to release recombinant Ay-CecA. The purified recombinant Ay-CecA showed considerably antibacterial activity against Gram-negative bacteria, E. cori ML 35, Klebsiella pneumonia and Pseudomonas aeruginosa. Our results proved that this peptide with a potent antibacterial activity may play a role in the immune response of Japanese oak silkworm.

• Archives of Pharmacal Research
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• v.3 no.1
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• pp.1-6
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• 1980

As part of our endeavor to increase the productivity of steroid by enzymatic transformation of corticosteroids, attempts have been made to increase the solubility of steroids by using some organic solvents. When the solubility of steroids is the rate limiting factor in the steroid transformation, it was found that the use of solvents significantly improved the yield. Hydrocorisone as a substrate and 3-ketosteroid .DELTA.$^{1}$ dehydrogense as an immobilized whole cell enzyme were employed as the model system for this study. It was found that the yield of product, prodnisolone, goes through a maximum with an increase in the solvent concentration. At a high solvent concentration, the solvent showed a toxic effect and it causes a decrease in the product yield by the second order inhibition mechanism. Among the solvents evaluated, methanol and ethanol were found to be the best. These alcohols are not only good solvents but also showed minimal toxic effect. Based on the experimental results, it was concluded that the productivity of steroid can be increased by usign well selcted solvents systems for the enzymatic transformation of steroids.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.411-416
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• 1990

Microbiological conversion of sterols to 17-ketosteroids has been recongnized as a source for commerical preparation of steroidal drugs. For the purpose of strain development, we isolated microorganisms through enrichment culture method and identified an isolate strain. The strain was closely related to Brevibacterium ergthrogenes. The optimal conditions for 1, 4-androstadiene-3, 17-dione (ADD) formation were as follows; pH 7.4, lactose 0.2%, beef extract 0.2%, bentonite 0.5% in the chlolesterol fermentation medium. Maximum production was obtained with the addition of $\alpha$, $\alpha$'-dipyridyl (1 mM, final conc.) at 17-20 hours after incubation.