• Archives of Pharmacal Research
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• v.24 no.4
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• pp.292-296
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• 2001

Three prolyl endopeptidase (PEP) inhibitors were isolated from the methanolic extract of green tea leaves. They were identified as (-)-epigallocatechin gallate, (-)-epicatechin gallate, and (+)-gallucatechin gallate with the $IC_{50}$ values of 1.42${\times}$$10^{-4}$mM, $1.02{\times}10^{-2}$mM, and $1.09{\times}10^{-4}$mM, respectively. They were non-competitive with a substrate in Dixon plots and did not show any significant effects against other serine proteases such as elastase, trypsin, and chymotrypsin, suggesting that they were relatively specific inhibitors against PER The isolated compounds are expected to be useful for preventing and curing of Alzheimer's disease.

• Toxicological Research
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• v.14 no.4
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• pp.557-562
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• 1998

Allyl alcohol is metabolized in the liver through two steps, first to reactive acrolein by alcohol dehydrogenase (ADH), subsequently to acrylic acid by aldehyde dehydrogenase (ALDH). Since ethanol could compete the same enzymes to be metabolized in the liver, we have determined the plasma concentrations of allyl alcohol and ethanol followed by combined treatment. Pretreatment of rats with 2g/kg ethanol followed by ip administration of 40mg/kg allyl alcohol increased the lethality significantly. Determination of in vivo blood concentrations revealed that ethanol pretreatment caused the apparent decrease in allyl alcohol clearance, whereas acetaldehyde level in blood increased significantly by allyl alcohol treatment, as determined by head space GC analysis. Treatment of 4-methylpyrazole, an inhibitor of ADH, delayed allyl alcohol elimination significantly and reduced its lethality. Collectively, these findings suggested that reduction of allyl alcohol clearance in the presence oj ethanol was mediated through ADH competitive inhibition.

• Bulletin of the Korean Chemical Society
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• v.3 no.3
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• pp.122-129
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• 1982

In order to extend our understanding on the multiple inhibition enzyme kinetics, a general equation of an enzyme reaction in the presence of two different reversible inhibitors was derived by what we call "match-box mechanism" under the combined assumption of steady-state and quasi-equilibrium for inhibitor binding. Graphical methods were proposed to analyze the multiple inhibition of an enzyme by any given sets of different inhibitors, i.e., competitive, noncompetitive, and uncompetitive inhibitors. This method not only gives an interaction factor $({\alpha})$ between two inhibitors, but also discerns ${\alpha}_1$ and ${\alpha}_2$ with and without substrate binding, respectively. The factors involved in the dissociation constants of inhibitors can also be evaluated by the present plot. It is also shown that the present kinetic approach can be extended to other forms of activators or hydrogen ions with some modification.

• Journal of Food Hygiene and Safety
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• v.2 no.4
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• pp.181-189
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• 1987

To find esterase inhibitors and in the metabolites of Streptomyces strain DMC-498, two active compounds were isolated from the methanol extract of the mycelia of the strain by Silica gel column chromatography and preparatory argentation TLC. These compounds were proved to show competitive inhibition. Compound B was found to consist of linoleic and oleic acids. Fifty percent inhibition concentration ($lC_{50}$) of linoleic acid was $0.045\mu\textrm{g}/ml$, whereas oleic acid exhibited no inhibitory activity. Associated lipids: isostearic acid, isostearic acid methyl ester, oleic acid methyl ester and linoleic acid methyl ester, were isolated from the same extract, showing no inhibition of the esterase. Compound A was found to be a liquid inhibitor with an alicyclic ring and two or more oxygens, its molecular weight being more than 500.

• Korean Journal of Food Science and Technology
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• v.20 no.1
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• pp.79-84
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• 1988

${\alpha}$-Galactosidase from Aspergillus niger as a possible enzyme for removal of flatulence factors in soybean foods was produced the highest in 120 hours in either Czapeck-Dox liquid medium or wheat bran solid medium. The most efficient carbon and nitrogen sources in Czapeck-Dox medium were raffinose and sodium nitrate, respectively, whereas the addition of the sources showed negative effects in wheat bran. pH optima for enzyme activity and stability were 4.0-5.0 and 3.5-6.5, respectively, and optimum temperature for stability was $40-50^{\circ}C$. Upon reaction on p-nitrophenyl-${\alpha}$-D-galactoside, Michaelis constant was 0.42 mM and maximum velocity was 152 ${\mu}moles$ substrate/minute/kg solid medium. Mercuric chloride acted as a strong noncompetitive inhibitor and p-chloromercuribenzoate, even in low concentration, acted as a competitive inhibitor. Crude ${\alpha}$-galactosidase hydrolyzed raffinose and stachyose completely, giving spots of monosaccharides only on thin-layer chromatogram.

• Proceedings of the Microbiological Society of Korea Conference
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• 2004.05a
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• pp.65-67
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• 2004

O-GlcNAcylation of p53 has been already identified and reported, but the function of O-GlcNAc on p53 has not been studied well. In this report, the general function of O-GlcNAc modification on p53 has been investigated using mouse fibroblast cell, L929. When streptozotocin (STZ), a non-competitive O-GlcNAcase inhibitor was treated to L929, O-GlcNAc modification level was dramatically increased on nucleocytoplasmic proteins, including p53. Because it has been already reported that $TNF\alpha$ induced the production of p53 in L929, $TNF\alpha$ was treated to obtain more p53. Approximately two times more amount of p53 was found from the cells treated STZ and $TNF\alpha$ simultaneously compared to the cell treated $TNF\alpha$ alone. The p53 increment in the presence of STZ was not caused by the induction of p53 gene expression. When new production of p53 induced by the $TNF\alpha$ was inhibited by the treatment of cycloheximide, O-GlcNAc modification decreased and phosphorylation increased on pre-existing p53 after $TNF\alpha$ treatment. But in the presence of STZ and $TNF\alpha$ at the same time, more O-GlcNAcylation occurred on p53, The level of ubiquitination on p53 was also reduced in the presence of STZ. Approximately three times less amount of Mdm2 bound to this hyperglycosylated p53. From this result it might be concluded that treatment of STZ to inhibit O-GlcNAcase increased O-GlcNAc modification level on p53 and the increment of O-GlcNAc modification stabilized p53 from ubiquitin proteolysis system.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.12
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• pp.7561-7568
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• 2013

Galectin-3 (Gal-3) is a carbohydrate-binding protein which is thought to be involved in cancer progression but its contribution to epithelial ovarian cancer (EOC) remains unclear. The present study sought to determine the role of Gal-3 in chemoresistance of the human SKOV-3 ovarian cancer cell line to paclitaxel (PTX) using recombinant human Gal-3 (rhGal-3) and PectaSol-C modified citrus pectin (Pect-MCP) as a specific Gal-3 competitive inhibitor. Our results showed 41% increased cell proliferation, 36% decreased caspase-3 activity and 33.6% increased substrate-dependent adhesion in the presence of rhGal-3 compared to the control case (p<0.001). Treatment of cells with a non-effective dose of PTX (100nM) and 0.1% Pect-MCP in combination revealed synergistic cytotoxic effects with 75% reduced cell viability and subsequent 3.9-fold increase in caspase-3 activity. Moreover, there was 39% decrease in substrate-dependent adhesion compared to control (p<0.001). These results suggest that inhibition of Gal-3 could be a useful therapeutic tool for combination therapy of ovarian cancer.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2593-2598
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• 2011

Polyphenols (PPs) are known as antioxidant compounds having benign biological activities. In this paper, a series of hybrid molecules between the free or acetyl protected polyphenol compounds were synthesized and their in vitro antioxidant activity (DPPH assay) and cholinesterase [acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)] inhibition activities were evaluated. As expected, free phenolic hybrid compounds (6 and 8) showed better antioxidant activity than acetyl protected hybrid compounds (5 and 7) from DPPH assay. But the contrast result was obtained from BuChE inhibition assay. Acetyl protected hybrid compounds (5 and 7) showed better inhibition activity for BuChE than free phenolic hybrid compounds (6 and 8). Specifically, 10 (AcFA-AcFA) were shown as an effective inhibitor of BuChE ($IC_{50}=2.3{\pm}0.3{\mu}M$) and also had a great selectivity for BuChE over AChE (more than 170 fold). Inhibition kinetic studies with acetyl protected compounds (5, 7, 9, and 10) indicated that 5, 7 and 10 are a hyperbolic mixed-type inhibition and 10 is a competitive inhibition type. The binding affinity (Ki) value of 10 to BuChE is $2.32{\pm}0.15{\mu}M$.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2494-2504
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• 2014

P38 mitogen activated protein (MAP) kinase is an important anti-inflammatory drug target, which can be activated by responding to various stimuli such as stress and immune response. Based on the conformation of the conserved DFG loop (in or out), binding inhibitors are termed as type-I and II. Type-I inhibitors are ATP competitive, whereas type-II inhibitors bind in DFG-out conformation of allosteric pocket. It remains unclear that how these allosteric inhibitors stabilize the DFG-out conformation and interact. Organosilicon compounds provide unusual opportunity to enhance potency and diversity of drug molecules due to their low toxicity. However, very few examples have been reported to utilize this property. In this regard, we performed docking of an inhibitor (BIRB) and its silicon analog (Si-BIRB) in an allosteric binding pocket of p38. Further, molecular dynamics (MD) simulations were performed to study the dynamic behavior of the simulated complexes. The difference in the biological activity and mechanism of action of the simulated inhibitors could be explained based on the molecular mechanics/generalized Born surface area (MM/GBSA) binding free energy per residue decomposition. MM/GBSA showed that biological activities were related with calculated binding free energy of inhibitors. Analyses of the per-residue decomposed energy indicated that van der Waals and non-polar interactions were predominant in the ligand-protein interactions. Further, crucial residues identified for hydrogen bond, salt bridge and hydrophobic interactions were Tyr35, Lys53, Glu71, Leu74, Leu75, Ile84, Met109, Leu167, Asp168 and Phe169. Our results indicate that stronger hydrophobic interaction of Si-BIRB with the binding site residues could be responsible for its greater binding affinity compared with BIRB.

• Proceedings of the Ginseng society Conference
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• 1993.09a
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• pp.40-48
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• 1993

Intravenous administration of saponin extracted from the root of Panax ginseng lowered the blood pressure dose-dependently (10-200 mg/kg, B.W) in anesthetized rats. Therefore, experiments were designed to study the hypothesis that the lowering of blood pressure is associated with the release of endothelium-derived relaxing factor and the accumulation of guanosine 3, 5-cyclic monophosphate (cGMP). Rings of thoracic aorta with and without endothelium were suspended for the measurement of isometric tension in organ chamber and the tissue content of cGMP was measured by radioimmunoassay. All experiments were performed in the presence of $indomethacin(10^{-5}M).$ Ginseng saponin $(10^{-5}-3{\times}10^{-6}g/ml)$ relaxed contractions induced by phenylephrine $10^{-6}M)$ in the aorta with endothelium but not in that without endothelium. Treatment of aortic rings with $N^G$ monomethyl-L-arginine (L-NMMA, $10^{-4}M$ for 30 min), a competitive inhibitor of nitric oxide synthase, and methylene blue $(MB,\;3{\times}10^{-7}M$ for 30 min). an inhibitor of soluble guanylate cyclase, diminished the relaxation induced by Ginseng saponin. Ginseng saponin $10^{-4}g/ml$ for 2 min) increased the accumulation of cGMP in rings with endothelium. L-NMMA and MB inhibited the accumulation of cGMP induced by Ginseng saponin. These data suggest that vascular relaxations induced by Ginseng saponin are mediated by release of endothelium-derived relaxing factor and the accumulation of cGMP. The effect of Ginseng saponin on endothelial function in hypercholesterolemic rabbits was examined. In hypercholesterolemic rabbits fed with $2\%$ cholesterol for 8 weeks, relaxation of aortic rings to acetylcholine was impaired. The impaired relaxations of aortic rings in hypercholesterolemic rabbits were improved by dietary supplementation of Ginseng saponin, probably because of an improved release of endothelium - derived relaxing factor.