• Analytical Science and Technology
• /
• v.10 no.5
• /
• pp.378-385
• /
• 1997

In order to clarify the functional role of Tyr7 in human glutathione S-transferase P1-1, we extensively investigated the effect of mutation of Tyr7 on the substrate specificity and inhibition characteristics. The mutational replacement of Tyr7 with phenylalanine lowered the specific activities with 1,2-dichloro-4-nitrobenzene and 1,2-epoxy-3-(p-nitrophenoxy) propane for GSH-conjugation reaction to 3~5% of the values for the wild-type enzyme. The pKa of the thiol group of GSH bound in Y7F was about 2.4 pK units higher than that in the wild-type enzyme. The $I_{50}$ of hematin for Y7F was similar to that for the wild-type enzyme and those of benastatin A and S-(2,4-dinitrophenyl)glutathione were only moderately decreased. These results suggest that Tyr7 is considered to be important the catalytic activities not only for GSH-chloronitrobenzene derivatives but also for GSH-epoxide conjugation reaction, rather than to binding of the substrates.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.134.1-134
• /
• 2003

The purpose of this study was to investigate the release of p-hydroxybenzoic acid and other compounds from cell wall materials(CWM) and their cellulose fraction from carrot with chemical and enzymatic hydrolysis. To investigate this effect on cell wall chemistry of carrot, alcohol insoluble residue(AIR) of CWM were prepared and were extracted sequentially with water, imidazole, CDTA(-1, -2), Na$_2$CO$_3$(-1, -2), KOH(0.5, 1.0 and 4M), to leave a residue. These were analysed for their carbohydrate and phenolic acids composition. Arabinose and galactose were the main noncellulosic sugars. Phenolics esterified to cell walls in carrot were found to consist primarily of p-hydroxybenzoic acid with minor contribution from vanillin, ferulic acid and p-hydroxybenzaldehyde. p-Hydroxybenzoic acid was quite strongly bound to the cell wall. The contents of p-hydroxybenzoic acid in 0.5M KOH, Na$_2$CO$_3$-2, IM KOH, and ${\alpha}$-cellulose were 2,097, 1,360, 1,140, and 717 $\mu\textrm{g}$/g AIR from CWM, respectively. Alkali labile unknown aromatic compound(C$\sub$7/H$\sub$10/O$_2$) was found in ${\alpha}$ -cellulose hydrolyzate digested with driselase and cellulase. This compound was also found in hydrolyzate of 2 M trifluoroacetic acid at 120$^{\circ}C$ for 2 hours. Driselase treatment solubilized only 46.6 $\mu\textrm{g}$/g of the p-hydroxybenzoic acid from carrot AIR. These results indicate that p-hydroxybenzoic acid was associated with neutral polysaccharides, long chain galactose and branched arabinan from graded alcohol precipitation.

• Proceeding of EDISON Challenge
• /
• 2015.03a
• /
• pp.14-23
• /
• 2015

Alzheimer's disease is one of the most common types of degenerative dementia. As a considerable cause of Alzheimer's disease, neurotoxic plaques composed of 39 to 42 residue-long amyloid beta($A{\beta}$) fibrils have been found in the patient's brain in large quantity. A previous study found that erythrosine B (ER), a red color food dye approved by FDA, inhibits the formation of amyloid beta fibril structures. Here, in an attempt to elucidate the inhibition mechanism, we performed molecular dynamics simulations to demonstrate the conformational change of $A{\beta}40$ induced by 2 ERs in atomistic detail. During the simulation, the ERs bound to the surfaces of both N-terminus and C-terminus regions of $A{\beta}40$ rapidly. The observed stacking of the ERs and the aromatic side chains near the N-terminus region suggests a possible inhibition mechanism in which disturbing the inter-chain stacking of PHEs destabilizes beta-sheet enriched in amyloid beta fibrils. The bound ERs block water molecules and thereby help stabilizing alpha helical structure at the main chain of C-terminus and interrupt the formation of the salt-bridge ASP23-LYS28 at the same time. Our findings can help better understanding of the current and upcoming treatment studies for Alzheimer's disease by suggesting inhibition mechanism of ER on the conformational transition of $A{\beta}40$ at the molecular level.

• BMB Reports
• /
• v.40 no.2
• /
• pp.261-269
• /
• 2007

The structure and dynamics of a 37-residue antimicrobial peptide gaegurin 4 (GGN4) isolated from the skin of the native Korean frog, Rana rugosa, was determined in SDS micelles by NMR spectroscopy. The solution structure of the peptide in SDS micelles was determined from 352 NOE-derived distance constraints and 22 backbone torsion angle constraints. Dynamic properties for the amide backbone were characterized by $^1H-^{15}N $heteronuclear NOE experiments. The structural study revealed two amphipathic helices spanning residues 2-10 and 16-32 and that the helices were connected by a flexible loop. An intraresidue disulfide bridge was formed between residues Cys31 and Cys37 near the C-terminus. The loop region (11-15) connecting the two helices are were slightly more flexible than these helices themselves. From the fact that since there is no contact NOEs between two helices, it is implied that the GGN4 peptide shows an independent motion of both helices which has an angle of about $ 60^{\circ}-120^{\circ}$ from each other.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2003.05a
• /
• pp.17-17
• /
• 2003

tRNA (m¹ G37) methyltransferase (TrmD) catalyze s the trans for of a methyl group from S-adenosyl-L-methionine (AdoMet) to G/sup 37/ within a subset of bacterial tRNA species, which have a residue G at 36th position. The modified guanosine is adjacent to and 3' of the anticodon and is essential for the maintenance of the correct reading frame during translation. We have determined the first crystal structure of TrmD from Haemophilus influenzae, as a binary complex with either AdoMet or S-adenosyl-L-homocysteine (AdoHcy), as a ternary complex with AdoHcy/phosphate, and as an apo form. The structure indicates that TrmD functions as a dimer (Figure 1). It also suggests the binding mode of G/sup 36/G/sup 37/ in the active site of TrmD and catalytic mechanism. The N-terminal domain has a trefoil knot, in which AdoMet or AdoHcy is bound in a novel, bent conformation. The C-terminal domain shows a structural similarity to DNA binding domain of trp or tot repressor. We propose a plausible model for the TrmD₂-tRNA₂ complex, which provides insights into recognition of the general tRNA structure by TrmD (Figure 2).

• Molecules and Cells
• /
• v.37 no.1
• /
• pp.43-50
• /
• 2014

Jumonji domain-containing proteins (JMJD) catalyze the oxidative demethylation of a methylated lysine residue of histones by using $O_2$, ${\alpha}$-ketoglutarate, vitamin C, and Fe(II). Several JMJDs are induced by hypoxic stress to compensate their presumed reduction in catalytic activity under hypoxia. In this study, we showed that an H3K27me3 specific histone demethylase, JMJD3 was induced by hypoxia-inducible factor (HIF)-$1{\alpha}/{\beta}$ under hypoxia and that treatment with Clioquinol, a HIF-$1{\alpha}$ activator, increased JMJD3 expression even under normoxia. Chromatin immunoprecipitation (ChIP) analyses showed that both HIF-$1{\alpha}$ and its dimerization partner HIF-$1{\beta}$/Arnt occupied the first intron region of the mouse JMJD3 gene, whereas the HIF-$1{\alpha}/{\beta}$ heterodimer bound to the upstream region of the human JMJD3, indicating that human and mouse JMJD3 have hypoxia-responsive regulatory regions in different locations. This study shows that both mouse and human JMJD3 are induced by HIF-1.

• Korean Journal of Soil Science and Fertilizer
• /
• v.28 no.3
• /
• pp.207-217
• /
• 1995

Extracting efficiencies of seven extracting solutions currently employed in extracting heavy metals from soils were compared and the functional relationships among them were calculated by regression analysis for Cd, Zn, Cu, and Pb. Extracting solutions employed were 0.1M HCl, 0.1M $HNO_3$, 0.05M EDTA, 0.001M DTPA(pH 7.3), 1M $NH_4OAc$ (pH 7.0), 0.1M $NH_4Ox$, and 4M $HNO_3$ respectively. Soil samples were collected from rice paddy fields near old zinc mining sites and from rice paddy fields near agro-industry complexes. Soils sampled from old zinc mining sites were also extracted using a sequential extraction method. Extraction by 4M $HNO_3$ and sequential extraction were performed on the samples collected both in 1979 and in 1991 to investigate the change in content and in chemical form of heavy metals. Functional relationships among the extracting solutions were highly correlated for Cd and Zn, whereas those for Cu and Pb were not. The predominant chemical form of Cd. Zn, Cu, and Pb in soils from old zinc mining sites was found to be of sulfide/residue form. The exchangeable form of Cd, the organically bound form of Cu, and the carbonate form of Pb were relatively high, while the sulfide/residue form of Zn was very high(> 79%). Although transformation among the extracted forms was not clear during those 12 years, a decrease in total content of Cd, Zn, Cu, and Pb was clearly observed.

• The Korean Journal of Pesticide Science
• /
• v.2 no.3
• /
• pp.96-106
• /
• 1998

Rice plants were grown for 42 days in the specially made micro-ecosystem(pot) containing two different soils treated with fresh and 60-day-aged residues of [$^{14}C$]quinclorac, respectively, to elucidate the behaviour of the herbicide quinclorac residues in the soils. Amounts of $^{14}CO_{2}$ evolved from two soils treated with different residues with and without vegetation were all less than 2.2% of the total $^{14}C$, indicating that there was little microbial degradation of quinclorac in soil. $^{14}C$-Radioactivity absorbed and translocated into rice plants from soil A and B containing fresh quinclorac residues was 8.4 and 24.2%, respectively, of the originally applied $^{14}C$, while 5.5 and 17.7%, in aged residue soils. These results indicate that larger amounts of $^{14}C$ were absorbed by rice plants from soil B with less organic matter and clay than soil A, and the uptake of [$^{14}C$]quinclorac and its degradation products decreased with aging in soil. After 42 days of rice growing, 84.5 and 61.8% of the $^{14}C$ applied freshly to soil A and B, respectively, remained in soil, whereas, in the case of aged soils, 86.3 and 67.7% of the $^{14}C$ applied did. Meanwhile, without vegetation, more than 98.3% of the $^{14}C$ applied, in both fresh and aged residues, remained in soil, suggesting that quinclorac was relatively persistent chemically and microbiologically. Most of the non-extractable soil-bound residues of [$^{14}C$]quinclorac were incorporated into the organic matter and largely distributed in the fulvic acid portion.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.302-306
• /
• 2013

We report the dietary exposure to rotenone in the Korean population and children (1-18) through consumption of lettuce and cucumber. To obtain the residue data, we analyzed using the GC-NPD and HPLC-DAD method. Rotenone residues in samples were as follows; lettuce 0.16-1.15, cucumber < 0.001-0.006. The average dietary intake was determined using result from the 2009 Korea National Health and Nutrition Examination Survey Data. The risk index (RI) was calculated using rotenone residues and dietary intakes. The lettuce and cucumber showed the highest at 18.41%, 0.00, respectively. RI fell below 100 of %RfD showing no risks in these vegetables. Therefore, the risk assessment on the detected rotenone was evaluated as safe level.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.8
• /
• pp.1255-1261
• /
• 2006

An alkaliphilic bacterium, Bacillus sp. strain BK, was found to produce extracellular cellulase-free xylanolytic enzymes with xylan-binding activity. Since the pellet-bound xylanase is eluted with 2% TEA from the pellet of the culture, they contain a xylan-binding region that is stronger than the xylan-binding xylanase of the extracellular enzyme. The xylanases had a different molecular weight and xylan-binding ability. The enzyme activity of xylanase in the extracellular fraction was 6 times higher than in the pellet-bound enzyme. Among the enzymes, xylanase had the highest enzyme activity. When Bacillus sp. strain BK was grown in pH 10.5 alkaline medium containing xylan as the sole carbon source, the bacterium produced xylanase, arabinofuranosidase, acetyl esterase, and $\beta$-xylosidase with specific activities of 1.23, 0.11, 0.06, and 0.04 unit per mg of protein, respectively. However, there was no cellulase activity detected in the crude enzyme preparation. The hydrolysis of agricultural residues and kraft pulps by the xylanolytic enzymes was examined at 50$^{\circ}C$ and pH 7.0. The rate of xylan hydrolysis in com hull was higher than those of sugarcane bagasse, rice straw, com cop, rice husk, and rice bran. In contrast, the rate of xylan hydrolysis in sugarcane pulp was 2.01 and 3.52 times higher than those of eucalyptus and pine pulp, respectively. In conclusion, this enzyme can be used to hydrolyze xylan in agricultural residues and kraft pulps to breach and regenerate paper from recycled environmental resources.