• Journal of Life Science
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• v.14 no.2
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• pp.309-314
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• 2004

Cyclic AMP receptor protein (CRP) is involved in the transcriptional regulation of more than 100 genes in E. coli. CRP dimer is converted into active form via the sequential conformation change of cAMP binding pocket, hinge region and HTH DNA binding motif by binding of cAMP. The temperature gradient gel electrophoresis (TGGE) was applied to CRP protein to know whether it was an efficient technique to study the conformational transitions and the thermal stability. TGGE showed the unfolding process of wild-type and S83G CRP proteins with the temperature gradient set from 29 to 71$^{\circ}C$ on nondenaturing polyacrylamide gel. Melting temperature (Tm) was 57$\pm$1 and 55$\pm$1$^{\circ}C$ for wild-type and S83G CRP, respectively in acidic buffer[89.8 mM Glycine and 24 mM Boric acid (pH 5.8)].

• Proceedings of the Botanical Society of Korea Conference
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• 1999.07a
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• pp.57-62
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• 1999

Light-regulated translation of chloroplast mRNAs requires nuclear-encoded trans-acting factors that interact with the 5' untranslated region (UTR) of these mRNAs. A set of four proteins (60, 55, 47, and 38 kDa) that bind to the 5'-UTR of the psbA mRNA had been identified in C. reinhardtii. 47 kDa protein (RB47) was found to encode a chloroplast poly (A)-binding protein (cPABP) that specifically binds to the 5'-UTR of the psbA mRNA, and essential for translation of this mRNA, cDNA encoding 60 kDa protein (RB60) was isolated, and the amino acid sequence of the encoded protein was highly homologous to plants and mammalian protein disulfide isomerases (PDI), normally found in the endoplasmic reticulum (ER). Immunoblot analysis of C. reinhardtii proteins showed that anti-PDI recognized a distinct protein of 56 kDa in whole cell extract, whereas anti-rRB60 detected a 60 kDa protein. The ER-PDI was not retained on heparin-agarose resin whereas RB60 was retained. In vitro translation products of the RB60 cDNA can be transported into C. reinhardtii chloroplast in vitro. Immunoblot analysis of isolated pea chloroplasts indicated that higher plant also possess a RB60 homolog. In vitro RNA-binding studies showed that RB60 modulates the binding of cPABP to the 5'-UTR of the psbA mRNA by reversibly changing the redox status of cPABP using redox potential or ADP-dependent phosphorylation. Site-directed mutagenesis of -CGHC- catalytic site in thioredoxin-like domain of RB60 is an unique PDI located in the chloroplast of C. reinhardtii, and suggest that the chloroplast PDI may have evolved to utilize the redox-regulated thioredoxin like domain as a mechanism for regulating the light-activated translation of the psbA mRNA.

• Korean Journal of Clinical Pharmacy
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• v.8 no.1
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• pp.29-34
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• 1998

Murine CD38 is a 42 kDa type II glycoprotein expressed on cell surface of both B and T lymphocytes. CD38 is a multifunctional enzyme that catalyzes the formation and hydrolysis of cyclic adenosine diphosphoribose (cADPR): ADP-ribosyl cyclase activity of CD38 catalyzes the formation of cADPR from NAD and cADPR hydrolase activity of CD38 catalyzes the hydrolysis of cADPR to ADP-ribose (ADPR). And also, CD38 has the catalytic activity of NAD glycohydrolase (NADase) which catalyzes the hydrolysis of catalyzes the formation and hydrolysis of cyclic adenosine diphosphoribose (cADPR): ADP-ribosyl cyclase activity of CD38 catalyzes the formation of cADPR from NAD to ADPR. In this study, we attempted to purify CD38 from mouse lymphocytes by using the immobilized anti-CD38 monoclonal antibody. The single step immuno-affinity column chromatography resulted in homogeneous purification, showing a single protein of 42 kDa on a SDS polyacrylamide gel. We have investigated the effects of various inhibitors on the enzyme activities of the purified CD38. Cibacron blue (0.5 mM) inhibited all three enzyme activities of CD38, NADase, ADP-ribosyl cyclase and cADPR hydrolase activities. ADPR (2 mM) showed inhibitory effect on both cADPR hydrolase activity and NADase, but not on ADP-ribosyl cyclase activity. However, ATP (2 mM) inhibited only cADPR hydrolase activity. $Zn^{2+}$ (1 mM) showed similar inhibitory effect as that of ADPR, but activated cyclase activity These results suggest that CD38 has three different catalytic activity domains which might be differentially regulated by their specific inhibitors.

• Korean Journal of Microbiology
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• v.32 no.2
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• pp.155-162
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• 1994

Cells of Acinetobacter sp. strain JC1 DSM 3803, an aerobic monoxide-oxidizing bacterium, growing on glucose exhibited high catalase activity at the mid-exponential growth phase. The enzyme activity decreased gradually after then until the early stationary phase, increased again at the mid-stationary phase, and then decreased again thereafter. Cells growing on glucose was found to contain three kinds of catalses. Cat1, Cat2 and Cat3. The activities of Cat1 and Cat3 did change significantly during growth, but that of Cat2 exhibited significant variation. Cat3 was found to present only in cells growing on glucose, but not in cells growing on carbon monoxide of methanol. The activities of call and Cat3 in cell-free extracts were stable upon treatment with ethanol and chloroform, but decreased to some extent when the enzymewere treated with 2mM $H_2O_2$ and/or 3-amino-1,2,4-triazole (AT). Cat2 was found to be extremely sensitive to the ethanol-chloroform and $H_2O_2$ treatments, but was insensitive to the AT treatment. Cat1 exhibited enzyme activity after incubation for 1 min at 80$^{\circ}C$. Cat2 and Cat3 did not show enzyme activity after incubation for 1 min at 60$^{\circ}C$ and 70$^{\circ}C$, respectively. Cat2 was found to have peroxidase activity. Cat3 was purified to homogenity in seven steps. The molecular weight of the native enzyme was estimated to be 150,000. Sodium dodecyl sulfate-gel electrophoresis revealed two identical subunits of molecular weight 65,000. The enzyme was found to show two $K_m$ values of 39 mM and 58mM. The optimal pH for the enzyme activity was 7.0, but the activities at pH 6.0, 8.0, and 9.0, were found to be comparable to that at the optimal pH. The optimal temperature for the enzyme activity was found to be 40$^{\circ}C$. The enzyme also exhibited strong activity at 20$^{\circ}C$, 30$^{\circ}C$, and 50$^{\circ}C$. The purified enzyme was not affected by the ethanol-chloroform treatment. The enzyme, howerver, showed less than 10% of the original activity when it was treated with 12 mN AT, 0.1 mM $NaN_3$ of 1mM KCN.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.205-210
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• 1983

Extracellular $\beta$-galactosidase was prepared from a culture of Lactobacillus sporogenes, a spore-forming lactic acid bacterium. The enzyme functioned optimally at pH 6.8 and at 6$0^{\circ}C$ o-nitrophenyl-$\beta$-D-galactopyranoside (ONPG) in 0.05M sodium phosphate buffer. The activation energy of the enzymatic hydrolysis of ONPG was about 16,000 cal/mole below $50^{\circ}C$ and 11,300 cal/mole above the temperature. It was fairly stable over a pH range from 4.0 to 8.0 losing only less than 30% of its activity after hearting at 6$0^{\circ}C$ and pH 6.8 for 3 hours. Metal ions showed no significant effect on the enzyme activity, whereas L-cysteine exerted a slight stimulatory effect at the concentration of 10mM. The km values were 1.48mM for ONPG and 64.5mM for lactose. Hydrolysis of ONPG by the enzyme was product-inhibited by galactose (Ki=13.3mM, competitive inhibition) and by glucose(Ki= 11.4mM, uncompetitive type). The enzyme activity was also noncompetitively inhibited in the presence of lactose (Ki= 17.8mM).

• Applied Biological Chemistry
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• v.34 no.1
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• pp.49-53
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• 1991

Three polyphenol oxidase(polyphenol oxidase I, II and III ) were isolated from the crude extract of a Spuriopimpinella bracycarpa by $(NH_4)_2SO_4$ precipitation and subsequent Sephadex G-150 chromatography. The final preparation thus obtained showed three peaks of enzyme activity. Optimum pH and temperature for the activity of polyphenol oxidase were 7.5 and $30^{\circ}C$, respectively. The enzyme was completely inactivated when i4 was treated at$70^{\circ}C$ for 30min and at $80^{\circ}C$ for 5min at pH 6.5. The enzyme was partially inactivated by ascorbic acid, glutathione and potassium cyanide (0.1mM), and was completely inhibited by L-cysteine, ascorbic acid, glutathione and potassium cyanide(0.5 and 1.0mM). The enzyme has good activity on catechol and 3,4-dihydroxytoluene but was strongly inactivated on pyrogallol, dopamine and DL-dopa. The Michaelis cons4ant of the enzyme was 86.5mM with catechol as a substrate.

• Korean Journal of Food Science and Technology
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• v.26 no.1
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• pp.1-5
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• 1994

Effective thermal conductivity of rice starch was measured by the probe method. The thermal conductivity increased from $0.065{\sim}0.09\;W/mK$ to $0.13{\sim}0.23\;W/mK$ as the moisture content increased from 0 to 28.2%. At constant bulk density, the temperature effect on the thermal conductivity was positive and getting larger as the moisture content increased. In the moisture range $7.2{\sim}33.6%$, a very weak peak was found at $65^{\circ}C$ in DSC thermogram. Positive effect of interaction between temperature and moisture content on the thermal conductivity was thought to be due to the increase of thermal conductivity of water with temperature, not to starch gelatinization phenomenon. A regression equation $(r^{2}=0.963)$, Ke=-0.111+0.000203 T+0.00173 M.C.+0.000247 $P_{b}+0.000035$ M.C. T, was obtained in the range of moisture content (M.C.) of $0{\sim}28.2%$ (w.b.), temperature (T) of $25{\sim}70^{\circ}C$ and the bulk density $(P_{b})$ of $650{\sim}800\;kg/m^{3}$

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.44-56
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• 1996

CuInTe2 synthesised in a horizontal electric furnace was found to be polycrystalline. Single crystals of CuInTe2 were grown with the vertical Bridgman technique. The structure, Hall effect of the crystals were measured in the temperature range 30 to 293K. Both the polycrystals and single crystals of CuInTe2 were tetragonal in structure. The lattice constants of the polycrytals were measured as a=6.168Å and c=12.499Å, with c/a=2.026, these of the single crystals were measured as a=6.186Å and c=12.453Å, with c/a=2.013. The growth plane of the oriented single crystals was confirmed to be a (112) plane from the back-reflection Laue patterns. The Hall effect of the CuInTe2 single crystals was measured with the method of van der Pauw The Hall data of the samples measured at room temperature showed a carrier concentration of 2.14×1023holes/m3, a conductivity of 739.58Ω-1m-1, and a mobility of 2.16×10 -2m 2/V·s for the sample perpendicular to the c-axis. Values of 1.51×1023holes/m3, 717.55Ω-1m-1, and 2.97×10-2 m2/V·s were obtained for the sample parallel to the c-axis. The Hall coefficients for the samples both perpendicular and parallel to the c-axis in the temperature range 30K to 293K were always positive values. Thus the CuInTe2 single crystal was determined to be a p-type semiconductor.

• Nutrition Research and Practice
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• v.5 no.5
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• pp.396-403
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• 2011

Ceramides (Cer) comprise the major constituent of sphingolipids in the epidermis and are known to play diverse roles in the outermost layers of the skin including water retention and provision of a physical barrier. In addition, they can be hydrolyzed into free sphingoid bases such as $C_{18}$ sphingosine (SO) and $C_{18}$ sphinganine (SA) or can be further metabolized to $C_{18}$ So-1-phosphate (S1P) and $C_{18}$ Sa-1-phosphate (Sa1P) in keratinocytes. The significance of ceramide metabolites emerged from studies reporting altered levels of SO and SA in skin disorders and the role of S1P and Sa1P as signaling lipids. However, the overall metabolism of sphingoid bases and their phosphates during keratinocyte differentiation remains not fully understood. Therefore, in this study, we analyzed these Cer metabolites in the process of keratinocyte differentiation. Three distinct keratinocyte differentiation stages were prepared using 0.07 mM calcium (Ca$^{2+}$) (proliferation stage), 1.2 mM Ca$^{2+}$ (early differentiation stage) in serum-free medium, or serum-containing medium with vitamin C (50 ${\mu}L$/mL) (late differentiation stage). Serum-containing medium was also used to determine whether vitamin C increases the concentrations of sphingoid bases and their phosphates. The production of sphingoid bases and their phosphates after hydrolysis by alkaline phosphatase was determined using high-performance liquid chromatography. Compared to cells treated with 0.07 mM Ca$^{2+}$, levels of SO, SA, S1P, and SA1P were not altered after treatment with 1.2 mM Ca$^{2+}$. However, in keratinocytes cultured in serum-containing medium with vitamin C, levels of SO, SA, S1P, and SA1P were dramatically higher than those in 0.07- and l.2-mM Ca$^{2+}$-treated cells; however, compared to serum-containing medium alone, vitamin C did not significantly enhance their production. Taken together, we demonstrate that late differentiation induced by vitamin C and serum was accompanied by dramatic increases in the concentration of sphingoid bases and their phosphates, although vitamin C alone had no effect on their production.

• Korean Journal of Microbiology
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• v.40 no.3
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• pp.199-204
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• 2004

The parathion hydrolase (OPH) produced by Pseudomonas rhodesiae H5 was purified by ammonium sulfate precipitation, DEAE-Toyopearl 650M ion exchange chromatography and Sephadex gel filtration chromatography. Parathion hydrolase from crude extracts of P. rhodesiae H5 has two components designated as OPH $I_1$ and OPH $I_2$, Optimum pH and temperature of OPH $I_1$and OPH $I_2$ were pH 7.2 and $30^{\circ}C$, and pH 7.6 and $37^{\circ}C$, respectively. The activation energy of OPH $I_1$ for the hydrolysis of parathion was 3.01 ㎉/I, II, III in the temperature range of $4^{\circ}C$ to $30^{\circ}C$, and Michaelis constant ($K_m$) for parathion was 69.2 ${\mu}M$. The activation energy of OPH $I_2$ for the hydrolysis of parathion was 4.07㎉/㏖ in the temperature range of $4^{\circ}C$ to $37^{\circ}C$, and Michaelis constant for parathion was 150.9${\mu}M$. Furthermore OPH $I_1$ was completely inhibited by 1 mM $Ca^2+$, $Cu^2+$, $Mg^2+$, $Ni^2+$, but OPH $I_2$ was less inhibited than OPH $I_1$ by the metals used in this study.