• Korean Journal of Microbiology
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• v.52 no.3
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• pp.278-285
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• 2016

The bifunctional PheA protein, having chorismate mutase and prephenate dehydratase (CMPD) activities, is one of the key regulatory enzymes in the aromatic amino acid biosynthesis in Escherichia coli, and is negatively regulated by an end-product, phenyalanine. Therefore, PheA protein has been thought as useful for protein engineering to utilize mass production of essential amino acid phenylalanine. To obtain feedback resistant PheA protein against phenylalanine, we mutated by using random mutagenesis, extensively screened, and obtained $pheA^{FBR}$ gene encoding a feedback resistant PheA protein. The mutant PheA protein contains substitution of Leu to Phe at the position of 118, displaying that higher affinity (about $290{\mu}M$) for prephenate in comparison with that (about $850{\mu}M$) of wild type PheA protein. Kinetic analysis showed that the saturation curve of $PheA^{FBR}$ against phenyalanine is hyperbolic rather than that of $PheA^{WT}$, which is sigmoidal, indicating that the L118F mutant enzyme has no cooperative effects in prephenate binding in the presence of phenylalanine. In vitro enzymatic assay showed that the mutant protein exhibited increased activity by above 3.5 folds compared to the wild type enzyme. Moreover, L118F mutant protein appeared insensitive to feedback inhibition with keeping 40% of enzymatic activity even in the presence of 10 mM phenylalanine at which the activity of wild type $PheA^{WT}$ was not observed. The substitution of Leu to Phe in CMPD may induce significant conformational change for this enzyme to acquire feedback resistance to end-product of the pathway by modulating kinetic properties.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.2
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• pp.107-117
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• 2004

If doubtlessly contributes much to agriculture and rural development. The roles can be summarized as; 1. to activate rural areas and to provide more comfortable and safe rural life with equivalent services to those in urban areas, facilitating distance education, tole-medicine, remote public services, remote entertainment etc. 2. To initiate new agricultural and rural business such as e-commerce, real estate business for satellite officies, rural tourism and virtual corporation of small-scale farms. 3. To support policy-making and evaluation on optimal farm production, disaster management, effective agro-environmental resource management etc., providing tools such as GIS. 4. To improve farm management and farming technologies by efficient farm management, risk management, effective information or knowledge transfer etc., realizing competitive and sustainable farming with safe products. 5. To provide systems and tools to secure food traceability and reliability that has been an emerging issue concerning farm products since serious contamination such as BSE and chicken flu was detected. 6. To take an important and key role for industrialization of farming or lam business enterprise, combining the above roles.

• Journal of Animal Science and Technology
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• v.46 no.4
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• pp.625-634
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• 2004

The objective of this experiment is to study the possibility of lactate dehydrogenase(LDH) enzyme to prevent lactate accumulation in the rumen, For understanding capacity of bacterial LDH in rumen environments, this study was conducted to explore the effects of temperature, pH, VFAs and metal ions on Lactobacillus sp. FFy111-1's LDH activity, and the LDH activation in rumen fluid accumulated lactate. The optimum pH and temperature of LDH were pH 7.5 and 40$^{\circ}C$, respectively. The LDH activity had a good thennostability at range from 30 to 50$^{\circ}C$. The highest pH stability of the enzyme was at ranges from pH 7.0 to 8.0 and the enzyme activities showed above 64% level of non-treated one at pH 6.0 and 6.5. The LDH was inactivated by VFAs treatments but was enhanced by metal ion treatments without NaCl and $CuSO_4$ Especially, the LDH activity was increased to 127% and 124% of its original activity by 2 mM of $BaCl_2$ and $MnSO_4$, addition, respectively. When the acidic rumen fluid was treated by LDH enzyme of Lactobacillus sp. FFy111-1, the lactate concentration in the rumen fluid was lower compared with non-treated rumen fluid(P<0.05). This lactate reduction was resulted from an action of LDH. It was proved by result of purified D,L-LDH addition that showed the lowest lactate concentration among the treatments(P<0.05). Although further investigation of microbial LDH and ruminal lactate is needed, these findings suggest that the bacterial LDH has the potential capability to decrease the lactate accumulated in an acidic rumen fluid. Also, screening of super LDH producing bacteria and technical development for improving enzyme activity in rumen environment are essential keys for practical application.

• Applied Biological Chemistry
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• v.41 no.2
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• pp.130-136
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• 1998

Microsomes of tomato roots were prepared and the activities of microsomal ATPases were measured in order to understand the molecular mechanisms of various ion transports. The activities of plasma membrane $H^+-ATPase$ and vacuolar $H^+-ATPase$ were evaluated to ${\sim}30%$ and ${\sim}38%$ of total microsomal ATPase activity by using their specific inhibitor, vanadate and nitrate $(NO^-_3)$, respectively. The inhibitory effects of vanadate and $NO^-_3$ were additive and the simultaneous additions of these two inhibitors decreased the total activity up to $50{\sim}70%$. The microsomal ATPase activity was regulated key pH and the maximal activity was obtained at pH 7.4. The activity of microsomal ATPase was increased by $K^+$ up to ${\sim}30%$ at the concentration of $K^+$ above 10 mM. However, the $K^+-induced$ increase in the activity was completely inhibited by the simultaneous addition of $Na^+$. To identify the ATPase activity regulated by $K^+$, the effects of specific inhibitors were measured. Vanadate and $NO^-_3$ inhibited total ATPase activity by 27% and 32% in the absence, of $K^+$ and by 27% and 40% in the presence of 120 mM $K^+$, respectively. These results suggest that $K^+$ increases the activity of $NO^-_3-sensitive$ vacuolar $H^+-ATPase$ but not that of vanadate-sensitive plasma membrane $H^+-ATPase$ since vanadate has no effect on $K^+-induced$ increase in ATPase activity. The microsomal ATPase activity was also decreased by increasing $Ca^{2+}$ concentration. Interestingly, $NO^-_3$ blocked the $Ca^{2+}-induced$ inhibition of microsomal ATPase activity; however, vanadate had no effect. These results imply that vacuolar $H^+-ATPase$ is activated by $K^+$ and inhibited by $Ca^{2+}$.

• Applied Biological Chemistry
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• v.37 no.3
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• pp.143-147
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• 1994

Four samples of commercially manufactured yogurts (plain, drinking type) were purchased and evaluated their physico-chemical properties, buffering capacity. And the survival rate of lactic acid bacteria and their ${\beta}-galactosidase$ activity under the acidic conditions (in vitro) were investigated. The values of pH, titratable acidity, viscosity and viable cell counts of yogurts were $3.71{\sim}4.08$, $0.990{\sim}1.045%$, $256{\sim}3164\;cps.$ and $10^8{\sim}10^9\;cfu/ml$, respectively. The volume of 1.0 M-HCl required to reduce the pH of yogurt (50 ml) to minus 2 value was $3.58{\sim}4.33\;ml$. When commercial yogurts were incubated at $37^{\circ}C$ for 120 minutes under the acidic conditions (pH 3.5, 2.5, 1.5), the survival rates of lactic acid bacteria in yogurt were $3.5{\times}10^{-2}{\sim}3.6{\times}10^{-1}%$ at pH 2.5, $8.3{\times}10^{-5}{\sim}4.2{\times}10^{-3}%$ at pH 1.5, respectively, but there was no significant difference at pH 3.5. The remaining activities of ${\beta}-galactosidase$ were $9.4{\sim}36.2%$ at pH 2.5, $4.2{\sim}19.0%$ at pH 1.5, respectively. These results suggested that a significant number of lactic acid bacteria in yogurt might be destroyed in the hostile environment of the stomach, but ${\beta}-galactosidase$ activity from yogurt might be somewhat maintained probably due to the protecting effect by its cell wall and membrane.

• Applied Biological Chemistry
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• v.49 no.2
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• pp.91-96
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• 2006

Antioxidant activities and biological properties such as antimutagenic and cytotoxic effect of Phellinus linteus extracts from different extraction conditions were measured against Salmonella typhimurium and human cancer cell lines. DPPH free radical scavenging activities of the extracts were higher in the solutions extracted with ethanol (17.14) and ethanol after water (17.79), respectively. In the Ames test, ethanol extract of P. linteus alone did not exhibit any mutagenicity but showed substantial inhibitory effect against mutations induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 4-nitroquinoline-1-oxide (4NQO), and benzo $({\alpha})$ pyrene $(B({\alpha})P)$. The extracts of ethanol and ethanol after water of P. linteus $(200\;{\mu}g/plate)$ had the highest inhibitory effect of 61.5 and 60.9%, respectively, on the mutagenesis on S. typhimurium TA98 strain induced by $B({\alpha})P$. Extracted solutions of ethanol and ethanol after water of P. linteus showed high antimutagenic effect against MNNG, 4NQO, Trp-P-1 and $B({\alpha})P$, causing mutations in S. typhimurium TA100 strain. The anticancer effects of P. linteus extracts were investigated against human fibrosarcoma HT-29 and human hepatocellular carcinoma HepG2. The treatment of 0.5 mg/ml of ethanol, ethanol after water and water extracts of P. linteus had the highest cytotoxicity of 59, 57, 54%, respectively against HT-27 cell line, whereas low cytotoxicity effects were observed against HepG2 cell line in the range of $10{\sim}30%$. The ethanol and water extracts of P. linteus also showed the nitrate scavenging ability at different pHs. The ethanol extract showed higher nitrate-scavenging ability compared to water extract of P. linteus.

• Applied Biological Chemistry
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• v.18 no.1
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• pp.10-15
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• 1975

These studies were conducted to induce the available mutants in Takju yeasts by the irradiation of UV light. Two original strains(5-Y-5, 6-Y-6) using for irradiation of UV selected from 24 strains which were isolated from the Takju mashes And Nuruks collected from 12 local regions of Chungnam and Chungbuk provinces in Korea, and the irradiations to the yeasts with UV light were carried out at a distance 10-40cm from the sources of irradiation for 10-220 seconds. The purpose of this experiment is to report the effects of irradiating distances and times of UV light on the survival ratio of orginal yeasts, and the identification of two orginal yeasts and three mutants induced by the irradiation of UV light. The results were summarized as follows. 1) The effects of irradiating distances and times on the survival ratio on the yeasts were represented as follows. and acid productivity to the survival strains by the irradiation of UV light. The selected mutants were the strains 30-24, 40-27 which have more powerful fermentability about 10 percent than those of original strains and a strain 30-81 which have potential acid productivity. 3) The selected yeasts (5-Y-5, 6-Y-6) were identified to Saccharomyces cerevisiae by a taxonomic study of Lodder and the mutants(30-81, 40-27, 30-81) induced from above yeasts by the irradiation of UV light have almost same properties two orginal yeasts in the identical characteristics.

• Applied Biological Chemistry
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• v.45 no.2
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• pp.92-96
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• 2002

Present contamination levels of soils along the major roadsides of Seoul, Korea were investigated, and base-line data were accumulated for future use. Topsoil $(1{\sim}5$ cm) and subsoil $(20{\sim}50$ cm) from five districts (Gangdong-, Gwangjin-, Nowon-, Seodaemun- and Seongdong-gu) were sampled. The collected samples were airdried, passed through 2-mm sieves, and analyzed to determine the physicochemical properties including pH, EC, CEC, exchangeable cations (Ca, Mg, K, and Na), and heavy metal contents (Cd, Cu, Pb, and Zn). Soil textures of topsoils and subsoils were mainly loamy sand and sandy loam, respectively. The range of pH was $4.5{\sim}10$.0 with an average of 7.5 for both topsoil and subsoil, which is much higher than that of the forest soils in Seoul. The ranges of 0.1 N HCI extractable Cd, Cu, Pb, and Zn contents for both topsoils and subsoils were $0.0l{\sim}l.19$, N.D. (not $detected){\sim}228$.99, $N.D.{\sim}352$.54, and $2.97{\sim}332$.96 mg $kg^{-1}$, respectively. Most of the average heavy metal contents were lower than the concern level of the Soil Environment Conservation Act of Korea, but were much higher than those of the , forest soils in Seoul. Some sites were higher in heavy metal contents than the concern levels; in particular, the average Cu content in Seongdong-gu was much higher than the concern level, 50 mg $kg^{-1}$. Careful management of the soil to prevent the aggravation of the present contamination level and the dissemination of contamination is highly recommended.

• Applied Biological Chemistry
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• v.47 no.4
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• pp.390-395
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• 2004

In order to characterize ion channels present in tomato roots, microsomes were incorporated into an artificial lipid bilayer arranged for electrophysiological analysis. Of the five different ion channels that could be found, a channel of 450 pS conductance was found most frequently. This channel displayed subconductance states of 450, 257 and 105 pS. All subconductance states showed linear current-voltage relationships. At positive holding potentials, high frequency of transient channel openings was observed; however, at negative potentials, the open times were long and open probability high. Po was 0.83 at -40 mV. When an additional 50 mM $K^+\;or\;Na^+$ was added to the cis side of bilayer, the reversal potentials shifted in the negative direction to near -10 mV. Thus, the 450 pS cation channel selects poorly between $K^+\;and\;Na^+$. In the presence of $100\;{\mu}M$ metal ions, the channel activity was severely inhibited by $La^{3+},\;Ba^{2+},\;and\;Zn^{2+}$, and Po was decreased to 0.2 or even less. However, $Al^{3+}\;and\;Cd^{2+}$ decreased the activity by only 20%. Interestingly, each metal ion showed different kinetics of channel inhibition. While $500\;{\mu}M\;La^{3+}$ inhibited the activities of all subconductance state, 1 mM $Zn^{2+}$ inhibited all except the 105 pS state. $Cd^{2+}$ changed the gating of the channel from a long-opening state to brief transient openings even at negative holding potentials. These data represent that the metal ions may have different binding sites on the channel protein and could be useful modulators and probes to investigate structural characteristics as well as the functional roles of the 450 pS channel on the root physiology.

• Journal of Dairy Science and Biotechnology
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• v.30 no.1
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• pp.23-30
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• 2012

This study was carried out to investigate the quality characteristics of yoghurt with varying contents of Sanmeoru (Vitis amurensis Ruprecht) wine (SW). Yoghurts were fermented with 2 kinds of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus; Yo-$MIX^{TM5}505$, Danisco, Denmark). The changes in quality characteristics were investigated during fermentation and storage, and anthocyanin composition was analyzed after fermentation. The pH decreased in all treatments, while titratable acidity and viscosity gradually increased during fermentation. The viscosity of the yoghurt with 5.0% cultured SW added was higher than in other groups. The viable counts of lactic acid bacteria gradually increased during fermentation. The sample of the 5.0% cultured SW-yoghurt was higher than that of the other groups. The pH slowly decreased during the storage period; this was lower in the control yoghurt than in the yoghurts containing SW, and the changes of titratable acidity in the samples containing 5.0% and 30.0% cultured SW were lower than that in the yoghurt containing 1.0% cultured SW and in the control. The change in viscosity and number of viable cells during storage was higher in the yoghurts containing SW than in the control group. The levels of anthocyanin increased with the SW content in the yoghurt. Sensory scores for taste of the yoghurt with 1.0% added SW was significantly higher than for the other groups. Yoghurt with added SW kept at $4^{\circ}C$ for 12 days retained its quality characteristics fairly well.