• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1217-1221
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• 2000

L-alanine dehydrogenase from Bacillus subtilis exhibits allosteric kinetic properties in the presence of $ZN^{2+}$. $ZN^{2+}$ induces the binding of substrate (L-alanine) to be cooperative at pH 8.0. The effect of pH variation between pH 7.0 and pH 10.0 on the inhibition by $ZN^{2+}$ correlates with the pH effect on the $K_m$ values for L-alanine within these pH range indicating that $ZN^{2+}$ and substrate compete for the same site. No such cooperativity is induced by $ZN^{2+}$ when the reaction is carried out at pH 10. At this higher pH, $ZN^{2+}$ binds with the enzyme with lower affinity and noncompetitive with respect to L-alanine. Inhibition of L-alanine dehydrogenase by $ZN^{2+}$ depends on the ionic strength. Increase in KCI concentration reduced the inhibition, but allosteric property in $ZN^{2+}$ binding is conserved. A model for the regulatory mechanism of L-alanine dehydrogenase as a noncooperative substrate-cooperative cofactor allosteric enzyme, which is compatible in both concerted and the sequential allosteric mechanism, is proposed.

• BMB Reports
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• 제35권2호
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• pp.220-227
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• 2002

Two aspartate aminoransferase (EC 2.6.1.1) isoenzymes (AAT-1 and AAT-2) from Lupinus albus L. cv Estoril were separated, purified, and characterized. The molecular weight, pI value, optimum pH, optimum temperature, and thermodynamic parameters for thermal inactivation of both isoenzymes were obtained. Studies of the kinetic mechanism, and the kinetics of product inhibition and high substrate concentration inhibition, were performed. The effect of some divalent ions and irreversible inhibitors on both AAT isoenzymes was also studied. Native PAGE showed a higher molecular weight for AAT-2 compared with AAT-1. AAT-1 appears to be more anionic than AAT-2, which was suggested by the anion exchange chromatography. SDS-PAGE showed a similar sub-unit molecular weight for both isoenzymes. The optimum pH (between 8,0 and 9.0) and temperature ($60-65^{\circ}C$) were similar for both isoenzymes. In the temperature range of $45-65^{\circ}C$, AAT-2 has higher thermostability than AAT-1. Both isoenzymes showed a high affinity for keto-acid substrates, as well as a higher affinity to aspartate than glutamate. Manganese ions induced an increase in both AAT isoenzymes activities, but no cooperative effect was detected. Among the inhibitors tested, hydroxylamine affected both isoenzymes activity by an irreversible inhibition mechanism.

• 대한약리학회지
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• 제27권2호
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• pp.145-153
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• 1991

염증성 질환의 원인 인자중 하나로 알려진 사람 호중구 Cathepsin G를 두단계의 크로마토그라피를 거쳐 분리하였다. 이 순수 분리된 효소를 이용하여 토끼에서 항체를 In Vivo 합성하고 그 혈액으로부터 순수 항체를 분리하였다. NSAIDs 약제중 phenylbutazone, sulindac, oxyphenbutazone, salicilic acid등은 이 효소를 강력하게 억제하였으며 $IC_{50}$은 $0.3{\sim}0.8\;mM$ 이었다. 고려인삼의 지용성분획도 tetracycline, novobiosin, rifamycin이 Cathepsin G의 효소 활성도에 대해서 강력한 억제 작용을 나타내었으나 다른 항생제는 그 작용이 무시할 수 있을 정도였다. 그러나 tetracycline계열의 항생제의 경우 실제 치료 효과를 나타내는 혈중농도에서 강한 억제 작용을 보였다. 특히 항균 작용과 관계하는 tetracycline의 4번 위치의 N-dimethy radical을 제거한 tetracycline은 감염군의 약제 저항성을 피할 수 있을 것으로 생각되므로 만성 염증성질환의 장기 치료에 이용될 수 있는 새로운 약제로써 제시한다.

• 대한임상전기생리학회지
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• 제8권1호
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• pp.7-13
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• 2010

Purpose : This study was performed as follows in order to investigate the effect of presynaptic inhibition mechanism using the transcutaneous electrical stimulation (TES) for global synkinesis (GS) on the post-stroke hemiplegic patients. Methods : The subjects consist of 38 post stroke hemiplegic patients; experiments were performed on thirty patients excluding eight. The experiment was performed on sham group, sensory level stimulation group, and motor level stimulation group for 20 minutes a day 5 times a week for 6 weeks total. We compared the differences in GS levels and walking ability. The measurements were carried out pre, immediated, post 10th, and 20th, for a total of four measurements. Results : The GS level using sEMG found significant differences between groups at the post 10th and post 20th in dorsiflexion, and post 20th in plantarflexion (p<0.05, p<0.01). The motor level group indicated more significant differences when the number of electrical stimulations increased. TUG and 10 m walking test indicated a significant difference at immediated, post 10th, and post 20th. The motor level group showed more significant decreasing tendency than the sensory level group. Conclusion: From these results, electrical stimulation using presynaptic inhibition mechanism of transcutaneous electrical stimulation (TES) had positive effects for walking ability on inhibition of muscle tone in lower extremity. The motor level stimulation group experienced a more significant effect than the sensory level stimulation group. Therefore, the transcutaneous electrical stimulation (TES) is considered to be effective on walking ability increasing through inhibition of muscle tone in lower extremity for rehabilitation of post stroke hemiplegic patients.

• Bulletin of the Korean Chemical Society
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• 제23권10호
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• pp.1371-1372
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• 2002

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.727-730
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• 1999

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.61-70
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• 2013

Corrosion inhibition of carbon steel in 2M HCl by some benzohydrazide derivatives (I-III) was studied using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques at $30^{\circ}C$. Polarization studies showed that all the investigated compounds are of mixed type inhibitors. Temperature studies revealed a decrease in efficiency with rise in temperature and corrosion activation energies increased in the presence of the hydrazide derivatives, probably implying that physical adsorption of cationic species may be responsible for the observed inhibition behavior. Electrochemical impedance studies showed that the presence of benzohydrazide derivatives decreases the double layer capacitance and increases the charge transfer resistance. The adsorption of these compounds on carbon steel surface was found to obey Temkin's adsorption isotherm. Synergistic effects increased the inhibition efficiency in the presence of halide additives namely KI and KBr. An inhibition mechanism was proposed in terms of strongly adsorption of inhibitor molecules on carbon steel surface.

• Journal of Microbiology and Biotechnology
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• 제13권3호
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• pp.332-337
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• 2003

Enzyme kinetics data play a vital role in the design of reactors and control of processes. In the present study, kinetic studies on pectinases were carried out. Partially purified polymethylgalacturonase (PMG) and polygalacturonase (PG) were the two pectinases studied. The plot of initial rate vs. initial substrate concentration did not follow the conventional Michaelis-Menten kinetics, but substrate inhibition was observed. For PMG, maximum rate was attained at an initial pectin concentration of 3 g/l, whereas maximum rate was attained when the initial substrate concentration of 2.5 g/l of polygalacturonic acid for PG I and PG II. The kinetic data were fitted to five different kinetic models to explain the substrate inhibition effect. Among the five models tested, the combined mechanism of protective diffusion limitation of both high and inhibitory substrate concentrations (semi-empirical model) explained the inhibition data with 96-99% confidence interval.

• 약학회지
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• 제44권3호
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• pp.272-278
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• 2000

The antiinflammatory mechanism of NSAIDs is attributed to the reduction of prostaglandin synthesis by the direct inhibition of cyclooxygenase. Inhibition of prostaglandin production in organs such as stomach and kidney can result in gastric lesions, nephrotoxicity and increased bleeding. In this study, newly designed COX-2 inhibitors, synthesized 1,2-benzothiazine derivatives, were screened in vitro for selectivity of COX-1 and COX-2 inhibition properties. Lead compounds in the structure-activity relationship were studied to synthesize new highly selective COX-2 inhibitors.13 determine inhibitory effect of COX-2, synthesized 1,2-benzothiazine derivatives were screened with accumulation of prostaglandin by lipopolysaccharide (LPS) in aspirin-treated macrophages and murine macropharge cell. Some of synthesized 1,2-benzothiazine derivatives were shown to be effective as selective COX-2 inhibitory activity. Others exhibited a preferential inhibition of COX-2, although some COX-1 inhibitory activity was still present. As a conclusion, simple monomer derivatives were more active than dimer derivatives. Substitution of halogen (Br, C1) on the benzothiazine nucleus slightly enhanced inhibition activity.

• 대한화학회지
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• 제57권2호
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• pp.264-271
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• 2013

Corrosion inhibition of mild steel used in water station in 35 ppm aluminum sulfate and 10 ppm chloride solution by Camellia sinensis leaves extract was studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques at $30^{\circ}C$. Results show that the inhibition efficiency increases with increasing concentration of the extract and decreases with increasing temperature. Inhibitive effect was afforded by adsorption of the extract's components which was found to accord with Langmuir adsorption isotherm. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency and was further corroborated by the values of activation parameters obtained from the experimental data.