• Journal of Life Science
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• v.28 no.3
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• pp.351-356
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• 2018

L-Serine dehydratase (LSD) is an iron-sulfur containing enzyme that catalyzes the conversion of L-serine to pyruvate and ammonia. Among the bacterial amino acid dehydratases, it appears that only the L-serine specific enzymes utilize an iron-sulfur cluster at their catalytic site. Moreover, bacterial LSDs are classified into four types based on structural characteristics and domain arrangement. To date, only the LSD enzymes from a few bacterial strains have been studied, but more detailed investigations are required to understand the catalytic mechanism of various bacterial LSDs. In this study, LSD type II from Mycobacterium tuberculosis (MtLSD) H37Rv was expressed and purified to elucidate the biochemical and catalytic properties using the enzyme kinetic method. The L-serine saturation curve of MtLSD exhibited a typically sigmoid character, indicating an allosteric cooperativity. The values of $K_m$ and $k_{cat}$ were estimated to be $59.35{\pm}1.23mM$ and $18.12{\pm}0.20s^{-1}$, respectively. Moreover, the plot of initial velocity versus D-serine concentration at fixed L-serine concentrations showed a non-linear hyperbola decay shape and exhibited a competitive inhibition for D-serine with an apparent $K_i$ value of $30.46{\pm}5.93mM$ and with no change in the $k_{cat}$ value. These results provide insightful biochemical information regarding the catalytic properties and the substrate specificity of MtLSD.

• Korean Journal of Cognitive Science
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• v.28 no.4
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• pp.329-347
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• 2017

Early research into category-based feature inference reported various phenomena in human thinking including typicality, diversity, similarity effects, etc. Later research discovered that participants' prior knowledge has an extensive influence on these sorts of reasoning. The current research tested the effects of causal knowledge on feature inference and conducted modeling on the results. Participants performed feature inference for categories consisted of four features where the features were connected either in common cause or common effect structure. The results showed typicality effects along with violations of causal Markov condition in common cause structure and causal discounting in common effect structure. To model the results, it was assumed that participants perform feature inference based on the difference between the probabilities of an exemplar with the target feature and an exemplar without the target feature (that is, $p(E_{F(X)}{\mid}Cat)-p(E_{F({\sim}X)}{\mid}Cat)$). Exemplar probabilities were computed based on causal model theory (Rehder, 2003) and applied to inference for target features. The results showed that the model predicts not only typicality effects but also violations of causal Markov condition and causal discounting observed in participants' data.

• Journal of Food Hygiene and Safety
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• v.23 no.3
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• pp.222-226
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• 2008

The purpose of this study was to investigate the preventive effects of Paeoniae Radix Extract(PRE) against the acute hepatotoxicity-inducing lipopolysaccharide(LPS) in the liver. PRE of 100 mg/kg concentration was intraperitoneally administered into rats at dose of 1.5 ml/kg for 20 days. On day 21, 5 mg/kg of LPS dissolved in saline was injected 4 hours before anesthetization. We examined the levels of glutamate oxaloacetate transaminase(GOT), glutamate pyruvate transaminase(GPT), lactate dehydrogenase(LDH) in serum of rats, superoxide dismutase(SOD) in mitochondrial fractions, and malondialdehyde(MDA), catalase(CAT), glutathione peroxidase(GPx) in liver homogenates. LPS-treatment markedly increased the levels of GOT, GPT, LDH and MDA, and significantly decreased those of SOD, CAT and GPx. But PRE-pretreatment decreased the levels of GOT, GPT, LDH and MDA, by 59.7%, 43.6%, 59.6% and 63.5%, respectively and increased those of SOD, CAT and GPx, by 85.5%, 57.8% and 62.9%, respectively. These results showed that the PRE had the preventive effects against the acute hepatotoxicity-inducing LPS in the liver.

• Journal of Veterinary Clinics
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• v.31 no.5
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• pp.449-453
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• 2014

A 2-year-old, intact male, Persian exotic cat, weighing 2 kg with a history of a palpated abdominal mass was admitted to Veterinary Medical Teaching Hospital, Seoul National University. On routine complete blood count (CBC) and serum biochemical analyses, there were anemia and 0.45 of albumin to globulin ratio. A feline infectious peritonitis (FIP) virus antibody test kit was negative. Radiography, ultrasonography and computed tomography (CT) were performed. A markedly enlarged abdominal mass was found. On cytologic examination of this mass, it was diagnosed as alimentary lymphoma or pyogranulomatous inflammation. Chemotherapeutic treatment for intestinal lymphoma was provided for several weeks, but the mass size was increased and clinical signs were not improved. The cat died six days after discontinuing chemotherapy. On postmortem examination, the definitive diagnosis was FIP. This case describes a cat with FIP in which an abdominal tumor had been suspected clinically.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.11
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• pp.1516-1521
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• 2009

This study was carried out to estimate beneficial effects of medicinal plant [Oenanthe javanica (MNR), Coicis lachryma-jobi L. var. (YM), Plantaginis asiatica L. (CJJ)] water extracts on activities of key enzymes such as lipoprotein lipase (LPL), acyl-CoA synthetase (ACS) and carnitine acetyltransferase (CAT) on lipid metabolism. LPL and ACS were extracted from the epididymal adipose tissue and liver of Zucker lean rats (lean) and Zucker fatty rats (fa/fa). MNR or YM water extract treatment significantly reduced the activity of lean and fa/fa LPL. When 10000 ppm of MNR, YM, and CJJ water extracts were tested, they decreased fa/fa LPL activity by 32.5%, 30.1% and 22.8%, respectively. The lean ACS activity was significantly higher in YM water extract treatment compared to the control and the MNR water extract treatment significantly increased the activity of fa/fa ACS, compared to the activity in the control (p<0.05). MNR water extract activated fa/fa ACS activity by 12-fold compared with control at 10000 ppm concentration. CAT activity was significantly higher in 10000 ppm and 20000 ppm CJJ water extract treatment than in the control. Thus, the MNR, YM and CJJ water extracts may have beneficial effects due to activities of enzymes related with fat metabolism in obese humans.

• Journal of Life Science
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• v.16 no.7 s.80
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• pp.1104-1108
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• 2006

The purpose of this study was to investigated the effects of Laminaria japonica fucoidan extract (LJFE) through the enzymatic regulation against the hepatotoxicity-inducing carbon tetrachloride $(CCl_4)$ in LJFE and $CCl_4-treated$ rats. LJFE of 100mg/kg concentration was intraperitoneally administered into rats at dose of 1.5m11kg for 14 days. On the day 15, 3.3ml/kg of $CCl_4$ dissolved in olive oil (1:1) was injected 12 hours before anesthetization. We examined the levels of glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) in serum of rats, superoxide dismutase(SOD) in mitochondrial fraction, and catalase(CAT), glutathione peroxidase(GPx) in liver homogenate. $CCl_4-treatment$ markedly increased the levels of GOT and GPT, and significantly decreased those of SOD, CAT and GPx. But LIFE pretreatment decreased the levels of GOT and GPT, by 40% and 64%, respectively and increased those of SOD, CAT and GPx, by 114%, 36.1% and 55.9%, respectively These results showed the LIFE had the enzymatic regulatory effects against the hepatotoxicity-inducing $CCl_4$ in the preventive way.

• Korean Journal of Plant Resources
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• v.24 no.1
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• pp.105-112
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• 2011

The objective of this study was to determine the effect of antioxidant enzyme activity and radical scavenging activities of thirteen kinds of natural plant pigments. The analytic method of antioxidant activities were measured by estimating DPPH free radical scavenging and nitrite scavenging ability activity. The free radical scavenging activity by method using stable free radical DPPH was the highest in the red cabbaged pigment. Addition of ethanol extract 1mg/ml from onion peel pigment displayed remarkable effect on nitrite scavenging ability about 91.9%. Antioxidative enzyme activity was evaluated in terms of superoxide dismutase(SOD), catalase(CAT), and ascorbate peroxidase(APX) activity. The bitter melon pigment had the highest SOD activity of 87.3%. The activities of CAT and APX were higher in the mulberry leave pigment compared with other natural plant pigments. In contrast, CAT activity of plant pigment samples were unaffected. These results suggest that natural plant pigment had the potent biological activities such as antioxidant enzyme activities, and that their activities exhibited differently depending on each kind of pigments.

• Journal of Marine Life Science
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• v.7 no.2
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• pp.171-179
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• 2022

The present study investigated the survival rate, respiration rate, plasma stress index, and histological changes according to exposure time of cultured red seabream (Pagrus major) and olive flounder (Paralichthys olivaceus) exposed to Cochlodinium polykrikoides red tide. Fish cultured in natural seawater were used as the control group. Cochlodinium polykrikoides density was set to 5,500±200 cells·ml^-1 in the experimental groups. All red seabreams died within 1 hour of exposure to red tide, whereas all olive flounders died within 5 hours of exposure. Analysis of physiological response revealed that in red seabream, plasma glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), catalase (CAT), and glutathione peroxidase (GPx) concentrations were increased; plasma glucose and superoxide dismutase (SOD) concentration were decreased. Meanwhile, in olive flounders, plasma cortisol, GOT, and GPT concentrations were increased; plasma glucose concentrations were increased during the first hour of exposure, followed by decrease after 5 hours; and plasma SOD, CAT, and GPx concentrations decreased during the first hour of exposure. Histological analysis revealed structural damage to the gills of both red seabream and olive flounder. In conclusion, the exposure of red seabream and olive flounder to Cochlodinium polykrikoides red tide at the density of 5,500 cells·ml^-1 induces oxidative stress, which activates antioxidant defense mechanisms, ultimately leading to liver and gill damage.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.238-245
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• 2024

The lactate electrode can be utilized either as an electrode for lactate sensor to monitor the patient's health status, stress level, and athlete's fatigue in real time or lactate fuel cell. In this study, we fabricated a high-performance electrode composed of lactate oxidase, catalase, and mitochondria, and investigated the surface analysis and electrochemical properties of this electrode. Carbon paper modified with single-walled carbon nanotubes (CP-SWCNT) had significantly improved electrical conductivity compared to before modification. The electrode to which lactate oxidase, catalase, and mitochondria were attached (CP-SWCNT-LOx-Cat-Mito) produced a higher current than the electrode to which lactate oxidase and catalase were attached. The amount of reduction current produced by the bilirubin oxidase (BOD)-attached electrode (CP-SWCNT-BOD) was greatly affected by the presence or absence of oxygen in the electrolyte. The fuel cell composed of CP-SWCNT-LOx-Cat-Mito (anode) and CP-SWCNT-BOD (cathode) produced maximum power (29 ㎼/cm²) at a discharge current density of 133 ㎂/cm². From this study, we had proved that mitochondria is essential for improving lactate sensor and fuel cell performance.

• Korean Journal of Medicinal Crop Science
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• v.13 no.6
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• pp.261-267
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• 2005

Alcohol metabolizing and antioxidant activity of Mentha species were investigated in rat liver. Fifty six Sprague Dawley rats were randomly divided into seven groups such as normal (ethanol excluded), negative control (40% ethanol (10 g/kg of body weight/day) fed), positive control (1 g Silymarin/kg of body weight/day with ethanol fed), two Mentha viridis extracts (0.2 g & 1 g M. viridis methanol ext./kg of body weight/day with ethanol fed) and two M piperita extracts (0.2 g & 1 g M. piperita methanol ext./kg of body weight/day with ethanol fed) groups. After 2 weeks, rats were sacrificed under ether. The activities of alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), catalase (CAT), manganese superoxide dismutase (Mn-SOD), glutathione peroxidase (GAH-px) and the content ofthiobarbituric acid reactive substance (TBARS) in the rat livers and the activity of glutamate pyruvate transferase (GPT) in serum were evaluated. From the analyses, 1 g M. viridis and 0.2 g M. piperita administrated groups showed higher ADH and ALDH activity than the other groups. Groups fed with 0.2 g and 1 g M. viridis ext. and 0.2 g M. piperita ext. showed higher CAT activity than the other groups. All the Mentha extract fed groups exhibited more effective in recovering Mn-SOD, GSH-px and GPT acitivities to a similar degree of normal group. TBARS contents of two M. viridis ext. fed group and 0.2 g M. piperita ext. fed group were higher than those of the other groups. M. viridis extract fed groups showed more effective in CAT and Mn-SOD activities than M. piperita extract groups at p < 0.05. Finally, it is concluded that both Mentha species have alcohol metabolizing and antioxidant activity and M viridis is more effective than M. piperita.