• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1499-1502
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• 2004

An amperometric biosensor based on carbon paste electrodes (CPEs) for the determination of urea was constructed by enzyme (urease/GL-DH)-modified method. Urea was hydrolyzed to ${NH_4}^+$ by catalyzing urease onto the enzyme-modified electrode surface in sample solution. In the presence of ${\alpha}$-ketoglutarate and reduced nicotinamide adenine dinucleotide(NADH), a liberated ${NH_4}^+$ produce to L-glutamate and $NAD^+$ by Lglutamate dehydrogenase (GL-DH). After the chemical reaction was proceeded, the electrochemical reaction was occurred that an excess of the NADH was oxidized to $NAD^+$. The oxidation current of NADH was monitored at +1.10 volt vs. Ag/AgCl. An optimum conditions of biosensor were investigated: The optimum pH range for catalyzed hydrolysis reaction of urea was pH 7.0-7.4. The linear response range and detection limit were $2.0\;{\times}\;10^{-5}{\sim}2.0\;{\times}\;10^{-4}M\;and\;5.0\;{\times}\;10^{-6}M$, respectively. Another physiological species did not interfere, except L-ascorbic acid.

• Journal of Microbiology and Biotechnology
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• v.18 no.4
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• pp.663-669
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• 2008

The solvent-tolerant bacterium Enterobacter sp. VKGH12 is capable of utilizing n-butanol and contains an $NAD^+$-dependent n-butanol dehydrogenase (BDH). The BDH from n-butanol-grown Enterobacter sp. was purified from a cell-free extract (soluble fraction) to near homogeneity using a 3-step procedure. The BDH was purified 15.37-fold with a recovery of only 10.51, and the molecular mass estimated to be 38 kDa. The apparent Michaelis-Menten constant ($K_m$) for the BDH was found to be 4 mM with respect to n-butanol. The BDH also had a broad range of substrate specificity, including primary alcohols, secondary alcohols, and aromatic alcohols, and exhibited an optimal activity at pH 9.0 and $40^{\circ}C$. Among the metal ions studied, $Mg^{2+}$ and $Mn^{2+}$ had no effect, whereas $Cu^{2+},\;Zn^{2+}$, and $Fe^{2+}$ at 1 mM completely inhibited the BDH activity. The BDH activity was not inhibited by PMSF, suggesting that serine is not involved in the catalytic site. The known metal ion chelator EDTA had no effect on the BDH activity. Thus, in addition to its physiological significance, some features of the enzyme, such as its activity at an alkaline pH and broad range of substrate specificity, including primary and secondary alcohols, are attractive for application to the enzymatic conversion of alcohols.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.385-390
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• 2009

To investigate the cellular growth traits of a photosynthetic green algae, Chlorella pyrenoidosa, several tests upon a culture temperature, a culture time, the influence of nutrient and the intensity of illumination were executed. Using growth chamber, some optimal conditions for the culture of algae were as follows: The culture temperature was about $28^{\circ}C$, the culture time about 4 days, and the cellular growth of algae was in proportioned to the concentration of nutrient such as nutrient broth. And the more the intensity of illumination was increased, the more the algal cell showed good growth. And then, the activity of enzyme degrading acetaldehyde was also studied using HPLC from the same strain. This enzyme was dependent on $\beta$-$NAD^+$. And showed its optimal pH around on 9.0, and also its optimal temperature around at $40^{\circ}C$. The operational conditions of HPLC were as follows: Column, ODS-Hypersil ; mobile phase, 50% (v/v) acetonitrile.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.501-508
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• 2003

Artificial coupling of one enzyme with another can provide an efficient means for the production of industrially important chemicals. Xylose reductase has been recently discovered to be useful in the reductive production of xylitol. However, a limitation of its in vitro or in vivo use is the regeneration of the cofactor NAD(P)H in the enzyme activity. In the present study, an efficient process for the production of xylitol from D-xylose was established by coupling two enzymes. A NADH-dependent xylose reductase (XR) from Pichia stipitis catalyzed the reduction of xylose with a stoichiometric consumption of NADH, and the resulting cofactor $NAD^+$ was continuously re-reduced by formate dehydrogenase (FDH) for regeneration. Using simple kinetic analyses as tools for process optimization, suitable conditions for the performance and yield of the coupled reaction were established. The optimal reaction temperature and pH were determined to be about $30^{\circ}C$ and 7.0, respectively. Formate, as a substrate of FDH, affected the yield and cofactor regeneration, and was, therefore, adjusted to a concentration of 20 mM. When the total activity of FDH was about 1.8-fold higher than that of XR, the performance was better than that by any other activity ratios. As expected, there were no distinct differences in the conversion yields of reactions, when supplied with the oxidized form $NAD^+$ instead of the reduced form NADH, as a starting cofactor for regeneration. Under these conditions, a complete conversion (>99%) could be readily obtained from a small-scale batch reaction.

• Archives of Pharmacal Research
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• v.18 no.2
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• pp.75-78
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• 1995

The analysis method nad stability test of antineoplaston A10, a new anticancer drug candidate, were established. A10 and phenylacetyl- L-glutamine, one of the degradation products, can be detected by high-performance liquid chromatography. The degradation kinetics of antineoplaston A10 in aqueous solutions from pH 1 to 10 buffers were carried out at 40, 50 and 60.deg.C. Pseudo-first order kinetics were obtained throughout the entire pH ranges studied. The pH-rate profiles showed that antineoplaston A10 was very unstable in alkaline conditions and most stable at pH 4.

• YAKHAK HOEJI
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• v.19 no.1
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• pp.30-35
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• 1975

pKi values and sensitivity of acid-base indicators in the mixed solvent systems of water-alcohols and water-acetone at differential pH and in concentration media were determined by spectrophotometric method. When the concentration of the organic solvents were increased, the pKi values of sulfophthalein indicators, thymol blue and bromcresol purple, became larger whereas those of an axo indicator, methyl yellow, became smaller nad the pH values of the equivalent points of acids became smaller and the pH values of the equivalent points of acids became higher than those in the aqueous solution. potassium bicarbonate, a standard compound used in the organic solvent systems without a prerequisite procedure of expelling carbon dioxide by boiling.

• Journal of Microbiology and Biotechnology
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• v.22 no.5
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• pp.668-673
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• 2012

Biohydrogen production from organic wastewater by anaerobically activated sludge fermentation has already been extensively investigated, and it is known that hydrogen can be produced by glucose fermentation through three metabolic pathways, including the oxidative decarboxylation of pyruvic acid to acetyl-CoA, oxidation of NADH to $NAD^+$, and acetogenesis by hydrogen-producing acetogens. However, the exact or dominant pathways of hydrogen production in the anaerobically activated sludge fermentation process have not yet been identified. Thus, a continuous stirred-tank reactor (CSTR) was introduced and a specifically acclimated acidogenic fermentative microflora obtained under certain operation conditions. The hydrogen production activity and potential hydrogen-producing pathways in the acidogenic fermentative microflora were then investigated using batch cultures in Erlenmeyer flasks with a working volume of 500 ml. Based on an initial glucose concentration of 10 g/l, pH 6.0, and a biomass of 1.01 g/l of a mixed liquid volatile suspended solid (MLVSS), 247.7 ml of hydrogen was obtained after a 68 h cultivation period at $35{\pm}1^{\circ}C$. Further tests indicated that 69% of the hydrogen was produced from the oxidative decarboxylation of pyruvic acid, whereas the remaining 31% was from the oxidation of NADH to $NAD^+$. There were no hydrogen-producing acetogens or they were unable to work effectively in the anaerobically activated sludge with a hydraulic retention time (HRT) of less than 8 h.

• Microbiology and Biotechnology Letters
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• v.25 no.4
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• pp.403-407
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• 1997

Medium components for maximum activity of NAD$^{+}$-dependent formate dehydrogenase (EC 1.2.1.2; FDH) were optimized with a methanol-assimilating yeast Hansenula sp. MS-364, preserved by our laboratory. The maximum activity of the enzyme was obtained when the strain was cultivated at 30$circ$C for 24 hours in a medium containing methanol 3%(v/v), yeast extract 0.8%(w/v), K$_{2}$HPO$_{4}$, 0.1%(w/v), KH$_{2}$PO$_{4}$ 0.1%(W/V), MgSO$_{4}$, 7H$_{2}$O 0.05%(w/v), and the pH of the culture broth was adjusted at 5.0.

• Herbal Formula Science
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• v.25 no.4
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• pp.457-469
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• 2017

Obesity is one of the most serious health problem because it induced numerous metabolic syndrome and increases the incidence of various disease, including diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. In 3T3-L1 adipocytes, increases in reactive oxygens species (ROS) occur with lipid accumulation. NADPH oxidase, producing superoxide anion, may contribute to the development of obesity-associated insulin resistance and type 2 diabetes. In this study, we elucidated the effect of Chaenomeles sinensis koehne extract (CSE) against the development of obesity and the inhibition mechanisms in 3T3-L1 preadiocytes. CSE decreased triglyceride content and inhibited the expression of adipogenic transcription factors including peroxisome proliferator-activated receptor $(PPAR){\gamma}$, CCAT/enhancer binding protein $(C/EBP){\alpha}$ and sterol regulatory element-binding protein (SREBP-1). In addition, CSE highly increased antioxidant activity in a dose-dependent manner. CSE remarkably reduced intracellular ROS increase and NAD(P)H oxidase activity, NOX1, NOX4, Rac1 protein expression, and phosphorylation of p47phox and p67phox We also studied the effect of CSE on weight gain induced by high-fat diet. The oral treatment of CSE (500 mg/kg, body weight) in diet-induced obese (DIO) mice showed decrease in triglyceride and adipocyte size. Therefore, these results indicate that the effect of CSE on anti-obese effects, adipocyte differentiation and reducing triglyceride contents as well as adipocyte size in obese mice, may be associated with inhibition of NAD(P)H oxidase-induced ROS production and adipose transcription factors. These results showed the potential to inhibit the obesity by CSE treatment through controlling the activation of NAD(P)H oxidase in vitro and in vivo obese model.

• Journal of Microbiology
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• v.42 no.1
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• pp.20-24
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• 2004

Cloned myo-inositol-1-phosphate synthase (INOS) of Drosophila melanogaster was expressed in Escherichia coli, and purified using a His-affinity column. The purified INOS required NAD$\^$+/ for the conversion of glucose-6-phosphate to inositol-1-phosphate. The optimum pH for myo-inositol-1-phosphate synthase is 7.5, and the maximum activity was measured at 40$^{\circ}C$. The molecular weight of the native enzyme, as determined by gel filtration, was approximately M$\_$r/ 271,000${\pm}$15,000. A single subunit of approximately M$\_$r/ 62,000${\pm}$5,000 was detected upon SDS-polyacrylamide gel electrophoresis. The Michaelis ($K_{m}$) and dissociation constants for glucose-6-phosphate were 3.5 and 3.7 mM, whereas for the cofactor NAD$\^$+/ these were 0.42 and 0.4 mM, respectively.