• YAKHAK HOEJI
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• v.21 no.3
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• pp.167-171
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• 1977

A new assay method for delta-l-dehydrogenated-3-ketoco-rticosteroid in the presence of proteinous material or whole-cell-enzyme and 3-ketocorticosteroid has been developed. This method makes use of the linear relationship between the ratio of absorbances at 265 nm and at 242 nm and the fractional concentration of delta-1-3-ketosteroid. Theoretical values were calculated based on the absorbances of proteinous material at fixed concentrations of the 3-ketosteroid and delta-1-dehydrogenated-3-ketosteroid. The values obtained experimentally showed good agreement with the values obtained experimentally showed good agreement with the values theoretically predicted. The new assay method developed for the steroid mixtiure containing proteinous material is of some practical importance. The use of such assay method enables one to determine the enzyme activity and the rate of enzyme reaction or conversion rather quickly, easily and accurately. By the use of this assay method, the reaction kinetics of whole-cell-enzyme has also been studied. It was found that it followed the simple Michaelis-Menten type enzyme kinetics. Also the reversibility of this reaction with actively metabolizing cell was examined. It was found that delta-l-dehydrogenated-3-ketosteroid could not be hydrogenated reversibly to 3-ketosteroid by this enzyme system.

• Food Engineering Progress
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• v.15 no.4
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• pp.289-296
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• 2011

Twenty four fractions by solvent extraction and/or acid precipitation from fruit body and culture broth of Inonotus obliquus were prepared, and their inhibitory effect against acetylcholinesterase (AChE) was investigated. Among these fractions, acid (1 M HCl) precipitates from cell-free culture broth and fruit body exhibited the highest inhibitory effect on AChE in vitro. Acid precipitates inhibited AChE activity in a concentration-dependant manner and $IC_{50}$ values of both acid precipitates were 0.53 mg/mL. The inhibition pattern was general non-competitive inhibition. The energetic parameters were also determined by dual substrate/temperature design. Both acid precipitates increased the values of Ea, ${\Delta}H,/;{\Delta}G$ and ${\Delta}H^{\ast}$ decreasing the value of ${\Delta}S$ for AChE. The results implied that the acid precipitates from I. obliquus increased the thermodynamic barrier, leading to the breakdown of ES complex and the formation of products as inhibitory mechanism.

• Journal of Microbiology and Biotechnology
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• v.23 no.8
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• pp.1099-1106
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• 2013

Tuta absoluta (Povolny, 1994) is a devastating moth to the Solanaceae plants. It is a challenging pest to control, especially on tomatoes. In this work, we studied the entomopathogenic activity of the Cry-forming ${\delta}$-endotoxins produced by Bacillus thuringiensis strain KS and B. thuringiensis kurstaki reference strain HD1 against T. absoluta. These strains carried the cry2, cry1Ab, cry1Aa/cry1Ac, and cry1I genes, and KS also carried a cry1C gene. The ${\delta}$-endotoxins of KS were approximately twofold more toxic against the third instar larvae than those of HD1, as they showed lower 50% and 90% lethal concentrations (0.80 and 2.70 ${\mu}g/cm^2$ (${\delta}$-endotoxins/tomato leaf)) compared with those of HD1 (1.70 and 4.50 ${\mu}g/cm^2$) (p < 0.05). Additionally, the larvae protease extract showed at least six caseinolytic activities, which activated the KS and HD1 ${\delta}$-endotoxins, yielding the active toxins of about 65 kDa and the protease-resistant core of about 58 kDa. Moreover, the histopathological effects of KS and HD1 ${\delta}$-endotoxins on the larvae midgut consisted of an apical columnar cell vacuolization, microvillus damage, and epithelial cell disruption. These results showed that the KS strain could be a candidate for T. absoluta control.

• Bulletin of the Korean Chemical Society
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• v.18 no.6
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• pp.618-622
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• 1997

The polysiloxane-bridged dinuclear metallocenes $[(SiMe_2O)_n-SiMe_2(C_5H_4)_2][(C_9H_7)ZrCl_2]_2$ (n=1 (7), 2 (8), 3 (9)) have been generated as a model complex for the immobilized metallocene at silica surface by treating the respective disodium salts of the ligands with 2 equivalents of $(C_9H_7)ZrCl_3$ in THF. All three complexes are characterized by $^1H$ NMR and measurement of metal content through ICP-MS. It turned out that the values of ${\Delta}{\delta}=[{\delta}_d-{\delta}_p]$, the chemical shift difference between the distal $({\delta}_d)$ and proximal $({\delta}_p)$ protons, for the produced dinuclear compounds (0.47 for 7, 0.49 for 8, and 0.5 for 9) were larger than the Δδ value of the known ansa-type complex holding the same ligand as a chelating one, that is just the opposite to the normal trend. In order to compare polymerization behavior of the dinuclear metallocene with the corresponding mononuclear metallocene, (Cp)$(C_9H_7)ZrCl_2$ was separately prepared. To investigate the catalytic properties of the dinuclear complexes and mononuclear metallocenes ethylene polymerization has been conducted in the presence of MMAO. The polymerization results display the typical activity dependence on polymerization temperature for all complexes. The most important feature is that the polymers from the dinuclear metallocenes represent enormously improved molecular weight compared with the polymer from the corresponding mononuclear metallocene. In addition, the influence of the nature of the bridging ligand upon the reactivities of the dinuclear metallocenes has also been observed.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.957-961
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• 2005

Spoilage yeast was isolated from spoiled rice-syrup and identified by Microbial Identification system (MIDI) as Zygosaccharomyces bailii based on composition of fatty acids exhibiting carbon skeleton of 16:0, 16.1 $({\Delta}cis\;7)$, 18:2 $({\Delta}cis\;9)$, 18:1 $({\Delta}cis\;9)$, and 18:1. Increase in sugar content $(1^{\circ}brix)$ resulted in decreased moisture concentration (1%), and water activity decreased from 0.72 to 0,63 when sugar concentration increased from 77 to $83^{\circ}brix$. Yeast showed very slow growth during three weeks post-inoculation in rice-syrup at 17 and $79^{\circ}brix$, and maximal level of Z. bailii was found at 6 and 10 weeks storage at 15 and $25^{\circ}C$, respectively. At over $81^{\circ}brix$ its growth slowly decreased at beginning of storage, indicating rice-syrup could be preserved safely at above $81^{\circ}brix$ sugar content without Z. bailii contamination.

• BMB Reports
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• v.34 no.5
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• pp.402-407
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• 2001

Based on the currently proposed toxicity model for the different Bacillus thuringiensis Cry $\delta$-endotoxins, their pore-forming activity involves the insertion of the ${\alpha}4-{\alpha}5$ helical hairpin into the membrane of the target midgut epithelial cell. In this study, a number of polar or charged residues in helix 4 within domain I of the 65-kDa dipteranactive Cry11A toxin, Lys-123, Tyr-125, Asn-128, Ser-130, Gln-135, Arg-136, Gln-139 and Glu-141, were initially substituted with alanine by using PCR-based directed mutagenesis. All mutant toxins were expressed as cytoplasmic inclusions in Escherichia coli upon induction with IPTG. Similar to the wild-type protoxin inclusion, the solubility of each mutant inclusion in the carbonate buffer, pH 9.0, was relatively low When E. coli cells, expressing each of the mutant proteins, were tested for toxicity against Aedes aegypti mosquito-larvae, toxicity was completely abolished for the alanine substitution of arginine at position 136. However, mutations at the other positions still retained a high level of larvicidal activity Interestingly, further analysis of this critical arginine residue by specific mutagenesis showed that conversions of arginine-136 to aspartate, glutamine, or even to the most conserved residue lysine, also abolished the wild-type activity The results of this study revealed an important determinant in toxin function for the positively charged side chain of arginine-136 in helix 4 of the Cry11A toxin.

• Mycobiology
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• v.40 no.3
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• pp.173-180
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• 2012

A ${\beta}$-glucosidase from Penicillium italicum was purified with a specific activity of 61.8 U/mg, using a chromatography system. The native form of the enzyme was an 88.5-kDa tetramer with a molecular mass of 354 kDa. Optimum activity was observed at pH 4.5 and $60^{\circ}C$, and the half-lives were 1,737, 330, 34, and 1 hr at 50, 55, 60, and $65^{\circ}C$, respectively. Its activity was inhibited by 47% by 5 mM $Ni^{2+}$. The enzyme exhibited hydrolytic activity for p-nitrophenyl-${\beta}$-D-glucopyranoside (pNP-Glu), p-nitrophenyl-${\beta}$-D-cellobioside, p-nitrophenyl-${\beta}$-D-xyloside, and cellobiose, however, no activity was observed for p-nitrophenyl-${\beta}$-D-lactopyranoside, p-nitrophenyl-${\beta}$-D-galactopyranoside, carboxymetyl cellulose, xylan, and cellulose, indicating that the enzyme was a ${\beta}$-glucosidase. The $k_{cat}/K_m\;(s^{-1}mM^{-1})$ values for pNP-Glu and cellobiose were 15,770.4 mM and 6,361.4 mM, respectively. These values were the highest reported for ${\beta}$-glucosidases. Non-competitive inhibition of the enzyme by both glucose ($K_i=8.9mM$) and glucono-${\delta}$-lactone ($K_i=11.3mM$) was observed when pNP-Glu was used as the substrate. This is the first report of non-competitive inhibition of ${\beta}$-glucosidase by glucose and glucono-${\delta}$-lactone.

• Journal of Life Science
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• v.17 no.5 s.85
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• pp.658-663
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• 2007

Bacillus thuringiensis is a well-known species of entomophathogenic bacteria that is widely used as a biopesticide against many insect pests. It produces parasporal crystals ($\delta$-endotoxin) and endospores during sporulation. In this report, the $\delta$-endotoxin produced by Bacillus thuringiensis BT-1 and BT-2 were characterized by Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM), SDS-PACE, and solubilization activity by alkaline solution. BT-1, BT-2 were cultured in the GBY medium, and the $\delta$-endotoxin of them was purified with discontinuous sucrose density gradient centrifugation. Their $\delta$-endotoxin was observed by SEM and TEM. Morphologically, the $\delta$-endotoxin of BT-1 was a square and flat type, whose size was $1.73{\mu}m{\times}0.7{\mu}m$, and the $\delta$-endotoxin of the BT-2 was spherical form whose size was $1.1{\mu}m{\times}0.9{\mu}m$ determined by SEM and TEM. The $\delta$-endotoxin of the BT-1 was composed of 28 kDa and 21 kDa, however, it of the BT-2 was composed of 50 kDa, 35 kDa, and 22 kDa bands determined by SDS-PACE. The purified crystals of BT-1 and BT-2 were dissolved gradually in alkaline solution as time goes by, and it was perfectly dissolved after 3 hours. It is supposed that the $\delta$-endotoxin of crystal was converted to a state of activation in the course of time in the intestines of insect.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3709-3714
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• 2013

Based on the Debye-H$\ddot{u}$ckel equation, a semi-empirical equation for activity coefficients was derived through empirical and theoretical trial and error efforts. The obtained equation included two parameters: the proportional factor and the effective radius of an ionic sphere. These parameters were used in the empirical and regression parameter fitting of the calculated values to the experimental results. The activity coefficients calculated from the equation agreed with the data. Transforming to a semi-empirical form, the equation was expressed with one parameter, the ion radius. The ion radius, ${\alpha}$, was divided into three parameters, ${\alpha}_{cation}$, ${\alpha}_{anion}$ and ${\delta}_{cation}$, representing parameters for the cation, anion and combination, respectively. The advantage of this equation is the ability to propose a semi-empirical equation that can easily determine the activity coefficient with just one parameter, so the equation is expected to be used more widely in actual industry applications.

• BMB Reports
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• v.36 no.6
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• pp.608-610
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• 2003

Escherichia coli has two catalases, HPI and HPII. HPI is induced during logarithmic growth in response to low concentrations of hydrogen peroxide. This induction is OxyR-dependent. On the other hand, HPII is not peroxide-inducible but is induced in entry to the stationary phase. We demonstrate here that E. coli displayed higher HPI catalase activity when compared to the cultures that were grown in a normal medium, if grown in a medium supplemented with iron-citrate. Iron supplementation had no effect on HPII catalase. This increase of HPI activity was OxyR-independent and not observed in a ${\Delta}fur$ mutant. The physiological significance of the increase of HPI activity is unclear, but it appears that the katG gene that codes for HPI catalase is among the genes that are regulated by Fur.