• KSBB Journal
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• 제8권4호
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• pp.341-350
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• 1993

본 연구에서는 sMMO를 갖는 메탄 자화균인 M. triclwsporium OB3b를 이용하여 메탄올 생산을 위한 기초실험을 수행하였다. 중요한 결과를 요약하면 다음과 같다(Table 2). 1. 세포 내 NADH의 재생을 위해 개미산을 첨가 할 때 whole-cell의 sMMO 활성은 pH 7.0 및 $30^{\circ}C$ 에서 최대값을 보이며 propylene을 기질로 할 경우 약 130nmol/mg cell min 정도이다. 2. 인산은 MMO와 MDH 활성을 모두 저해하나 M MDH에 대한 저해 정도가 훨씬 크므로 메탄올 합성 에 사용이 가능하다. Noncompetitive mode를 가정 할 때 저해상수는 각각 185mM(MMO) 및 42mM ( (MDH)이었다. 3. 메탄올은 MMO 활성을 저해하며 noncompeti­t tive mode를 가정할 때 propylene기질의 경우 2 21mM 이었다. 4. 균체 내 sMMO 활성은 성장이 멈춰진 상태에 셔 비교적 때}른 속도로 감소하며 고농도 인산용액에 서 그 속도가 더 빨라진다. 5. 인산농도 91mM에서 메탄은 메탄올로 산화되 어 축적되며 4.5시간 동안 에탄올의 생성속도는 평 균 79nmol/mg min이었다.

• Journal of Microbiology and Biotechnology
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• 제11권5호
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• pp.825-830
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• 2001

Escherichia coli, which harbored the ars operon from a plasmid pMH12 of Klebsiella oxytoca D12, showed filamentation due to the expression of ars genes in the presence of arsenite. The continued DNA replication in the absence of cell division was revealed, since nucleoids abound with DAPI appeared to be arranged in chains. In contrast to overexpression of arsA, its frame-shift mutant and knock-out mutant lost filamentation in the presence of arsenite, which suggested that ars-induced division block was dependent on expression of arsA. ArsA-induced division inhibition was not a consequence of an inhibition of DNA replication, and the inability of arsenite to induce an SOS response indicated that arsA-mediated division inhibition was dependent on the expression of the gene product encoded by the minB operon. ArsA is a peripheral membrane protein with an ATP-binding domain, which is homologous to MinD that requires ATP-dependent efflux. These results suggested that ArsA could possibly recruit MinC to the membrane and modulate cytoplasmic FtsZ to block assembly at the middle of the cell.

• Natural Product Sciences
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• 제10권3호
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• pp.129-133
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• 2004

Quercetin is a dietary anticancer chemical that is capable of inducing apoptosis in tumor cells. However, little is known about its biological effect in nonmalignant hepatic cells. Using embryonic normal hepatic cell line (BNL CL.2) and its SV40-transformed tumorigenic cell line (BNL SV A.8), we evaluated the effects of quercetin on cell proliferation and apoptosis. As the results, our present study demonstrated that quercetin had a selective growth inhibition in normal versus tumorigenic hepatic cells such that BNL SV A.8 cells were very sensitive to the quercetin-mediated cytotoxicity. In particular, as evidenced by the increased number of positively stained cells in the TUNEL assay, the induction of characteristic nuclear DNA ladders, and the migration of many cells to sub-G1 phase in the BNL SV A.8 cells, quercetin treatment more sensitively induced apoptosis in BNL SV A8 cells than in BNL CL.2 cells. Collectively, our findings suggest that quercetin can be approached as a potential agent that is capable of inducing selective growth inhibition and apoptosis of hepatic cancer cells.

• Journal of Microbiology
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• 제40권1호
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• pp.33-37
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• 2002

An enzymatic reaction for the production of D-alanine from D-aspartic acid and pyruvate as substrates by a thermostable D-amino acid aminotransferase (D-AAT) was investigated at various conditions In the temperature range of 40-70$\^{C}$ and pH range of 6.0-9.5. The D-AAT was produced with recombinant E. coli BL21, which hosted the chimeric plasmid pTLK2 harboring the D-AAT from the novel thermophilic Bacillus sp. LK-2. The enzyme reaction was shown to follow the Ping Pong Bi Bi mechanism. The K$\_$m/ values for D-aspartic acid and pyruvate were 4.38 mar and 0.72 mM, respectively. It was observed that competitive inhibition by D-alanine, the product of this reaction, was evident with the inhibition constant K$\_$i/ value of 0.1 mM. A unique feature of this reaction scheme is that the decorboxylation of oxaloacetic acid, one of the products, spontaneously produces pyruvate. Therefore, only a catalytic amount of pyruvate is necessary for the enzyme conversion reaction to proceed. A typical time-course kinetic study skewed that D-alanine up to 88 mM could be produced from 100 mM of D-aspartic acid with a molar yield of 1.0.

• Natural Product Sciences
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• 제15권3호
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• pp.134-138
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• 2009

In an attempt to establish anti-ulcerogenic activity of potato tubers, inhibitory activity against ethanol- and indomethacin-induced gastric ulcer models in rats was evaluated for the first time. From several varieties of potato tubers including Solanum tuberosum L. cv. Superior (white skin and fresh potato) and two new varieties of (Bora valley and Gogu valley), raw potato juice was prepared and the starch was obtained from each juice by filtration and drying. Upon oral administration to rats, raw potato juice showed more or less inhibitory activity. The starch showed higher and dose-dependent inhibitory activity, suggesting that the active ingredient in raw potato juice may be the starch. Particularly, the starch obtained from the tubers of new potato variety, "Bora valley," with purple color, showed the highest inhibitory activity (62.4% and 37.1% inhibition of ulcer index at 500 mg/kg), while omeprazole (proton pump inhibitor) used as a reference drug showed 74.4% and 75.7% inhibition at 20 mg/kg against ethanol- and indomethacin-induced ulcer formation, respectively. The present study provides a first evidence of anti-ulcerogenicity of raw potato juice and the starch. Especially, the starch from "Bora valley" strongly inhibited ulcer formation in rats. Considering that these are food components, they may be safely used for anti-ulcerogenic nutraceuticals.

• BMB Reports
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• 제40권3호
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• pp.396-403
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• 2007

Proline accumulation has been shown to correlate with tolerance to drought and salt stresses in plants. We attempt to introduce the wild-type, mutant, and fusion proBA genes derived from Bacillus subtilis into Arabidopsis thaliana under the control of a strong promoter cauliflower mosaic virus 35S (CaMV35S). The transgenic plants produced higher level of free proline than control and the overproduction of proline resulted in the increased tolerance to osmotic stress in transgenic plants. Besides, the mutation in proBA genes, which were proved to lead $\alpha$-glutamyl kinase ($\alpha$-GK) reduces sensitivity to the end-product inhibition and the fusion of proB and proA also result in increasing proline production and confer osmotolerance in transgenic lines.

• Natural Product Sciences
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• 제18권4호
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• pp.261-265
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• 2012

Xanthohumol was isolated from hops (Humulus lupulus L.), and then investigated anti-oxidant effect by AAPH-induced LLC-PK1 cell and oxygen radical absorbance capacity (ORCA) assays and MMP-12 inhibitory effect by direct MMP-12 inhibition assay. The treatment of xanthohumol protected LLC-PK1 cells from AAPH-induced cell damage such as cell viability, SOD and GSH-px reduction in a dose dependant manner (0.1, 1, and $5{\mu}M$), the SOD value was 2.98, 4.51, and 5.77 U/mg protein, and GSH-px value was 30.12, 49.32, and 60.11 U/mg protein. ORAC value of xanthohumol was showed as 4320, 12004, and $14209{\mu}M$ TE/g at the concentration 0.1, 1, and $5{\mu}M$, respectively. The change of SOD and GSH-px values was significantly correlated with the results of ORAC assay, that is, AAPH-induced cell and ORCA assays. In addition, inhibition of MMP-12 that is known to play an important role in skin aging was 14%, 37%, 46%, and 79% at the concentration of 0.01, 0.1, 1, and $5{\mu}M$, respectively. On the basis of these results, xanthohumol from hops (Humulus lupulus L.) showed interesting biological and pharmacological activity such as anti-oxidant effect and anti-aging.

• 생약학회지
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• 제42권1호
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• pp.61-67
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• 2011

In this study, we evaluated the bioactivities of methanol extract and its solvent fractions of Sonchus asper (L.) Hill. The EtOAc fraction of S. asper exhibited more strong antioxidant activity than other extracts as evidenced by the strongest 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity with a $EC_{50}$ value at $33.55\;{\mu}g/mL$ and reducing power, the total polyphenol (180.71 mg GAE/g) and flavonoid contents (145.86 mg QE/g) of S. asper extract were higher than other extracts. The EtOAc fraction of the S. asper also showed 47.38% mushroom tyrosinase inhibition activity, 56.22% ${\alpha}$-glucosidase inhibition and 46.58% ${\alpha}$-amylase inhibition ratio at 1 mg/mL. Both methylene chloride and EtOAc fractions of methanol extract of S. asper effectively reduced of the 86.34% and 62.03% angiotensin I converting enzyme (ACE) activity at 2 mg/mL, respectively. These findings suggest that the EtOAc fraction of the S. asper could be a potential antioxidant in food additive, medicinal, and industry product.

• Natural Product Sciences
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• 제23권1호
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• pp.5-8
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• 2017

An antimicrobial compound has been isolated from the leaves of Glochidion superbum. The compound was determined as methyl 3, 4, 5-trihydroxybenzoate (methyl gallate), based on ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS) analysis. The isolated compound exhibited potent antimicrobial activity against three clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) by qualitative agar disc diffusion method and quantitative broth dilution method. Agar disc diffusion was done in a dose-dependent manner for each bacterial isolate at disc potencies of 25, 50, 100, and $150{\mu}g/disc$. The zones of inhibition were on average equal to 12.27, 14.20, 15.43, and 24.17 mm respectively. The inhibition zones were compared with that of vancomycin disc at $30{\mu}g$ as a reference standard. The MIC and MBC values were $50{\mu}g/ml$ and $100{\mu}g/ml$ respectively. The results of anti MRSA activity were analyzed using one-way ANOVA with Turkey's HSD and Duncan test. In conclusion, methyl gallate which was isolated from G. superbum showed the inhibition activity against methicillin resistant S. aureus.

• Corrosion Science and Technology
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• 제3권6호
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• pp.227-232
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• 2004

The carboxylates as a corrosion inhibitor has been studied by many researchers because of its environmental safety and low depletion rate. However, conventional test methods of inhibitor such as weight loss measurements, linear polarization resistance and corrosion potential monitoring etc., evaluate uniform corrosion of metals. These methods are unable to evaluate crevice-related corrosions, which are encountered in most of heat exchanging facilities. In order to choose the optimum corrosion inhibitor, the appropriate test methods are required to evaluate their performances in service environment. From this point of view, polarization technique was used to evaluate the characteristics of sodium heptanoate on corrosion behavior for carbon steel. Especially a thin film crevice sensor technique were applied to simulate the crevice corrosion in this study. From these experiments, we found that oxygen as an oxidizing agent was required to obtain stable passive film on the metal. Presence of oxygen, however, accelerated crevice corrosion. Potential shift by oxygen depletion and weakened inhibitive film inside the crevice were responsible for such accelerated feature. It is shown that film for corrosion inhibition is a mixture of sodium heptanoate and iron (II) heptanoate as reaction product of iron surface and sodium heptanoate. The iron (II) heptanoate which has been synthesized by reaction of heptanoic acid and ferrous chloride in methanol solution forms bidentate complex.