• BMB Reports
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• 제40권1호
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• pp.100-106
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• 2007

The wound-inducible lipoxygenase obtained from maize is one of the nontraditional lipoxygenases that possess dual positional specificity. In this paper, we provide our results on the determination and comparison of the kinetic constants of the maize lipoxygenase, with or without detergents in the steady state, and characterization of the dependence of the kinetic lag phase or initial burst, on pH, substrate, and detergent in the pre-steady state of the lipoxygenase reaction. The oxidation of linoleic acid showed a typical lag phase in the pre-steady state of the lipoxygenase reaction at pH 7.5 in the presence of 0.25% Tween-20 detergent. The reciprocal correlation between the induction period and the enzyme level indicated that this lag phenomenon was attributable to the slow oxidative activation of Fe (II) to Fe (III) at the active site of the enzyme as observed in other lipoxygenase reactions. Contrary to the lagging phenomenon observed at pH 7.5 in the presence of Tween-20, a unique initial burst was observed at pH 6.2 in the absence of detergents. To our knowledge, the initial burst in the oxidation of linoleic acid at pH 6.2 is the first observation in the lipoxygenase reaction. Kinetic constants (Km and kcat values) were largely dependent on the presence of detergent. An inverse correlation of the initial burst period with enzyme levels and interpretations on kinetic constants suggested that the observed initial burst in the oxidation of linoleic acid could be due to the availability of free fatty acids as substrates for binding with the lipoxygenase enzyme.

• 농업생명과학연구
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• 제45권6호
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• pp.201-212
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• 2011

인천 연안의 심하게 오염된 갯벌로부터 강력한 세포외 알카리성 단백질 분해효소를 생산하는 호알카리성 Bacillus clausii I-52를 분리하였으며, 이 균주로부터 알카리성 단백질 분해효소의 유전자를 cloning하여 서열 분석을 하였다. Chromosome 서열이 완전히 밝혀진 Bacillus subtilis의 서열을 기초로 하여 알카리성 단백질 분해효소 및 promoter를 포함하도록 primer를 고안하여 PCR을 수행하여 2,277 bp의 DNA 단편을 얻었으며 BLAST 분석 결과 29 개의 아미노산으로 이루어진 signal peptide, 77 개의 아미노산으로 이루어진 propeptide 및 275 개의 아미노산을 갖는 활성형의 BCAP으로 구성된 총 381 개의 아미노산을 코딩하는 1,143 bp의 open reading frame을 확인하였다. 활성형 BCAP의 N-말단 아미노산은 Ala이며, 분자량 및 pI 값은 각각 27698.7 Da과 6.30으로 계산되었다. 아미노산 상동성을 분석한 결과, B. subtilis 유래의 nattokinase precursor 및 B. subtilis BSn5 유래의 subtilisin E precursor와 99%의 서열 상동성을 나타내어 B. clausii I-52 유래의 BCAP은 subtilisin 계열의 단백질 분해효소임을 확인하였다. E. coli BL21(DE3)에서 발현한 재조합 BCAP는 N-Suc-Ala-Ala-Pro-Phe-pNA 를 효율적으로 분해하였다. Refolding한 재조합 BCAP은 전형적인 serine protease inhibitor인 PMSF에 의하여 강하게 효소 활성이 억제됨으로써 serine protease 계열의 단백질 분해효소임을 알 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제27권4호
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• pp.775-784
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• 2017

A neutral xylanase (CcXyn) was identified from Coprinus cinereus. It has a single GH10 catalytic domain with a basic amino acid-rich extension (PVRRK) at the C-terminus. In this study, the wild-type (CcXyn) and C-terminus-truncated xylanase ($CcXyn-{\Delta}5C$) were heterologously expressed in Pichia pastoris and their characteristics were comparatively analyzed with aims to examine the effect of this extension on the enzyme function. The circular dichorism analysis indicated that both enzymes in general had a similar structure, but $CcXyn-{\Delta}5C$ contained less ${\alpha}-helices$ (42.9%) and more random coil contents (35.5%) than CcXyn (47.0% and 32.8%, respectively). Both enzymes had the same pH (7.0) and temperature ($45^{\circ}C$) optima, and similar substrate specificity on different xylans. They all hydrolyzed beechwood xylan primarily to xylobiose and xylotriose. The amounts of xylobiose and xylotriose accounted for 91.5% and 92.2% (w/w) of total xylooligosaccharides (XOS) generated from beechwood by CcXyn and $CcXyn-{\Delta}5C$, respectively. However, truncation of the C-terminal 5-amino-acids extension significantly improved the thermostability, SDS resistance, and pH stability at pH 6.0-9.0. Furthermore, $CcXyn-{\Delta}5C$ exhibited a much lower $K_m$ value than CcXyn (0.27 mg/ml vs 0.83 mg/ml), and therefore, the catalytic efficiency of $CcXyn-{\Delta}5C$ was 2.4-times higher than that of CcXyn. These properties make $CcXyn-{\Delta}5C$ a good model for the structure-function study of $({\alpha}/{\beta})_8$-barrel-folded enzymes and a promising candidate for various applications, especially in the detergent industry and XOS production.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.88-92
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• 2005

Aptamer is the single-stranded oligonucleotide which binds to various target molecules such as proteins, peptides, lipids and small organic molecules with high affinity and specificity. DNA aptamers specific for the $17{\beta}-estradiol$ were selected by SELEX (Systematic Evolution of Ligands by EXponential enrichment) process from a random DNA library. These DNA aptamers have a high affinity to $17{\beta}-estradiol$ as an endocrine disrupting chemical. Nanowell and $200{\mu}m$ gold electrode were used as substrate for DNA aptamer immobilization and electrochemical analysis. Especially, nanowell gold electrode was fabricated by e-beam lithography. The size of single nanowell is 130nm and 40,000 nanowells were deposited on one gold electrode. The immobilization method was based on the interaction between the biotinylated aptamer and streptavidin deposited on gold electrode previously. Immobilization procedure was optimized by surface plasma resonance (SPR) and electrochemical analysis. After the immobilization of DNA aptamer on streptavidin modified gold electrode, $17{\beta}-estradiol$ solution was treated on aptamer immobilized gold electrode. The current of gold electrode was decreased by the binding of $17{\beta}-estradiol$ to DNA aptamer immobilized on gold electrode. However, in negative control experiments of 1-aminoanthraquinone and 2-methoxynaphthalene, the current was rarely decreased. And more sensitive data was obtained from nanowell gold electrode comparing with $200{\mu}m$ gold electrode.

• 한국식품과학회지
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• 제23권4호
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• pp.414-419
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• 1991

돼지감자의 가공과정 중 갈변에 관여하는 polyphenol oxidase를 부분 정제하고 이의 특성을 조사하였다. 인산완충액으로 추출된 조효소가 ammonium sulfate에 의한 침전과 Sephadex G-100에 의한 gel filtration으로 48배 정제되었다 이 효소는 catechol을 기실로 하였을 때 최적 활성 pH가 6.5이었으며 $K_{m}$값은 3mM, 열불활성 화는 1차반응을 보였고, 이때 Z값은 $7.6^{\circ}C$, 활성화에너지($E_{a}$)는 72.6kcal/mole이었다. 이 효소를 인산완충액에 저장하였을 때 $4^{\circ}C$에서는 일주일 이상 안정하였으나 $25^{\circ}C$에서는 활성이 급격히 소실되었다. 이 효소는 monophenol에는 반응하지 않고 diphenol의 기질에만 친화력을 나타내었으며, 그 중 chlorogenic acid와 가장 잘 반응하였다. 그리고 1 mM의 L-cystein(HCl)와 L-hydrosulfite, L-ascorbic acid에 의해서 완전히 저해되었다.

• BMB Reports
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• 제31권3호
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• pp.221-226
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• 1998

Phosphorylation of phytochrome may play important functional roles to control plant photomorphogenesis. Many attempts have failed to identify the protein kinase that phosphorylates phytochrome in vivo. It has been reported that a polycation-stimulated protein kinase activity was associated with the purified phytochrome. However, it is not known if the kinase activity is an intrinsic property of phytochrome or whether it comes from a contaminant of the purified phytochrome. In the present study, three protein kinases that phosphorylate phytochrome have been identified from etiolated oat seedlings. A polycationstimulated protein kinase that had very similar enzymatic properties with that associated with the purified phytochrome was identified in the cytosolic extract. It phosphorylated several contaminant proteins in the kinase preparation as well as phytochrome and had a broad substrate specificity. A CK II-type protein kinase phosphorylated phytochrome and the exogenously added casein. It is likely that this kinase may not be a feasible candidate for the kinase phosphorylating phytochrome in vivo since the content of the kinase seemed to well exceed the content of phytochrome in the etiolated oat seedlings. Another protein kinase that had unique enzymatic properties phosphorylated phytochrome very specifically and seemed to be present in a small quantity in the etiohlted seedlings. It is expected that one of three kinases may be responsible for the phytochrome phosphorylation in vivo.

• BMB Reports
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• 제31권3호
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• pp.274-280
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• 1998

An inositol monophosphatase (IMPase) was purified to homogeneity from rat duodenal mucosa for the first time and its enzymatic properties were investigated. Rat duodenal mucosa peculiarly exhibited the highest IMPase activity among various rat tissues examined. By means of ammonium sulfate precipitation, followed by Q-Sepharose, polylysine agarose, reactive-red agarose column chromatography, Uno-Q FPLC, and Bio-Silect FPLC, duodenal IMPase was purified 223-fold to a specific activity of 13.6 U/mg protein. The molecular mass of the native enzyme was estimated to be 48,000 Da on gel filtration. The subunit molecular mass was determined by SDS-PAGE to be 24,000 Da. These results indicate that duodenal IMPase is a dime ric protein made up of identical subunits. Rat duodenal IMPase has distinct properties from brain IMPase. It has a broad spectrum of substrate specificity and is insensitive to $Li^+$. Duodenal IMPase does not absolutely require $Mg^{2+}$ for its catalytic activity. Furthermore, duodenal IMPase is less stable to heat than brain enzyme. It is suggested that the rat duodenal mucosa needs a large amount of IMPase whose properties are quite different from that of the brain enzyme.

• Journal of Plant Biotechnology
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• 제2권2호
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• pp.79-82
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• 2000

We have isolated a cDNA encoding a calcium-dependent protein kinase (CDPK) in Nicotiana tabacum, which was designated NtCDPK1. Accumulation of the NtCDPK1 mRNA was stimulated by various stimuli, including phytohormones, CaCl$_2$ wounding, fungal elicitors, chitin and methyl jasmonate. The NtCDPK1 gene encodes a functional Ser/Thr protein kinase of which phosphorylation activity is strongly induced by calcium. By analyzing expression of the NtCDPK1-GFP fusion protein and by immunoblotting with antibody which reacts with NtCDPK1, we found that NtCDPK1 is localized in membrane and nucleus in plant cells. Silencing expression of the NtCDPK1 transgene resulted in marked decrease of lateral root development in the transgenic tobacco plants. Yeast two hybrid screening using NtCDPK1 as a bait identified a tobacco homologue of proteasome regulatory subunit 21D7, designated Nt21D7. The 21D7 mRNA has been shown to be predominantly expressed in proliferating tissues in the cell cycledependent manner in carrot. The recombinant NtCDPK1 protein associated with Nt21D7 in vitro, and could phosphorylate the Nt21D7 protein in vitro in the presence of calcium, suggesting that Nt21D7 protein is a natural substrate of NtCDPK1 in tobacco. These results suggest that NtCDPK1 may regulate tell proliferation processes, such as lateral root formation, by regulating specificity and/or activity of proteasome-mediated protein degradation pathway.

• 한국균학회지
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• 제32권2호
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• pp.119-124
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• 2004

쓴송이버섯으로부터 분리한 혈전용해효소(TSFE)의 활성은 11.42 U/mg이었으며, N-terminal amino acid 서열은 Ala-Thr-Tyr-Lys-Ile-X-Ser-Ala-Thr-His-Gln-X-X-Leu-Val로 지금까지 발표되지 않은 새로운 효소였다. MALDI-TOF와 ICP/MS로 분자량은 18788.25 Da이며, $Zn^{2+}$을 함유하는 금속효소임을 알게 되었다. 이 효소는 $40^{\circ}C$까지 열에 안정하고, 특히 합성된 기질 Lys pNA를 강하게 분해하였다. $Zn^{2+}$와 $Co^{2+}$에 의해 활성이 증가되고, EDTA, 1,10-phenanthroline, $Hg^{2+}$에 의해서는 활성이 완전히 소멸되었다. 이 효소는 섬유소원의 $A{\alpha}$ chain은 분해하지만, $B{\beta}$ chain과 ${\gamma}$ chain은 분해하지 못했다.

• Journal of Dairy Science and Biotechnology
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• 제29권1호
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• pp.49-54
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• 2011

담즙산 분해효소(Bile salt hydrolase, EC 3.5.1.24) 활성은 담즙산의 카르복실기와 결합되어 있는 아미노기(glycine or taurine)와의 amide 결합을 끊는 작용을 하며, 이 효소 활성은 사람이나 동물의 장내 미생물들에서 널리 분포하고 있다. 노인 분변으로부터 분리한 여러 균주의 Enterococcus faecalis중에서 BSH activity가 가장 높은 CU30-2를 선발하였다. BSH 유전자를 pET22b expression vector에 클로닝하여 Escherichia coli BL21(DE3) Gold를 이용하여 단백질을 발현하였다. 6x His-tag이 있는 BSH 효소를 $Ni^+$-NTA agarose column을 이용하여 분리 정제하였고, 6가지의 다른 담즙산염을 이용하여 기질 특이성을 비교하였다. E. faecalis CU30-2의 BSH 효소는 glycine이 결합된 담즙산염에 대한 효소활성이 taurine이 결합된 것에 대한 활성보다 약 50배 정도 높게 나타났다. 이 효소의 최적 pH와 온도는 각각 7.0과 40$^{\circ}C$로 확인되었다.