• Carbon letters
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• 제24권
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• pp.103-110
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• 2017

Carbon-based magnetic nanostructures in several instances have resulted in improved physicochemical and catalytic properties when compared to multi-wall carbon nanotubes (MWCNTs) and magnetic nanoparticles. In this study, magnetic MWCNTs with a structure of $Ni_xZn_xFe_2O_4/MWCNT$ as peroxidase mimics were fabricated by the one-pot hydrothermal method. The structure, composition and morphology of the nanocomposites were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy and transmission electron microscopy. The magnetic properties were investigated with a vibrating sample magnetometer. The peroxidase-like catalytic activity of the nanocomposites was investigated by colorimetric and electrochemical tests with 3,3',5,5'-tetramethylbenzidine (TMB) and $H_2O_2$ as the substrates. The results show that the synthesis of the nanocomposites was successfully performed. XRD analysis confirmed the crystalline structures of the $Ni_xZn_xFe_2O_4/MWCNT$ nanohybrids and MWCNTs. The main peaks of the $Ni_xZn_xFe_2O_4/MWCNT$s crystals were presented. The $Ni_{0.25}Zn_{0.25}Fe_2O_4/MWCNT$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4/MWCNT$ nanocatalysts showed nearly similar physicochemical properties, but the $Ni_{0.5}Zn_{0.5}Fe_2O_4/MWCNT$ nanocatalyst was more appropriate than the $Ni_{0.25}Zn_{0.25}Fe_2O_4/MWCNT$ nanocatalyst in terms of the magnetic properties and catalytic activity. The optimum peroxidase-like activity of the nanocatalysts was obtained at pH 3.0. The $Ni_{0.5}Zn_{0.5}Fe_2O_4/MWCNT$ nanocatalyst exhibited a good peroxidase-like activity. These magnetic nanocatalysts can be suitable candidates for future enzyme-based applications such as the detection of glucose and $H_2O_2$.

• Journal of Microbiology and Biotechnology
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• 제16권7호
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• pp.1041-1046
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• 2006

Selenium-containing peptide (selenium peptide) was produced by autolysis of total proteins of Saccharomyces cerevisiae grown with inorganic selenium. Selenium peptide exhibited antioxidant activity as a glutathione peroxidase (GPx) mimic, and its activity was dependent on the hydrolysis methods. The GPx-like activity of the hydrolyzed selenium peptide increased 2.7-folds when digested by protease, but decreased by acid hydrolysis. During the autolysis of the yeast cell, the GPx-like activity and selenium content increased 4.3- and 2.3-folds, respectively, whereas the average molecular weight (MW) of selenium peptide decreased 70%. The GPx-like activity was dependent on the MW of selenium peptide and was the highest (220 U/mg protein) at 9,500 dalton. The maximum GPx-like activity (28,600 U/g cell) was obtained by 48 h of autolysis of the cells, which were precultured with 20 ppm of selenate. Selenium peptide showed little toxicity, compared with highly toxic inorganic selenium. These results show the potential of selenium peptide as a nontoxic antioxidant that can be produced by simple autolysis of yeast cells.

• Applied Microscopy
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• 제28권3호
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• pp.399-414
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• 1998

Glandular trichomes present on the leaf surface of Drosera capensis were examined using transmission electron microscopy. A large number of stalked glands exist on the adaxial surfaces of the leaf blade. The secretory head is composed of two layers of secretory cells, one layer of middle cells, and the inner tracheids. The secretory cells contain rough endoplasmic reticulum, mitochondria, plastids, Golgi apparatus, and vacuoles. The secretory cells show prominent cell wall ingrowth, and thick cuticle restricted on the subcuticular wall. Frequently, the cuticle has some pores, canal-like structures, showing electron -dense granules being penetrated through them. Ultrastructural localization using diaminobenzidine showed the electron-dense deposits in the vacuole. No peroxidase activity was seen in the cell wall and cytolasm. The activity of peroxidase (POX) isozymes in Drosera which isoelectric point (pI) is 3.6 and some anionic POX isozymes which pIs are laid between 3.6 and 4.6 were especially increased according to the development and the formation of glandular trichomes. Also, the activity of some POX isozymes which isoelectric points are laid between 4.6 and 5.1 were increased in the regions of leaves which has trichomes.

• Journal of Microbiology and Biotechnology
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• 제20권3호
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• pp.532-541
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• 2010

Peroxidase-like activity of Vitreoscilla hemoglobin (VHb) has been recently disclosed. To maximize such activity, two catalytically conserved residues (histidine and arginine) found in the distal pocket of peroxidases have successfully been introduced into that of the VHb. A 15-fold increase in catalytic constant ($k_{cat}$) was obtained in P54R variant,which was presumably attributable to the lower rigidity and higher hydrophilicity of the distal cavity arising from substitution of proline to arginine. None of the modifications altered the affinity towards either $H_2O_2$ or ABTS substrate. Spectroscopic studies revealed that VHb variants harboring the T29H mutation apparently demonstrated a spectral shift in both ferric and ferrous forms (406-408 to 411 nm, and 432 to 424-425 nm, respectively). All VHb proteins in the ferrous state had a $\lambda_{soret}$ peak at ~419 nm following the carbon monoxide (CO) binding. Expression of the P54R mutant mediated the downregulation of iron superoxide dismutase (FeSOD) as identified by two-dimensional gel electrophoresis (2-DE) and peptide mass fingerprinting (PMF). According to the high peroxidase activity of P54R, it could effectively eliminate autoxidation-derived $H_2O_2$, which is a cause of heme degradation and iron release. This decreased the iron availability and consequently reduced the formation of the $Fe^{2+}$-ferric uptake regulator protein ($Fe^{2+}$-Fur), an inducer of FeSOD expression.

• 생명과학회지
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• 제33권1호
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• pp.8-14
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• 2023

Peroxidasin (PXDN)은 촉매 도메인 외에도 세포외기질 모티프를 포함한 다양한 도메인을 가진 heme peroxidase로서, collagen IV (Col IV)에서 sulfilimine 가교를 형성하여 Col IV의 스캐폴드를 강화한다. 우리는 이전 논문에서 PXDN이 sulfilimine 가교 의존적인 기질 assembly를 통하여 내피세포 생존 및 성장 신호전달에 필요하다고 보고하였다. 이 연구에서는 내피세포에서의 PXDN 기능에 있어 peroxidase 활성의 필요성을 조사하였다. 첫번째로 peroxidase 도메인의 활성 부위에 존재하며 고도로 보존된 Q823과 D826을 각각 W823, E826으로 치환한 돌연변이체를 제작하였다. 이러한 돌연변이 단백질을 높게 발현하는 HEK293 클론을 분리하였고, 이들 세포를 무혈청 배지에서 24시간 배양하여 조건 배지를 확보하여 평가하였다. 조건 배지에 대해 비환원 조건으로 Western blot 분석을 실시하였을 때, 돌연변이 단백질은 삼량체를 형성하는 것으로 관찰되었고, proprotein convertase에 의해 야생형 PXDN처럼 절단되는 것을 확인하였다. 그러나, peroxidase 활성은 돌연변이 PXDN이 포함된 조건 배지에서 야생형 PXDN과는 대조적으로 관찰되지 않았다. 또한, sulfilimine 가교 형성 능력도 돌연변이 PXDN에서 소실되었음이 확인되었다. 이에 더하여, PXDN이 depletion된 내피세포에 돌연변이 PXDN이 포함된 조건배지를 가하였을 때, 야생형 PXDN 조건배지와 달리 증식을 촉진시키지 못함을 관찰하였다. 이러한 결과들은 PXDN의 peroxidase 활성이 sulfilimine 가교를 형성하여 내피세포 성장에 영향을 미침을 제안한다.

• 대한화장품학회지
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• 제30권1호
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• pp.73-77
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• 2004

셀레늄을 함유하는 펩타이드(셀레늄 펩타이드)는 셀레늄을 함유하는 배지에서 효모를 배양함으로써 생산 하였다. 효모 단백질의 GPC 분석을 통해서 다양한 크기의 단백질 내 셀레늄 분포를 조사한 결과 셀레늄이 효모 내 단백질에 균일하게 분포하는 것을 확인하였다. 단백질당 셀레늄 양은 배지에 첨가한 셀레늄 양이 증가함에 따라 증가하였고 펩타이드 내의 셀레늄 함량이 높아질수측 항산화 효과 (glutathione peroxidase 유사 활성)가 증가하였다. 단백질 가수분해효소 XIV를 이용하여 여러 분자량의 펩타이드를 생산하였으며 평균 분자량을 GPC로 분석하였다 셀레늄 펩타이드의 glutathione peroxidase (GPx) 활성은 펩타이드의 분자량이 감소할수록 증가하였다. Sodium selenate은 sodium selenite에 비해 효모의 성장 저해를 적게 받았고 단백질 내 셀레늄 함량이 sodium selenite보다 높았다. 이 결과는 효모 배양에 의한 셀레늄 펩타이드의 생산의 가능성과 이를 이용한 항산화 제로서의 응용가능성을 보여주었다.

• BMB Reports
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• 제29권3호
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• pp.236-240
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• 1996

A 23-kDa molecular mass of antioxidant protein was purified from human liver. This protein exhibited the preventive effect against the inactivation of glutamine synthetase by a metal-catalyzed oxidation system. This antioxidant activity was supported by a thiol-reducing equivalent such as dithiothreitol in a similar manner to that of the 25-kDa thiol-specific antioxidant protein (TSA) from human red blood cells (HR). However, a thioredoxin-linked peroxidase activity of thiol-specific antioxidant protein of human liver (HLTSA) (0.91 ${\mu}mol/min/nmol$ of HLTSA) was much lower than that of thiol-specific antioxidant protein of human red blood cells (HRTSA) (16.4 ${\mu}mol/min/nmol$ of HRTSA). This HLTSA is also immnologically distinct from HRTSA Amino acid sequences of the three tryptic peptides (P1, P2, P3) of HLTSA were found to be completely homologous to segments of the known Mer5-like protein, which belongs to the known TSA family.

• Journal of Plant Biology
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• 제33권2호
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• pp.105-110
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• 1990

Physiological gradient of IAA-oxidizing enzyme activities was investigated in order to elucidate the mechanism of shoot differentiation in Cymbidium sp. (‘Jungfrau’) protocorms by using phenolic compounds (2, 4-dichlorophenol, catechol), auxin-inhibitors (PCIB, TIBA), and hormones (GA3, ABA, BA). The activity of IAA oxidase was decreased in protocorms treated with catechol decreased the catalytic activity of IAA oxidase or TIBA but this enzyme activity was increased after a temporary decrease at initial stages in the presence of 2, 4-dichlorophenol or PCIB. The activity of IAA oxidase in BA-treated protocorms (white and crown gall-like) was the highest of all. However, the catalytic activity of peroxidase increased after a temporary decrease at initial period. These results suggest that shoot differentiation and growth may be influenced by effective IAA levels in the protocorms causing IAA-oxidizing enzyme and phenolic compounds.

• 한국산림과학회지
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• 제81권3호
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• pp.234-246
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• 1992

조경수목(造景樹木)들의 대기오염물질(大氣汚染物質)들에 대한 감수성(感受性) 및 저항성(抵抗性)을 규명하기 위해서 야외조사(野外調査)와 실내실험(室內實驗)을 통하여 엽내(葉內) 유황함량(硫黃含量)과 peroxidase(POD) 및 superoxide dismutase(SOD) 함량(含量)을 측정(測定) 분석(分析)하였다. 은행나무에서는 엽내(葉內) 유황함량(硫黃含量)과 POD 활성간(活性間)에 부(負)의 상관(相關)이 나타났고 잣나무, 소나무 및 양버즘나무에서는 엽내(葉內) 유황함량(硫黃含量)과 POD 활성간(活性間)에 정(正)의 상관(相關)을 나타내었다. 각 수목(樹木)들은 오염물질(汚染物質)이 체내(體內)에 흡수(吸收), 축적(蓄積)됨에 따라 내성기구(耐性機構)로써 POD 같은 효소(酵素) 활성(活性)을 증가시켰다. 특히 잣나무와 양버즘나무의 POD 활성(活性)이 높게 나타났다, $SO_2$ 처리실험에서 고유의 POD 활성(活性)이 낮은 침엽수(針葉樹) 1년생 잎이나 은행나무에서는 $SO_2$ 처리구간에 POD 활성(活性) 변화가 거의 없으나, 고유의 POD 활성(活性)이 높은 스트로브잣나무와 튜립나무에서는 처리농도가 높을수록 POD 활성(活性)이 증가하는 것으로 보아, 외부 stress에 대한 단기적 POD 활성(活性)은 감수성(感受性)이 큰 수종(樹種)에서 나타나며, 장기적 POD 활성(活性) 증가는 식물체(植物體)의 방어기작(防禦機作)중의 일부로써 나타났으며 수목(樹木)의 SOD와 POD 활성간(活性間)의 상관관계(相關關係)는 은행나무에서만 부(負)의 상관(相關)을 보이고 나머지 수목(樹木)에서는 정(正)의 상관(相關)을 나타내었다. SOD와 POD 활성(活性)은 수종(樹種)마다 특이한 반응(反應)을 나타내며, 대부분의 수종(樹種)에서 SOD와 POD가 동시에 내성(耐性) 기구(機構)에 참여함을 알 수 있었다.

• BMB Reports
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• 제39권4호
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• pp.452-456
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• 2006

To elaborate the peroxidase activity of cytochrome c in the generation of free radicals from $H_2O_2$, the mechanism of DNA cleavage mediated by the cytochrome c/$H_2O_2$ system was investigated. When plasmid DNA was incubated with cytochrome c and $H_2O_2$, the cleavage of DNA was proportional to the cytochrome c and $H_2O_2$ concentrations. Radical scavengers, such as azide, mannitol, and ethanol, significantly inhibited the cytochrome c/$H_2O_2$ system-mediated DNA cleavage. These results indicated that free radicals might participate in the DNA cleavage by the cytochrome c and $H_2O_2$ system. Incubation of cytochrome c with $H_2O_2$ resulted in a time-dependent release of iron ions from the cytochrome c molecule. During the incubation of deoxyribose with cytochrome c and $H_2O_2$, the damage to deoxyribose increased in a time-dependent manner, suggesting that the released iron ions may participate in a Fenton-like reaction to produce $\cdot$OH radicals that may cause the DNA cleavage. Evidence that the iron-specific chelator, desferoxamine (DFX), prevented the DNA cleavage induced by the cytochrome c/$H_2O_2$ system supports this mechanism. Thus we suggest that DNA cleavage is mediated via the generation of $\cdot$OH by a combination of the peroxidase reaction of cytochrome c and the Fenton-like reaction of free iron ions released from oxidatively damaged cytochrome c in the cytochrome c/$H_2O_2$ system.