• Parasites, Hosts and Diseases
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• 제47권4호
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• pp.421-424
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• 2009

Malaria parasites adapt to the oxidative stress during their erythrocytic stages with the help of vital thioredoxin redox system and glutathione redox system. Glutathione reductase and thioredoxin reductase are important enzymes of these redox systems that help parasites to maintain an adequate intracellular redox environment. In the present study, activities of glutathione reductase and thioredoxin reductase were investigated in normal and Plasmodium berghei-infected mice red blood cells and their fractions. Activities of glutathione reductase and thioredoxin reductase in P. berghei-infected host erythrocytes were found to be higher than those in normal host cells. These enzymes were mainly confined to the cytosolic part of cell-free P. berghei. Full characterization and understanding of these enzymes may promise advances in chemotherapy of malaria.

• BMB Reports
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• 제28권6호
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• pp.515-522
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• 1995

The effects of the thyroid hormone ($T_3$) on 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were evaluated in a baby hamster kidney cell line, C100. The cells cultured in MEM were supplemented with 10% thyroid hormone-depleted fetal bovine serum (THDS-MEM) and had a 82.5% lower level of HMG-CoA reductase activity than the cells grown in a medium supplemented with fetal bovine serum (FBS-MEM). When $T_3$ was supplemented to THDS-MEM, the reduction of the reductase activity was blocked in a dose-dependent manner. In the cells grown in THDS-MEM containing $T_3$ at a concentration of $10^{-6}$ M, the level of HMG-CoA reductase activity was 91.8% relative to the cells grown in FBS-MEM. These changes in HMG-CoA reductase activity seemed to be at least partly due to the changes of HMG-CoA reductase mRNA levels. The level of HMG-CoA reductase mRNA in cells incubated in THDS-MEM decreased to 76.2% relative to the cells grown in FBS-MEM, while the level of reductase mRNA in cells incubated in THDS-MEM containing $T_3$ at a concentration of $10^{-6}$ M increased to 243.4% relative to the cells grown in FBS-MEM. The increase of HMG-CoA reductase mRNA level after $T_3$ treatment may have been due to the increased stability of reductase mRNA, because the transcriptional rate of the reductase gene did not change significantly in the presence or absence of $T_3$. These results indicate that $T_3$ stabilizes HMG-CoA reductase mRNA at the posttranscriptional level and regulates HMG-CoA reductase activity in a dose-dependent manner.

• BMB Reports
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• 제28권1호
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• pp.17-20
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• 1995

Thioredoxin reductase is a flavoprotein oxidoreductase catalyzing the reduction of a cystine disulfide in thioredoxin. Thioredoxin, in turn, can reduce disulfide bonds in other proteins and serves as a reducing agent in enzymatic reactions such as those of ribonucleotide reductase and methionine sulfoxide reductase. In this work thioredoxin reductase was found to directly reduce DTNB in the absence of thioredoxin. This new reactivity of E. coli thioredoxin reductase was produced by relatively high concentrations of univalent cations such as $Na^+$, $K^+$, $Li^+$, and ${NH_4}^+$, and it appeared with the oxidation of NADPH. These results indicate that E. coli thioredoxin reductase may be slightly modified by univalent cations, and the modified enzyme directly reacts with DTNB. This DTNB-reducing activity offers a new assay method for E. coli thioredoxin reductase.

• 대한소아치과학회지
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• 제24권1호
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• pp.265-279
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• 1997

The purpose of this study was to do an epidemiological survey of the salivary reductase activity and dental caries prevalence of the large group of preschool children and analyze the validity of the salivary reductase activity test as a caries activity test. One thousand and forty-four preschool children were examined for caries experience and salivary reductase activity by dental survey and the Resazurin Disc Test. 39.8% of children showed low salivary reductase activity, 39.4% showed middle, and 20.8% showed high. Salivary reductase activity increased as age increased. All indexes of caries experience were high when salivary reductase activity was high. There was positive relation between salivary reductase activity and caries experience. The salivary reductase activity of children with no caries experience was lower than that of children with caries experience. The salivary reductase activity of children with low caries experience was lower than that of children with high caries experience. It seemed that the salivary reductase activity test had basic validity as a caries activity test. However, the test's ability to select the small risk group of high caries susceptibility should be enhanced.

• 한국식품영양과학회지
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• 제45권2호
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• pp.293-297
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• 2016

HMG-CoA reductase는 체내 콜레스테롤 생합성에 있어서 속도제한단계(율속) 효소이다. 본 연구는 HMG-CoA reductase에 대한 이소플라본 배당체의 저해 효과를 연구하였다. $100{\mu}M$의 농도에서 genistein-7-O-triglucoside(G2-genistin)는 HMG-CoA reductase 활성을 약 18% 정도 저해하였으나, daidzein-7-O-triglucoside는 저해 효과를 갖지 않았다. 시리아햄스터 HMG-CoA reductase의 반응속도 실험에서 G2-genistin은 농도에 관계없이 $V_{max}$의 저해 정도가 일정하였으며, 이것은 G2-genistin이 HMG-CoA reductase의 경쟁적 저해제로 작용함을 시사하고 HMG-CoA reductase의 활성을 직접적으로 저해함으로써 혈중 콜레스테롤 함량을 감소시킬 수 있음을 예상할 수 있다.

• Preventive Nutrition and Food Science
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• 제5권4호
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• pp.184-188
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• 2000

HMG-CoA reductase is th rate-limiting enzyme of cholesterol biosynthesis. As intracellular levels of cholesterol should be regulated elaborately in response to external stimuli an internal needs, the expression of the HMG-CoA reductase gene is regulated intricately at several different levels from transcription to post-translational modification. In this study, we investigated the regulatory mechanism of HMG-CoA reductase gene expression at the post-transcriptional/pre-translational levels in a baby hamster kidney cell line, C100. when 25-hydroxycholesterol was added to cells cultured in medium containing 5% delipidized fetal bovine serum and 25$\mu$M lovastatin, the levels of HMG-CoA reductase mRNA decreased rapidly, which seemed to be due to the increased degradation of reductase mRNA. These suppressive effects of 25-hydroxycholesterol on MG-CoA reductase mRNA levels were blocked by a translation inhibitor, cycloheximide. Similarly, actinomycin D and 5,6-dichloro-1-$\beta$-D-ribofuranosylbenzimidazole, transcription inhibitors, blocked the 25-hydroxycholesterol-mediated degradation of HMG-CoA reductase mRNA. These results indicate that new protein/RNA synthesis is required for the degradation of HMG-CoA reductase mRNA. In addition, data from the transfection experiments shows that cis-acting determinants, regulating the stability of reductase mRNA, were scattered in the sequence corresponding to 1766-4313 based on the sequence of Syrian hamster HMG-CoA reductase cDNA. Our data suggests that sterol-mediated destabilization of reductase mRNA might be one of the important regulatory mechanism of HMG-CoA reductase gene expression.

• Journal of Ginseng Research
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• 제20권1호
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• pp.106-110
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• 1996

The present study was undertaken to elucidate the effects of ginseng components on rat lens aldose reductase activity. Ginseng total saponin (GTS) exhibited inhibitory activities on rat lens aldose reductase in a dose-dependent manner. Among ginsenosides, Rf and Rgl showed potent inhibitory activities on rat lens aldose reductase. Lipid soluble fraction also inhibited rat lens aldose reductase activities. These data suggest that ginseng components inhibit rat lens aldose reductase activity in vitro.

• Toxicological Research
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• 제12권2호
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• pp.155-161
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• 1996

The enzymatic properties for NADPH-P450 reductase domain of a fusion protein between human cytochrome P450 1A1 and rat NADPH-P450 reductase expressed in Escherichia coli were investigated. The fusion plasmid pCW/1A1OR-expressed E. coli membrane showed high NADPH-cytochrome c reductase activity ($830.1\pm 85.8 nmol\cdot min^{-1}\cdot mg protein^{-1}$), while pCW control vector and P 450 1A1 expression vector pCW/1A1 showed relatively quite low activity ($4.35\pm 0.49, 3.27\pm 0.50 nmol\cdot min^{-1}\cdot mg protein^{-1}$, respectively). The kinetic curves for NADPH-cytochrome c reductase followed typical Michaelis-Menten kinetics. The $K_{max}$ and $V_{max}$ for NADPH-dependent reductase activity were $8.24\pm 2.61\mu $and $817.9\pm 60.8 nmol\cdot min^{-1}\cdot mg protein^{-1}$, respectively, whereas those for cytochrome c-dependent reductase activity were $19.97\pm 2.86\mu M$ and $1303.5\pm 67.1 nmol\cdot min^{-1}\cdot mg protein^{-1}$. The reductase activities were also compared with those of rat, porcine and human liver microsomes. The activity of pCW/ 1A1OR-expressed E. coli membrane was 15.2-fold higher than that of rat liver microsome. Treatment with benzo(a)pyrene, 7-ethoxyresorufin and $\alpha$-naphthofiavone which are known as specific substrates or inhibitor for human P450 1A1 increased NADPH-cytochrome c reductase activity of fusion protein in E. coli membrane dose-dependently. These results demonstrate that the membrane topology of fused enzyme may be important for activity of its NADPH-P450 reductase domain.

• Journal of Applied Biological Chemistry
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• 제51권6호
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• pp.302-306
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• 2008

국화과 식물인 민들레, 엉겅퀴, 그리고 고려엉겅퀴를 대상으로 항당뇨 활성 측정 방법 중 하나인 흰쥐 수정체 aldose reductase 저해 활성을 측정하였다. 여러 부위별 추출물 중 민들레 지상부 메탄올 추출물이 $IC_{50}\;8.71\;{\mu}g/mL$로서 뛰어난 저해 활성을 보였다. 국화과 식물에서 분리된 대표적인 화합물인 silymarin과 민들레에서 분리한 luteolin(1)그리고 고려 엉겅퀴에서 분리된 syringin(2)을 대상으로 aldose reductase저해 활성을 측정한 결과 silymarin과 luteolin은 뛰어난 aldose reductase 저해 활성을 보였다.

• Journal of Plant Biology
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• 제34권4호
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• pp.283-288
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• 1991

This work was carried out to determined the effect of 2,4-dinitrophenol(DNP) on in vivo nitrate reductase activity in the root of 6 day old rye (Secale cereale L.) seedlings. The nitrate reductase activity in the roots of 6 day old rye seedlings pretreated with 0.5 mM DNP was higher than that of the control group in all the experimental conditions. The optimal concentration of KNO3 for maximum nitrate reductase activity was 10 mM in both control and treated group. The nitrate reductase activity in the treatment of 10 mM KNO3 gradually increased for 4 h in both groups, and then maintained constantly. The nitrate reductase activity occurred per hour was highest at 1 h in both groups, while it was declined by large degrees as time goes on. The daily pattern of nitrate reductase activity was gradually decreased in both groups with the passage of day. The optimal pH for this experiment and a previous paper (Kwon et al., 1991), it was determined that the nitrate reductase activity in both roots and shoots of rye seedlings was increased by the treatment of 0.5 mM DNP, and particulary in both groups, the nitrate reductase activity in the roots of rye seedlings was higher than that in shoots of them.