• Applied Biological Chemistry
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• 제16권1호
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• pp.31-40
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• 1973

Azotobacter vinelandi의 세포추출물(細胞抽出物)들이 Shethna flavoprotein의 free radical 형(型)으로의 전자전달기구(電子傳達機構)에 관하여 연구(硏究)하였다. 전자전달(電子傳達)에 관여도(關與度)가 높은 단백질(蛋白質)로 황색형광성단백질(黃色榮光性蛋白質)(protein I)과 갈색단백질(褐色蛋白質)(protein II)을 정제(精製)하였고 이들은 $N_2$ 기압하(氣壓下) 또는 aceton-dry ice 동결(凍結)저장하에서도 쉽게 실활(失活)되었고 반응속도(反應速度) 역시 너무 완만하여 생체내반응(生體內反應)이기에는 의문점을 보였다. 한편 세포추출물중(細胞抽出物中)의 FMN은 NADH에 의(依)하여 환원이 쉽게 이루어졌으며, 환원형 $FMNH_2$는 비효소적(非酵素的)으로 Shethna flavoprotein 의 free radical 을 형성(形成)시켰으며 , 효소적반응속도(酵素的反應速度)보다 15배(倍)의 높은 반응속도(反應速度)를 보였다. 비록 FMN이 생체내(生體內)에서 타(他)단백질과 비결합형(非結合型)으로 존재(存在)하지 않는다해도 FMN의 전자전달체(電子電達體)의 가능성(可能性)을 제시(提示)하였다.

• Journal of Photoscience
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• 제9권2호
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• pp.98-101
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• 2002

Euglena gracilis abruptly changes its swimming direction after a sudden increase or decrease in incident light intensity, that is, step-up or step-down photophobic responses, resulting in photoavoidance or photoaccumulation, respectively. To identify the photoreceptor molecules for these UV-A/blue-light type photobehaviors, we purified a flavoprotein from isolated putative photosencory organelles (PFBs) of Euglena. The purified flavoprotein, which noncovalently bound flavin adenine dinucleotide (FAD), seemed to be a heterotetramer of alpha- and beta-subunits. Predicted amino acid sequences of each of the subunits were similar to each other and contained two FAD-binding domains each followed by an adenylyl cyclase catalytic domain. The purified flavoprotein actually showed adenylyl cyclase activity, being drastically elevated by blue-light irradiation. Suppression of gene expression of the flavoprotein (Photoactivated Adenylyl Cyclase, PAC) by RNA interference (RNAi) caused loss of the step-up photophobic response, demonstrating that PAC actually mediates photoavoidance of Euglena.

• Archives of Pharmacal Research
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• 제4권1호
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• pp.43-51
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• 1981

The effect of some alcohols on the riboflavin derivatives in non-polar solvent was studied by various spectroscopic method in order to support the view point that alcohol may directly interect with the isoalloxazine moiety of FAD, the coenzyme of D-amino-acid oxidase. The most possible association complex between alcohol and riboflavin is the 1:1 complex through the 2-C carbonyl function of the isollaxazine ring nd the hydroxyl proton of alcohol. It is appeared that methanol has a larger association constant than any other alcohols, and the association constant decreases with the carbon number increases and being bulkier in the alkyl group of alcohols.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권4호
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• pp.337-343
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• 2006

Trimethylamine dehydrogenase (TMADH, EC 1.5.99.7), an iron-sulfur flavoprotein that catalyzes the oxidative demethylation of trimethylamine to form dimethylamine and formaldehyde, was purified from Methylophaga sp. strain SK1. The active TMADH was purified 12.3-fold through three purification steps. The optimal pH and temperature for enzyme activity was determined to be 8.5 and $55^{\circ}C$, respectively. The $V_{max}\;and\;K_m$ values were 7.9 nmol/min/mg protein and 1.5 mM. A genomic DNA of 2,983 bp from Methylophaga sp. strain SK1 was cloned, and DNA sequencing revealed the open reading frame (ORF) of the gene coding for TMADH. The ORF contained 728 amino acids with extensive identity (82%) to that of Methylophilus methylotrophus $W_3A_1$.

• Journal of Microbiology and Biotechnology
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• 제21권5호
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• pp.464-469
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• 2011

The arsH gene is one of the arsenic resistance system in bacteria and eukaryotes. The ArsH protein was annotated as a NADPH-dependent flavin mononucleotide (FMN) reductase with unknown biological function. Here we report for the first time that the ArsH protein showed high ferric reductase activity. Glu104 was an essential residue for maintaining the stability of the FMN cofactor. The ArsH protein may perform an important role for cytosolic ferric iron assimilation in vivo.

• BMB Reports
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• 제31권5호
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• pp.444-452
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• 1998

The visible spectra of soybean ferric leghemoglobin reductase exhibited a charge transfer band at 530 nm under aerobic condition. Spectra of the oxidized enzyme show a flavin peak at 454 nm and the enzyme has three redox states associated with the active site of the enzyme. The enzyme has an active disulfide bridge and two-electron transfer may dominate in the ferric state of leghemoglobin reduction. The midpoint potentials of the enzyme were determined by spectrotitration to be -0.294 V for disulfide/dithiol and -0.318 V for FAD/$FADH_2$. Since the midpoint potentials for $NAD^+$/NADH and the ferrous/ferric states of leghemoglobin are -0.32 V and +0.22 V, respectively, it is proposed that two electrons are transferred sequentially from NADH to FAD, to the disulfide group, and then to the ferric state of leghemoglobin in the enzyme reaction.

• 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.

• 한국미생물·생명공학회지
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• 제24권5호
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• pp.579-584
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• 1996

The molecular weight of the purified nucleoside oxidase estimated by gel filtration column chromatography was 480,000 and the enzyme protein was composed of four nonidentical subunits (81,000, 69,000, 32,000 and 16,000). On the basis of the visible absorption spectra and the enzymatic determination of the purified enzyme, the enzyme was supposed as a hemoprotein and also a flavoprotein containing 3 moles of FAD per I mole of enzyme. The isoelectric point of the enzyme was pH 5.1. Addition of metal salts such as 1 mM SnCl$_{2}$ and PbCl$_{2}$ into an enzyme reaction solution inhibited the enzyme activity by 94 and 90%, respectively. The enzyme activity was also lost significantly by hemoenzyme inhibitors such as NaCN and NaN$_{3}$ and flavoenzyme inhibitor, acriflavine and quinacrine. The maximal nucleoside oxidase activity was observed at pH 7.0 and 55$\circ$C. The nucleoside oxidase was relatively stable in the range of pH 5.5-9.0 and below 55$\circ$C.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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• pp.161.1-161.1
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• 2003

NAD(P)H:quinone oxidoreductase (quinone reductase: QR: EC1.6.99.2), a cytosolic FAD-containing flavoprotein, form one of the important component of the phase II drug-metabolizing enzyme systems. It is found in all mammalian species tested and is expressed in many organs including the liver. QR catalyses two-electron reduction of qui nones to hydroquinones thereby suppresses the formation of superoxide anion radical. (omitted)

• 한국균학회지
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• 제17권3호
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• pp.161-168
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• 1989

표고버섯(L. edodes) 중의 mitochondria는 설탕밀도단계기울기법에 따라 분리정제 하였다. 앞서 보고한 바와 같이, 각 파장별 빛조사(400-700nm)에 따른 mitochondrial ATPase와 ATP synthase의 활성도는 680nm와 470nm에서 각각 활성화되었다. 본 연구에서, 400nm 이하의 파장별 빛조사에 따른 mitochondrial ATPase 및 ATP synthase의 활성도는 380nm와 330nm에서 각각 활성화되었으며, 330nm 및 350에서 각각 억제되었다. FAD의 존재하에서, mitochondrial ATP synthase는 활성화 파장 및 억제 파장의 조사에 의하여 활성도가 각각 증가된 반면, mitochondrial ATPase의 활성도는 감소되었다. 그러나, NADH의 존재하에서, 이들 파장의 조사에 의한 효소의 활성도는 변화가 없었다. 또한, 두 효소는 각각의 활성화 파장 및 억제 파장이 조사됨에 따라 $FADH_2$를 FAD로 산화시키는 spectrum을 보였다. 이로써, 이 두 효소는 빛 조사에 의하여 생체내의 산화 환원반응의 산화제로 작용하였으며, 특히 mitochondrial ATP synthase의 활성화에 따른 광유발물질은 mitochondria 중에 존재하는 flavin 또는 flavoprotein으로 추정된다.