• Applied Biological Chemistry
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• 제48권2호
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• pp.115-119
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• 2005

DNA 모델 화합물인 bis(p-nitrophenyl)phosphate(BNPP)에 대한 2핵 닉켈(II) 착 화합물, ${\mu}-aquapentaaqua[{\mu}-3,6-bis(6'-methyl-2'-pyridyl)pyridazine]chlorodinickel(II)$ trichloride trihydrate(APNT)의 촉매 가수분해 반응성을 검토하였다. APNT의 산 해리 상수는 각각 $pKa_1=7.9$ 및 $pKa_2=9.6$이었으며 BNPP의 가수분해반응 결과, pH 7.0과 $50^{\circ}C$에서 무 촉매인 경우에 비하여 가수분해 속도를 약 37만 배 가량 촉진시킴을 확인하였다. 그리고 pH-rate profile로부터 실험 사실을 합리적으로 설명할 수 있는 APNT에 의한 BNPP의 촉매 가수분해 반응에 대한 일련의 catalytic cycle을 제안하였다. 따라서 반응의 각 단계에서 2핵 닉켈(II) 착 화합물의 금속 이온들은 phosphoryl group의 전달 속도를 촉진하였고 물 분자는 친핵체와 양성자 전달체로 작용하였다.

• Journal of Applied Biological Chemistry
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• 제49권3호
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• pp.86-89
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• 2006

The novel tetranuclear nickel (II) complex is a high rate accelerator in promoting hydrolysis of phosphate diesters. Nickel-bound bis-nitrophenyl phosphate (BNPP) can be $10^4$ times more reactive than the unbound BNPP. The large rate of enhancements by the complex slightly under basic condition has shown high catalytic activity in phosphate diester cleavage. The bell-shaped pH-rate profile indicated that the nickel-oxide form of the tetranuclear complex or its kinetic equivalent was the active species for cleaving BNPP. The catalytic hydrolysis between tetranuclear nickel (II) complex and phosphate diester proceeds via the formation of bidentate coordination of the anionic phosphate to the Ni (II) atom. This reveals that the complex has the possibility as artificial nuclease.

• 한국군사과학기술학회지
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• 제2권1호
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• pp.73-81
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• 1999

Four bis-iodosobenzoic acid derivatives have been synthesizd in 5 steps following literature methods from 5-hydroxyantranilic acid; 1) diazotization and iodination, 2) acid protection, 3) tosylate substitution, 4) acid deprotection, 5) oxidation of iodo-substituent to iodoso group. Catalytic effects of new 5,5'-tri-, tetra-, deca-, polyethyleneglycoxy- bis(2-iodosobenzoic acid) on hydrolysis reactions of PNPDPP(p-nitrophenyl diphenyl phosphate), sarin and soman have been measured to determine the role of ethyleneglycoxy substituents as phase transfer catalysts. At $25{\pm}0.2^{\circ}C$, pH 8.0, and cetyltrimethyl ammonium chloride(CTACl) micelle solution condition, bis-IBA derivatives hydrolyzes PNPDPP with maximum pseudo-first order rate constant($K_{obsd}^{max}$) of 0.32035 ~ 0.13659 $sec^{-1}$, which corresponds to 2~18 times rate increase than those of unsubstituted o-IBA[iodosobenzoate($K_{obsd}^{max}=0.0645sec^{-1}$), iodoxybenzoate ($K_{obsd}^{max}$ = $0.0178 sec^{-1}$)]. At the similar condition for PNPDPP hydrolysis, bis-IBA derivatives also act as efficient catalysts for hydrolytic cleavage of nerve agents such as sarin and soman. Hydrolysis rate constant with 5,5'-polyethyleneglycoxy- bis(2-iodosobenzoic acid) shows 7 times increase than that of simple 5-hydroxy-2-iodosobenzoic acid.

• BMB Reports
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• 제28권2호
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• pp.94-99
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• 1995

The properties of binding sites in the active site of $Zn^{2+}$-glycerophosphocholine cholinephosphodiesterase were examined using substrates and inhibitors of the enzyme. Phosphodiesterase hydrolyzed p-nitrophenylphosphocholine, p-aminophenylphosphocholine, and glycerophosphocholine, but did not hydrolyze either acylated glycerophosphocholine or bis (p-nitrophenyl)phosphate, suggesting a size limitation for interaction with a glyceryl moiety-binding subsite. The hydrolysis of p-nitrophenylphosphocholine was competitively inhibited by glycerophosphocholine and p-aminophenylphosphocholine, while glycerophosphoethanolamine was a weak inhibitor. The enzyme was also inhibited by choline, but not by ethanolamine. Thiocholine, a much more potent inhibitor than choline, was more inhibitory than cysteamine, suggesting a strict specificity of an anionic subsite adjacent to a $Zn^{2+}$ subsite. Of all oxyanions tested, the tellurite ion was found to strongly inhibit the enzyme by binding to a $Zn^{2+}$ subsite. The inhibitory role of tellurite was synergistically enhanced by tetraalkylammonium salts, but not by glycerol. Deactivation of the enzyme by diethylpyrocarbonate was partially protected by choline, but not by glycerophosphate. It is suggested that the active site of phosphodiesterase contains three binding subsites.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
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• pp.108-113
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• 1998

Egasyn is accessory protein of ${\beta}$-glucuronidase(${\beta}$-G) in the liver microsomes. Liver microsomal ${\beta}$-G is stabilized within the luminal site of the microsomal vesicles by complexation with egasyn which is one of carboxylesterase isozymes. We investigated the effects of organophosphorus compounds(OPs) such as insecticides on the dissociation of egasyn-${\beta}$-glucuronidase(EG) complex. The EG complex was easily dissociated by administration of OPs, i.e., Fenitrothion, EPN, Phenthionate, and bis-p-nitrophenyl phosphate(BNPP), and resulting ${\beta}$-G dissociated was released into blood, leading to the rapid and transient increase of plasma ${\beta}$-G level with a concomitant decrease of liver microsomal ${\beta}$-G level. In a case of phenthionate treatment, less increase in plasma ${\beta}$-G level was observed, as compared with those of other OPs. This may be explained by a fact that phenthionate was easily hydrolyzed by carboxylesterase. Similarly, carbamate insecticides such as Carbaryl caused rapid increase of plasma ${\beta}$-G level. In contrast, no significant increase of plasma ${\beta}$-G level was observed when pyrethroid insecticides were administered to rats. This is due to a fact that pyrethroids such as Phenthrin and Allethrin were easily hydrolyzed by A-esterase as well as carboxylesterase. On the other hand, addition of OPs to the incubation mixture containing liver microsomes caused the release of ${\beta}$-G from microsomes to the medium. From these in vivo and in vitro data, it is concluded that increase of the plasma ${\beta}$-G level after OPs administration is much more sensitive biomarker than cholinesterase inhibition to acute intoxication of OPs and carbamates.