• BMB Reports
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• 제28권3호
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• pp.265-270
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• 1995

Acetolactate synthase (ALS, EC 4.1.3.18) is the first common enzyme in the biosynthesis of leucine, isoleucine, and valine. It is the target enzyme for several classes of herbicides, including the sulfonylureas, the imidazolinones, the triazolopyrimidines, the pyrimidyl-oxy-benzoates and the pyrimidyl-thio-benzens. The sulfonylurea-resistant ALS gene (SurB) from Nicotiana tabaccum [Lee et al. (1988) The EMBO J. 7, 1241-1248] was cloned into the bacterial expression plasmid pT7-7. The resulting recombinant plasmid pT7-ALS was used to transform an ALS-deficient Escherichia coli strain MF2000. MF2000 cells transformed with pT7-ALS grew in the absence of valine and isoleucine. ALS activities of 0.042 and 0.0002 ${\mu}mol/min/mg$ protein were observed in the crude extracts prepared from MF2000 cells transformed with plasmids pT7-ALS and pT7-7, respectively. In addition, the former crude extract containing mutant ALS was insensitive to inhibition by K11570, a new chemical class of herbicides. $IC_{50}$ values for K11570 were $0.13{\pm}0.01$ mM. For comparison, a plasmid pTATX containing the wild-type Arabidopsis thaliana ALS coding sequences was also expressed in MF2000. ALS activities of 0.037 ${\mu}mol/min/mg$ protein were observed, and the wild type ALS was sensitive to two different classes of herbicides, K11570 and ALLY, a sulfonylurea. $IC_{50}$ values for K11570 and ALLY were $0.63{\pm}0.07$ and $80{\pm}5.6$ nM, respectively. Thus, the results suggest that the sulfonylurea-resistant tobacco ALS was functionally expressed in the bacteria, and that K11570 herbicides bind to the regulatoty site of ALS enzymes.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1153-1157
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• 2011

A kinetic study is reported for aminolysis of S-4-nitrophenyl X-substituted thiobenzoates 3a-g in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Thiol esters 3a-g are 7.8-47.6 fold more reactive than the corresponding oxygen esters (i.e., 4-nitrophenyl X-substituted benzoates 1a-g). Such reactivity order appears to be in accordance with the expectation that 4-nitrothiophenoxide in 3a-g is a better nucleofuge than 4-nitrophenoxide in 1a-g since the former is 2.64 pKa units less basic than the latter. Hammett plot for the reactions of 3a-g exhibit poor correlation coefficients ($R^2$ = 0.977-0.986) with negative deviation by substrates possessing an electrondonating group (EDG), while the Yukawa-Tsuno plots result in excellent linear correlation ($R^2$ = 0.995-0.997) with ${\rho}$ = 0.93-1.23 and r = 0.57-0.67, indicating that the negative deviation shown by substrates possessing an EDG is caused by ground-state stabilization through resonance interactions but not due to a change in ratedetermining step upon changing the nonleaving-group substituent X. The ${\rho}$ value increases as the incoming amine becomes more basic and more reactive, indicating that the RSP is not operative in the current reactions.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2241-2247
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• 2007

A new series of chiral bent-shaped liquid crystals with an asymmetric central core based on 1,6- dihydroxynaphthalene and chiral terminal chain prepared from (S)-(?)-2-methyl-1-butanol, 1,6-naphthalene bis[4-(4-alkoxyphenyliminomethyl)]benzoates [N(1,6)-n-O-PIMB(n-2)*-(n-4)O (n = 8-11)] were synthesized. Their mesomorphic properties and phase structures were investigated by means of electro-optical, polarization reversal current, and second harmonic generation measurements in order to confirm the relationship between the molecular structure and phase structure. All odd n (n = 9 and 11) compounds, N(1,6)-9-O-PIMB7*-5O and N(1,6)-11-O-PIMB9*-7O exhibit antiferroelectric phase, whereas even n (n = 8 and 10) compounds was flexible, N(1,6)-10-O-PIMB8*-6O exhibits the ferroelectric phase but N(1,6)-8-O-PIMB6*-4O exhibits the antiferroelectric phase. These results come from the decrease of the closed packing efficiency within a layer and the lack of uniform interlayer interaction between adjacent layers, which were caused by the asymmetrical naphthalene central core. Thus, we concluded that the structure of central core as well as the terminal chain plays an important role for the emergence of particular polar ordering in phase structures.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2410-2414
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• 2014

A kinetic study is reported on nucleophilic substitution reactions of Y-substituted-phenyl picolinates (7a-7h) with a series of cyclic secondary amines in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Comparison of the kinetic results with those reported previously for the corresponding reactions of Y-substituted-phenyl benzoates (1a-1f) reveals that 7a-7h are significantly more reactive than 1a-1f. The Br${\o}$nsted-type plot for the aminolysis of 4-nitrophenyl picolinate (7a) is linear with ${\beta}_{nuc}=0.78$, which is typical for reactions proceeding through a stepwise mechanism with expulsion of the leaving group being the rate-determining step. The Br${\o}$nsted-type plots for the piperidinolysis of 7a-7h and 1a-1f are also linear with ${\beta}_{lg}=-1.04$ and -1.39, respectively, indicating that the more reactive 7a-7h are less selective than the less reactive 1a-1f to the leaving-group basicity. One might suggest that the enhanced reactivity of 7a-7h is due to the inductive effect exerted by the electronegative N atom in the picolinyl moiety, while the decreased selectivity of the more reactive substrates is in accord with the reactivity-selectivity principle. However, the nature of intermediate (e.g., a stabilized cyclic intermediate through the intramolecular H-bonding interaction for the reactions of 7a-7h, which is structurally not possible for the reactions of 1a-1f) is also responsible for the enhanced reactivity with a decreased selectivity.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2929-2933
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• 2010

Pseudo-first-order rate constants ($k_{obsd}$) have been measured for nucleophilic substitution reactions of 2-pyridyl benzoate 5 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol. The plots of $k_{obsd}$ vs. $[EtOM]_o$ are curved upwardly but linear in the excess presence of 18-crown-6-ether (18C6) with significant decreased $k_{obsd}$ values in the reaction with EtOK. The $k_{obsd}$ value for the reaction of 5 with a given EtONa concentration decreases steeply upon addition of 15-crown-5-ether (15C5) to the reaction medium up to ca. [15C5]/$[EtONa]_o$ = 1, and remains nearly constant thereafter, indicating that $M^+$ ions catalyze the reaction in the absence of the complexing agents. Dissection $k_{obsd}$ into $k_{EtO^-}$- and $k_{EtOM}$, i.e., the second-order rate constants for the reaction with the dissociated $EtO^-$ and the ion-paired EtOM, respectively has revealed that ion-paired EtOM is 3.2 - 4.6 times more reactive than dissociated $EtO^-$. It has been concluded that $M^+$ ions increase the electrophilicity of the reaction center through a 6-membered cyclic transition state. This idea has been examined from the corresponding reactions of 4-pyridyl benzoate 6, which cannot form such a 6-membered cyclic transition state.

• 대한화학회지
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• 제35권1호
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• pp.90-95
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• 1991

할로벤질 할라이드의 선택적 카르보닐화에 대한 방법을 검토하였다. 알킬(알콕시메틸)벤조에이트는 한 반응기에서 두 반응에 의해 완성되며, 일차로 알코올 용매하에서 알콕시 음이온을 할로벤질 할라이드와 반응시키면, 알킬 할로벤질 에테르가 Williamson ether 합성법에 의해 얻어진다. 이차로 Na$_2$CO$_3$, CH$_3$I 및 Co$_2$(CO)$_8$을 첨가하고, 일산화탄소 기류하에서 반응시키면, 알릴할라이드 부분이 카르보닐화되어 알킬(알콕시메틸)벤조에이트를 높은 수득률로 얻을 수 있었다.

• Journal of Applied Biological Chemistry
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• 제65권4호
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• pp.299-306
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• 2022

In this study, derivatives of trimethoxybenzene were investigated as inhibitors of melanogenesis. We examined the effects of methyl 3,4,5-trimethoxybenzoate (MTB), ethyl 3,4,5-trimethoxybenzoate (ETB), methyl 3,4,5-trimethoxycinnamate (MTC), and ethyl 3,4,5-trimethoxycinnamate (ETC). First, the inhibitory effects of these agents on melanin production were evaluated using α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells. We found that all derivatives decreased α-MSH-induced melanin production in B16F10 melanoma cells; ETC showed a strong inhibitory effect at half of the concentration of the other derivatives. As tyrosinase is considered a key enzyme of melanogenesis, we also examined whether the derivatives inhibited tyrosinase activity. MTC and ETC reduced mushroom tyrosinase activity and expression levels of α-MSH-induced B16F10 cellular tyrosinase protein. Inhibitory effects of all derivatives on α-MSH-induced B16F10 cellular tyrosinase activity were shown in a dose-dependent manner. Additionally, the derivatives were exposed to diphenylpicrylhydrazyl free radical to examine their antioxidant characteristics. All derivatives showed considerable antioxidant activity, which was 2-fold higher than that of arbutin. In conclusion, the trimethoxybenzene derivatives, including MTB, ETB, MTC, and ETC exerted anti-melanogenic and antioxidant effects on α-MSH-stimulated melanogenesis, demonstrating their potential for use as novel hypopigmenting agents and antioxidants.

• 대한화학회지
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• 제42권3호
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• pp.306-314
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• 1998

Acetolactate synthase(ALS)는 박테리아, yeast, 그리고 고등 식물에서 가지를 가진 아미노산 Val, Leu, Ile의 생합성에 공통적으로 관여하는 필수적인 효소이다. 최근에 개발된 sulfonylurea, imidazolinone, triazolopyrimidine, 그리고 pyrimidyl-oxy-benzoate계 제초제들은 구조적으로 상호 유사성이 없음에도 불구하고 모두 ALS를 작용 표적으로 한다. Triazolopyrimidine(TP)계의 새로운 유도체들을 합성하여 보리의 ALS에 대해 저해활성을 측정하였다. 활성을 나타낸 저해제들의 $IC_{50}값은 3.2nM-0.62mM로 몇 개의 유도체는 뛰어난 활성을 보였다. 보리 ALS에 대해 triazolopyrimidine 유도체 TP4의 저해활성은 반응 시간이 증가함에 따라 증가하였고, 혼합형 저해유형을 보여주었다. TP4와 imidazolinone 제초제인 Cadre, 그리고 feedback 저해제인 Leu에 대한 dual inhibition 실험 결과 모두 평행한 kinetic pattern이 얻어져 이들 저해제의 결합 부위가 최소한 부분적으로 중복되는 부분이 있음을 시사했다. ALS의 Tyr의 변형은 TP4에 의한 저해 효과를 감소시키는 반면 Trp과 Cys 변형은 TP4의 결합에 영향을 나타내지 않았다.

• 한국응용곤충학회지
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• 제43권1호
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• pp.43-48
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• 2004

2000년 8월 충남 부여의 장미 재배지에서 채집한 점박이응애가 etoxazole에 대해 3,700배의 저항성을 나타내었다. 이 집단을 실내에서 3년 동안 etoxazole로 100회 이상 도태하여 5,000,000배 이상의 저항성계통을 얻었다. 이 계통은 약제처리 없는 조건 하에서 1년 이상 경과된 후에도 암컷 성충의 etoxazole에 대한 저항성 수준은 변화가 없었다. 이 저항성계통의 유전과 교차저항성 유무를 조사하였다. 감수성계통 수컷과 저항성계통 암컷을 상호 교배( $R_{♂}$${\times}$ $S_{♂}$)하여 얻은 $F_1$과 $F_2$의 우성도는 각각 0.98과 0.98로 완전우성이었으며, $S_{♀}$${\times}$ $R_{♂}$으로 상호 교배하여 얻은 $F_1$과 $F_2$의 우성도는 각각 -0.97과 -0,68로 불완전열성이었다. 따라서 etoxazole저항성을 지배하는 유전인자는 수컷보다 암컷성충에 의존하여 완전우성에 의해 지배되는 것으로 나타났다. 이 저항성 성충은 acequinocyl과 emamectin benzoate에 대해 각각 10.4배와 14.0배의 교차저항성을 나타내었고, 알은 milbemectin, amitraz, pyridaben에 대해 각각 52.0배, 14.6배, 9.4배의 교차저항성을 나타내었다. 한편 카바제이트계 살비제인 bifenazate에 대해서는 역상관 교차저항성을 나타내었으므로, etoxazole에 저항성을 보이는 농가에서는 bifenazate를 교호살포하면 점박이응애를 효율적으로 방제할 수 있을 것이다

• 대한화학회지
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• 제43권4호
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• pp.461-468
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• 1999

Acetolactate synthase (ALS)는 가지를 가진 필수아미노산 Val, Leu, Ile의 생합성 과정에서 공통적으로 작용하는 효소이다. ALS는 서로 구조적 유사성이 없는triazolopyrimidine, imidazolinone,sulfonylurea, 그리고 pyrimidyl-oxy-benzoate 제초제들의 공통적인 작용 표적이다. 보리로부터 부분 정제한 ALS를 이용하여 새로이 합성한 triazolopyrimidine sulfonamide 유도체들의 저해 활성을 측정하였다. 활성을 가진 유도체들의 $IC_{50}$ 값은 0.5nM∼8${\mu}M$ 범위였으며, 그 중에서 탁월한 저해 활성을 갖는 것은 TP1과TP2 유도체로 $IC_{50}$ 값은 각각 0.5 nM과 1.6 nM이였다. 이 저해제들은 기존의 상품화된 제초제인 Metosulam ($IC_{50}$;3.6 nM), Flumetsulam ($IC_{50}$;126 nM), 그리고 Cadre ($IC_{50};4 {\mu}M$)에 비해 보리 ALS에 대한 저해 활성이 보다 우수하였다. 보리 ALS에 대한 TP2의 저해 활성은 반응시간이 증가함에 따라 증가하였고, 혼합형 저해 유형을 보였다. TP2와 imidazolinone 계열의 제초제인 Cadre, 그리고 되먹임(feedback) 저해제인 Leu에 대한 이중저해 (dual inhibition) 실험 결과 TP2와 Cadre의 경우는 평행한 반응속도론적 형태가 그러나 TP2와 Leu의 경우는 한 점에서 만나는 반응속도론적 헝태가 얻어졌다. 이는 TP2와 Cadre의 결합 부위가 최소한 부분적으로 중복되고 있음을 시사한다. Cys 잔기에 대한 화학적 변형은 TP2와 Cadre의 결합에는 영향을 미치지 않으나, Leu의 결합에는 영향을 미쳤다.