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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 42, Number 3
JKCSEZ 42(3)
June 20, 1998 

Interaction of Barley Acetolactate Synthase with Triazolopyrimidine Inhibitors

Triazolopyrimidine계 저해제와 보리 Acetolactate Synthase와의 상호작용
Jae-Soeb Lee, Soo-Ik Chang, Sung-Keon Namgoong, Jung-Hyu Shin, Jung-Do Choi

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 IC50값은 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.

Acetolactate synthase (ALS) is the common enzyme in the biosynthesis of branched chain amino acids, Val, Leu, and Ile in bacteria, yeast, and higher plants. The enzyme is target site of several classes of structually diverse herbicides, including the sulfonylureas, the imidazolinones, the triazolopyrimidines, and the primidyl-oxy-benzoates. We have synthesized new triazolopyrimidine (TP) derivatives, and determined their inhibitory activities on barley ALS. lC51 values for the active compounds were 3.2 nM-0.62 mM, and some of them appeared to be potent inhibitors. The progress curves for inhibition of ALS by TP4, a representative derivative, indicated that the extent of inhibition increased with incubation time. The inhibition of ALS by TP4 showed mixed-type inhibition with respect to pyruvate. Dual inhibition analyses of TP4 versus imidazolinone Cadre and feedback inhibitor Leu suggested that three different classes of inhibitors bind to ALS in a mutually exclusive manner. Chemical modification of tyrosyl residues of ALS decreased sensitivity of ALS to TP4, while modification of tryptophan and cysteine did not affect the sensitivity.

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