Pang Siew Siew, Duggleby Ronald G, Guddat Luke W
Centre for Protein Structure Function and Engineering, Department of Biochemistry and Molecular Biology, School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
J Mol Biol. 2002 Mar 22;317(2):249-62. doi: 10.1006/jmbi.2001.5419.
Acetohydroxyacid synthase (AHAS; EC 4.1.3.18) catalyzes the first step in branched-chain amino acid biosynthesis. The enzyme requires thiamin diphosphate and FAD for activity, but the latter is unexpected, because the reaction involves no oxidation or reduction. Due to its presence in plants, AHAS is a target for sulfonylurea and imidazolinone herbicides. Here, the crystal structure to 2.6 A resolution of the catalytic subunit of yeast AHAS is reported. The active site is located at the dimer interface and is near the proposed herbicide-binding site. The conformation of FAD and its position in the active site are defined. The structure of AHAS provides a starting point for the rational design of new herbicides.
乙酰羟酸合酶（AHAS；EC 4.1.3.18）催化支链氨基酸生物合成的第一步。该酶的活性需要硫胺素二磷酸和黄素腺嘌呤二核苷酸（FAD），但后者的存在出人意料，因为该反应不涉及氧化或还原。由于其在植物中的存在，AHAS是磺酰脲类和咪唑啉酮类除草剂的作用靶点。在此，报道了酵母AHAS催化亚基分辨率为2.6埃的晶体结构。活性位点位于二聚体界面，靠近推测的除草剂结合位点。确定了FAD的构象及其在活性位点中的位置。AHAS的结构为新型除草剂的合理设计提供了一个起点。
