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首页> 外文期刊>Biochemistry >Mechanism of enolase: the crystal structure of asymmetric dimer enolase-2-phospho-D-glycerate/enolase-phosphoenolpyruvate at 2.0 A resolution
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Mechanism of enolase: the crystal structure of asymmetric dimer enolase-2-phospho-D-glycerate/enolase-phosphoenolpyruvate at 2.0 A resolution

机译：烯醇化酶的机理：不对称二聚体烯醇化酶-2-磷酸-D-甘油/烯醇化酶-磷酸烯醇丙酮酸的晶体结构，分辨率为2.0 A

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摘要

Enolase, a glycolytic enzyme that catalyzes the dehydration of 2-phospho-d-glycerate (PGA) to form phosphoenolpyruvate (PEP), is a homodimer in all eukaryotes and many prokaryotes. Here, we report the crystal structure of a complex between yeast enolase and an equilibrium mixture of PGA and PEP. The structure has been refined using 29 854 reflections with an F/sigma(F) of >/=3 to an R of 0.137 with average deviations of bond lengths and bond angles from ideal values of 0.013 A and 3.1 degrees , respectively. In this structure, the dimer constitutes the crystallographic asymmetric unit. The two subunits are similar, and their superposition gives a rms distance between Calpha atoms of 0.91 A. The exceptions to this are the catalytic loop Val153-Phe169 where the atomic positions in the two subunits differ by up to 4 A and the loop Ser250-Gln277, which follows the catalytic loop Val153-Phe169. In the first subunit, the imidazole side chain of His159 is in contact with the phosphate group of the substrate/product molecule; in the other it is separated by water molecules. A series of hydrogen bonds leading to a neighboring enolase dimer can be identified as being responsible for ordering and stabilization of the conformationally different subunits in the crystal lattice. The electron density present in the active site suggests that in the active site with the direct ligand-His159 hydrogen bond PGA is predominantly bound while in the active site where water molecules separate His159 from the ligand the binding of PEP dominates. The structure indicates that the water molecule hydrating carbon-3 of PEP in the PEP --> PGA reaction is activated by the carboxylates of Glu168 and Glu211. The crystals are unique because they have resolved two intermediates on the opposite sides of the transition state.
机译：烯醇化酶是一种催化2-磷酸-d-甘油酸（PGA）脱水形成磷酸烯醇丙酮酸（PEP）的糖酵解酶，在所有真核生物和许多原核​​生物中都是同型二聚体。在这里，我们报告酵母烯醇酶与PGA和PEP的平衡混合物之间的复合物的晶体结构。使用29 854次反射（F / sigma（F）> / = 3到R = 0.137）对结构进行了改进，键长和键角的平均偏差分别偏离理想值0.013 A和3.1度。在这种结构中，二聚体构成晶体学不对称单元。两个亚基相似，它们的叠加使Calpha原子之间的均方根距离为0.91A。例外是催化环Val153-Phe169，其中两个亚基中的原子位置相差最多4 A，而环Ser250- Gln277，遵循催化环Val153-Phe169。在第一个亚基中，His159的咪唑侧链与底物/产物分子的磷酸基团接触;在另一个中，它被水分子隔开。可以确定导致相邻的烯醇化酶二聚体的一系列氢键负责晶格中构象上不同的亚基的排序和稳定。活性部位中存在的电子密度表明，在具有直接配体-His159氢键的活性部位中，PGA主要被结合，而在水分子将His159与配体分开的活性部位中，PEP的结合占主导。结构表明，PEP→PGA反应中PEP的碳水合碳水-3被Glu168和Glu211的羧酸盐活化。晶体之所以独特，是因为它们在过渡态的相反两侧解析了两个中间体。

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