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首页> 外文期刊>Biochemistry >Glutamate Racemase Dimerization Inhibits Dynamic Conformational Flexibility and Reduces Catalytic Rates
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Glutamate Racemase Dimerization Inhibits Dynamic Conformational Flexibility and Reduces Catalytic Rates

机译：谷氨酸消旋酶二聚化抑制了动态构象灵活性并降低了催化速率

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Glutamate racemase (RacE) is a bacterial enzyme that converts L-glutamate to D-glutamate, annessential precursor for peptidoglycan synthesis. In prior work, we have shown that both isoforms cocrystallizenwith D-glutamate as dimers, and the enzyme is in a closed conformation with limited access to the active siten[May, M., et al. (2007) J. Mol. Biol. 371, 1219-1237]. The active site of RacE2 is especially restricted. Wenutilize several computational and experimental approaches to understand the overall conformationalndynamics involved during catalysis when the ligand enters and the product exits the active site. Our steerednmolecular dynamics simulations and normal-mode analysis results indicate that the monomeric form of thenenzyme is more flexible than the native dimeric form. These results suggest that the monomeric enzyme mightnbe more active than the dimeric form.We thus generated site-specific mutations that disrupt dimerization andnfind that the mutants exhibit significantly higher catalytic rates in the D-Glu to L-Glu reaction direction thannthe native enzyme. Low-resolution models restored from solution X-ray scattering studies correlate well withnthe first six normal modes of the dimeric form of the enzyme, obtained from NMA. Thus, along with the localnactive site residues, global domain motions appear to be implicated in the catalytically relevant structuralndynamics of this enzyme and suggest that increased flexibility may accelerate catalysis. This is a novelnobservation that residues distant from the catalytic site restrain catalytic activity through formation of thendimer structure.
机译：谷氨酸消旋酶（RacE）是一种细菌酶，可将L-谷氨酸转化为D-谷氨酸，这是肽聚糖合成的重要前体。在先前的工作中，我们显示了两种同工型都与D-谷氨酸共结晶为二聚体，并且该酶处于封闭构象中，与活性位点的通路有限[May，M。等人。 （2007）J.Mol。生物学371，1219-1237]。 RacE2的活性位点受到特别限制。 Wen利用几种计算和实验方法来理解当配体进入而产物离开活性位点时催化过程中涉及的总体构象动力学。我们的转向分子动力学模拟和正常模式分析结果表明，然后酶的单体形式比天然二聚体形式更具灵活性。这些结果表明单体酶可能比二聚体形式更具活性。因此，我们产生了破坏二聚化的位点特异性突变，发现该突变体在D-Glu到L-Glu反应方向上比天然酶具有更高的催化速率。从溶液X射线散射研究还原的低分辨率模型与从NMA获得的酶的二聚体形式的前六个正常模式密切相关。因此，连同局部活性位点残基，全局域运动似乎与该酶的催化相关的结构动力学有关，并且表明增加的柔性可以加速催化。这是一种新颖的观察，其远离催化位点的残基通过然后二聚体结构的形成抑制了催化活性。

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