• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Molecular Biology >Destabilization of the homotetrameric assembly of 3-deoxy-d-arabino- heptulosonate-7-phosphate synthase from the hyperthermophile pyrococcus furiosus enhances enzymatic activity
【24h】

Destabilization of the homotetrameric assembly of 3-deoxy-d-arabino- heptulosonate-7-phosphate synthase from the hyperthermophile pyrococcus furiosus enhances enzymatic activity

机译：嗜热嗜热球菌的3-脱氧-d-阿拉伯-庚酸七磷酸酯合酶的同四聚体装配的不稳定增强酶活性

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Many proteins adopt homomeric quaternary structures to support their biological function, including the first enzyme of the shikimate pathway that is ultimately responsible for the biosynthesis of the aromatic amino acids in plants and microorganisms. This enzyme, 3-deoxy-d-arabino-heptulosonate-7- phosphate synthase (DAH7PS), adopts a variety of different quaternary structures depending on the organism in which it is found. The DAH7PS from the hyperthermophilic archaebacterium Pyrococcus furiosus was previously shown to be tetrameric in its crystalline form, and this quaternary association is confirmed in an improved structure in a different crystal system. This tetramer is also present in solution as revealed by small-angle X-ray scattering and analytical ultracentrifugation. This homotetrameric form has two distinct interfaces, both of which bury over 10% each of the surface area of a single monomer. Substitution of Ile for Asp in the hydrophobic region of one interface gives a protein with a remarkable 4-fold higher maximum catalytic rate than the wild-type enzyme. Analytical ultracentrifugation at pH 7.5 reveals that the tetrameric form is destabilized; although the protein crystallizes as a tetramer, equilibrium exists between tetrameric and dimeric forms with a dissociation constant of 22 μM. Thus, under the conditions of kinetic assay, the enzyme is primarily dimeric, revealing that the dimeric form is a fully functional catalyst. However, in comparison to the wild-type protein, the thermal stability of the dimeric protein is significantly compromised. Thus, an unusual compromise of enzymatic activity versus stability is observed for this DAH7PS from an organism that favors a hyperthermophilic environment.
机译：许多蛋白质采用同源的四级结构来支持其生物学功能，包括the草酸酯途径的第一个酶，该酶最终负责植物和微生物中芳香族氨基酸的生物合成。这种酶3-脱氧-d-阿拉伯糖基庚酸七磷酸酯合酶（DAH7PS），根据所发现的生物体而采用多种不同的四级结构。先前已证明，来自嗜热嗜热球菌的DAH7PS以晶体形式为四聚体，并且在不同晶体系统中以改进的结构证实了这种四级缔合。该四聚体也存在于溶液中，如小角度X射线散射和分析超速离心所揭示。该四聚体形式具有两个不同的界面，每个界面都掩埋单个单体表面积的10％以上。在一个界面的疏水区中用Ile取代Asp产生的蛋白质的最大催化速率比野生型酶高出4倍。在pH 7.5下进行的超离心分析表明，四聚体形式不稳定。尽管蛋白质结晶为四聚体，但四聚体和二聚体形式之间存在平衡，解离常数为22μM。因此，在动力学测定的条件下，该酶主要是二聚体，表明该二聚体形式是全功能催化剂。然而，与野生型蛋白质相比，二聚体蛋白质的热稳定性显着受损。因此，从有利于超嗜热环境的生物体中观察到该DAH7PS的酶活性相对于稳定性的不寻常的折衷。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号