两个阿斯巴达酸盐之间共享的低屏障质子作为一个变形开关,改变β-乳酸酶BlaC的基质特异性
Jing Sun1, Aimee L Boyle1, Steffen Brünle2
1Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, the Netherlands.
International journal of biological macromolecules
|August 12, 2024
概括
在Mycobacterium tuberculosis BlaC中的谷氨酸残留物对于水解ceftazidime并非必不可少. 高 pH 诱导 BlaC 中的构造转换,增强 ceftazidime 的水解并改变基质的特异性.
科学领域:
- 生物化学 生化学
- 酶学 是一种酶学.
- 结构生物学 结构生物学
背景情况:
- 血清β-乳酸酶是通过化和脱化对β-乳酸抗生素进行水解的酶.
- 脱氧化步骤通常涉及一种保存的谷氨酸残留物激活水分子.
- 结核菌Mycobacterium的BlaC酶显示了ceftazidime的低水解,但P167S突变体由于扩大的活性位点口袋而表现出增强的活性.
研究的目的:
- 通过野生型BlaC和Glu166Ala突变物来研究保存的谷氨酸 (Glu166) 在脱氧化塞夫塔齐迪姆的作用.
- 描述野生型BlaC的pH依赖性行为及其构造状态.
- 了解 BlaC 中基质特异性的转变的结构基础.
主要方法:
- 在各种pH值下,酶动力学测定使用野生型BlaC和BlaC E166A突变体.
- 酶状态和形状变化的表征.
- 在活性部位内的结相互作用的分析.
主要成果:
- Glu166显著增强了对尼特洛塞芬的BlaC活性,但不增强对塞夫塔齐的活性,这证实了其在塞夫塔齐脱氧化中的非必不可少的作用.
- 野生型BlaC存在于高pH的两个状态,其中一个状态表现出明显更快的ceftazidime水解,类似于P167S突变.
- 关闭和开放的BlaC构造之间的pH依赖切换是由Asp172和Asp179.9之间的低屏障键的破坏介导的.
结论:
- 保存的谷氨酸残留物不需要通过BlaC去基化他胺.
- BlaC可以经历pH诱导的形状变化,改变其基质特异性,特别是对于ceftazidime.
- 蛋白质结构的微妙变化,例如键的破坏,很容易导致酶基质特异性的转变.
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