带有正电荷的活性位点组的静电相互作用是否会收紧酶性酸转移的过渡状态?
Ivana Nikolic-Hughes1, Douglas C Rees, Daniel Herschlag
1Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
Journal of the American Chemical Society
|September 24, 2004
概括
酸酸酶 (AP) 催化显示了与硫酸和酸水解类似的过渡状态,表明活性部位的静电效应最小. 这一发现澄清了酶反应机制.
科学领域:
- 生物化学 生化学
- 酶学 是一种酶学.
- 化学动力学 化学动力学
背景情况:
- 讨论了酶性酸转移机制,特别是静电相互作用在过渡状态上的作用.
- 性酸酶 (AP) 是一种关键的酶,催化酸的水解.
研究的目的:
- 调查静电相互作用在酸酸酶催化酶酸转移期间对过渡状态特征的影响.
- 为了比较酸和酸的过渡状态,在AP活性部位的解反应.
主要方法:
- 利用线性自由能量关系 (LFER) 来分析酶反应动力学.
- 通过测量k(cat) /K(M) 来确定布伦斯特德系数β (lg),用于一系列硫酸乙烯单基底.
- 与获得的布伦斯特德系数进行比较,并将其与之前报告的酸酸乙烯二基底的值进行比较.
主要成果:
- 发现AP催化硫酸和酸水解的布伦斯特德系数非常相似 (-0.76 +/- 0.14和 -0.77 +/- 0.10,分别).
- 这些相似的值表明,尽管基板电荷有差异,但两种基板类型的过渡状态都可比较.
- 鉴定出效应是导致确定布伦斯特德系数不确定性的因素.
结论:
- 酸和硫酸盐水解反应在酸酸酶活性部位的过渡状态似乎是相同的.
- 活性点的静电相互作用对这些反应的过渡状态内的电荷分布有微不足道的影响.
- 这项研究提供了对酶催化过程中静电和固态因素微妙相互作用的见解.
相关概念视频
Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Electrochemical Systems
Electrochemical systems provide a fascinating insight into the dynamic interplay of charged species within various phases. One notable example is the interaction between a membrane permeable to K⁺ ions but not to Cl⁻ ions, separating an aqueous KCl solution from pure water. As K⁺ ions diffuse through the membrane, they generate net charges on each phase, leading to a potential difference between them.Similarly, when a piece of Zn is immersed in an aqueous ZnSO₄ solution, the Zn metal, composed...
The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
Transition State Theory
Transition-state theory, also known as activated-complex theory, provides a molecular-level explanation of reaction rates in both gas-phase and solution-phase reactions. It extends earlier kinetic models by considering the formation of a short-lived, high-energy configuration during a reaction.The progress of a chemical reaction can be represented using a reaction profile, which plots potential energy against the reaction coordinate. As two reactant molecules approach one another, their...


