阿尔代氧降解酶对乙甲的减半反应:一个联合的QM/MM研究
Sebastian Metz1, Dongqi Wang, Walter Thiel
1Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany.
Journal of the American Chemical Society
|March 18, 2009
概括
化氧化还原酶在其还原性半反应中使用谷氨酸 (Glu869) 作为易斯基催化剂. 这种质子转移增强了基质活动,使化物转移成为速度决定的步骤.
科学领域:
- 生物化学 生物化学
- 计算化学计算化学
- 酶的机制 酶的机制
背景情况:
- 化氧降解酶对代谢过程至关重要.
- 了解其还原性半反应机制是酶功能的关键.
- 之前的研究缺乏详细的机制性见解.
研究的目的:
- 为了阐明化氧化还原酶的还原性半反应的催化机制.
- 研究谷氨酸 (Glu869) 在催化中的作用.
- 为了确定反应中的速度决定性步骤.
主要方法:
- 结合量子力学/分子力学 (QM/MM) 的计算研究.
- 探索五种不同的反应途径.
- 对Glu869.9的基质结合模式和质子化状态的分析.
主要成果:
- 确定了一条有利的途径,Glu869作为易斯基,去质子化氧化基.
- 通过Glu869进行的质子转移增强了核友性和电友性,增加了酶活性.
- 反应分为两个阶段进行:核友性攻击,其次是化物转移,证实了两电子氧化过程.
- 一种具有桥接水分子的变体显示了类似的能量障碍.
- Glu869主要降低核友性攻击屏障,使化物转移速率决定.
结论:
- Glu869的催化作用对阿尔代氧化还原酶的高活性至关重要.
- 减少性半反应涉及协调的核友性攻击和化物转移.
- 化物转移是整体还原性半反应中决定速度的步骤.
相关概念视频
Oxidations of Aldehydes and Ketones to Carboxylic Acids
Oxidation of aldehydes and ketones results in the formation of carboxylic acids. Aldehydes, bearing hydrogen next to the carbonyl group, are easily oxidized compared to ketones. This is because an aldehydic proton can easily be abstracted during oxidation.
Aldehydes readily undergo oxidation in strong oxidizing agents such as potassium permanganate and chromic acid. The oxidation can also be carried out using mild oxidizing agents such as silver oxide. In fact, aldehydes can be easily oxidized...
Aldehydes readily undergo oxidation in strong oxidizing agents such as potassium permanganate and chromic acid. The oxidation can also be carried out using mild oxidizing agents such as silver oxide. In fact, aldehydes can be easily oxidized...
Oxidation of Alcohols
In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:
The process of oxidation in a chemical reaction is observed in any of the three forms:
Reactions of Aldehydes and Ketones: Baeyer–Villiger Oxidation
Baeyer–Villiger oxidation converts aldehydes to carboxylic acids and ketones to esters. The reaction uses peroxy acids or peracids and is often catalyzed by acid. The reaction is named after its pioneers, Adolf von Baeyer and Victor Villiger. The reaction is achieved by a wide range of peracids such as m-chloroperoxybenzoic acid (mCPBA), perbenzoic acid (C6H5COOOH), peracetic acid (CH3COOOH), hydrogen peroxide (H2O2), and tert-butyl hydroperoxide (t-BuOOH).
The carbonyl center is activated by...
The carbonyl center is activated by...
Acid Halides to Alcohols: LiAlH4 Reduction
Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
Aldehydes and Ketones with Alcohols: Hemiacetal Formation
Similar to water, alcohols can add to the carbonyl carbon of the aldehydes and ketones. The addition of one molecule of alcohol to the carbonyl compound forms the hemiacetal or half acetal. As depicted below, in a hemiacetal, the carbon is directly linked to an OH and OR group.
Crossed Aldol Reaction Using Weak Bases
This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it slowly to a mixture of formaldehyde and weak bases like hydroxide and alkoxide. Upon slow addition of the aldehyde, the base deprotonates the α carbon of the aldehyde to form the corresponding enolate. The enolate subsequently attacks the formaldehyde to form a single crossed product. Figure 1 depicts the aforementioned reaction.


