オスラート,マロナート,アセトアセテート,オスラロアセテートデカルボキシラーゼが直面する運動的な課題
Richard Wolfenden1, Charles A Lewis, Yang Yuan
1Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, United States. water@med.unc.edu
Journal of the American Chemical Society
|March 26, 2011
まとめ
酵素は反応を劇的に加速する. 触媒化されていないオキシラートデカルボキシル化は非常に遅いので,オキシラートデカルボキシラーゼのような酵素が生物学的過程の速度を大幅に高めることを示しています.
科学分野:
- バイオケミストリー バイオケミストリー
- 酵素の動力学について
- 化学反応の速度は化学反応の速さです.
背景:
- 酵素は生物学的触媒として作用し,反応速度を大幅に増加させます.
- 触媒化されていない反応を理解することは,酵素の効率を定量化するために極めて重要です.
研究 の 目的:
- 酵素の触媒力を非触媒反応と比較する.
- オキシラートデカルボキシラーゼによって提供される速度の上昇を決定するために.
主な方法:
- アリファ酸の高温での非触媒デカルボキシル化の速度を決定する.
- 反応速度を25°Cの標準温度まで引き算する.
- 反応メカニズムに対するコファクター (O(2),Mn(II)) の影響を調査する.
主要な成果:
- pH4.2でのオキサラートの非触媒解炭酸化率は1.1 × 10(-12) s(-1) であった.
- オキシラートデカルボキシラーゼは,推定2.5 × 10 〜 13 倍の速度向上を提供します.
- 触媒化されていないオキサラートデカルボキシル化は,O2とMn2から独立しており,ヘテロリティックな除去が示唆される.
結論:
- 酵素は,非触媒反応と比較して,速度を大幅に改善します.
- オキサラートのデカルボキシル化は,アンカタライズされたときと,酵素によって触媒化されたときのメカニズムが異なります.
関連する概念動画
Loss of Carboxy Group as CO2: Decarboxylation of β-Ketoacids
Carboxylic acids, upon heating, undergo a decarboxylation reaction by releasing carbon dioxide gas. Monocarboxylic acids do not undergo decarboxylation easily. However, a silver salt of carboxylic acid reacts with bromine or iodine under high temperature to release carbon dioxide gas and forms halide with one less carbon. This reaction is called the Hunsdiecker reaction.
Loss of Carboxy Group as CO2: Decarboxylation of Malonic Acid Derivatives
Just like β-keto acids—which upon thermal decarboxylation form ketones—β-dicarboxylic acids undergo decarboxylation to generate monocarboxylic acids with the liberation of carbon dioxide.
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...
Pyruvate Oxidation
After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
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...


