アミン触媒におけるエナミンの中間物質の直接観察
Xueyong Zhu1, Fujie Tanaka, Richard A Lerner
1Department of Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|December 9, 2009
まとめ
研究者らは,アルドラーゼ抗体の結晶構造に安定したエナミン中間物質を観察した. この発見は,タンパク質のアミン触媒は,これまで考えられていたよりも単純である可能性を示唆し,将来の触媒設計を導く.
科学分野:
- バイオケミストリー バイオケミストリー
- 構造生物学 構造生物学とは
- カタリシス カタリシス カタリシス
背景:
- エナミンの中間物質は,アルドラーゼやアミンの有機触媒などの生物学的触媒に不可欠です.
- 触媒におけるエナミンの中間物質の直接的な構造的証拠は,歴史的に稀であった.
- アルドラーゼ抗体は,新しい触媒メカニズムの可能性のある,エンジニアリングされた触媒です.
研究 の 目的:
- 触媒抗体のエナミン中間体を構造的に特徴付ける.
- エンジニアリングされたタンパク質におけるアミンベースの触媒の触媒機構を調査する.
- 新しい有機触媒およびバイオ触媒の合理的な設計のための洞察を提供すること.
主な方法:
- X線結晶学を用いて,アルドラーゼ抗体33F12.2の構造を決定した.
- 抗体は,1,3-ジケトン誘導体基板と複合体で結晶化されました.
- 構造分析は,エナミンの中間物質を特定し,特徴づけることに焦点を当てました.
主要な成果:
- アルドラーゼ抗体33F12.2の結晶構造に安定したエナミン中間物質が観察されました.
- この構造は,天然アルドラーゼと比較して,抗体内のアミン触媒の必須残基が少ないことを明らかにした.
- 抗体ポケットの水性環境は,エナミンの形成を促進します.
結論:
- 観察されたエナミン複合体は,抗体におけるエナミン触媒の直接的な構造的証拠を提供します.
- タンパク質におけるアミン触媒は,これまで考えられていたより複雑ではないかもしれない.
- これらの発見は,効率的なアミン有機触媒およびバイオ触媒の合理的な設計を導くでしょう.
関連する概念動画
Aldehydes and Ketones with Amines: Enamine Formation Mechanism
Enamine formation involves the addition of carbonyl compounds to a secondary amine through a series of reactions. The mechanism begins with the generation of carbinolamine, a nucleophilic attack followed by several proton transfer reactions. The hydroxyl group of the carbinolamine is converted into water to make a better leaving group that can push the reaction forward by eliminating a water molecule. In enamine formation, the last step involves the abstraction of a proton from the α carbon to...
Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview
Primary amines react with carbonyl compounds—aldehydes and ketones—to generate imines. Imines consist of a C=N double bond and are named Schiff bases after its discoverer—the German chemist Hugo Schiff. On the other hand, secondary amines react with carbonyl compounds to give enamines. In enamines, the presence of a C=C double bond adjacent to the nitrogen atom leads to the delocalization of the lone pair.
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines are useful synthetic intermediates where the lone pair on nitrogen is in conjugation with the C=C bond. They resemble enolate ions, as the resonance forms of both species have a nucleophilic α carbon.
Preparation of Amines: Reductive Amination of Aldehydes and Ketones
Carbonyl compounds and primary amines undergo reductive amination first to produce imines, followed by secondary amines in the same reaction mixture, using selective reducing agents like sodium cyanoborohydride or sodium triacetoxyborohydride. Reductive amination produces different degrees of substitution of amines depending on the starting amine substrate.
Amines to Amides: Acylation of Amines
Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...


