ラサロシドAのバイオシンセシスにおけるポリエーテル形成のためのエポキシド水酸化物Lsd19:ポリエーテルバイオシンセシスにおけるポリエーレン-ポリエーポキシド仮説に関する直接的な実験的証拠
Yoshihiro Shichijo1, Akira Migita, Hiroki Oguri
1Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Journal of the American Chemical Society
|August 20, 2008
まとめ
研究者らは,ラサロシドなどのポリエーテル天然製品の形成に不可欠な酵素Lsd19を特定した. この研究は,ポリエーテル生物合成における酵素性エポキシド開口の最初の実験的証拠を提供し,6-エンド・テットサイクリング機構を明らかにしました.
科学分野:
- バイオケミストリー バイオケミストリー
- 自然製品のバイオシンセシス
- 酵素学 酵素学とは
背景:
- ポリエーテル代謝物は,複雑な構造を持つ重要な天然製品です.
- ポリエーテル骨格構造の背後にある酵素機構を理解することは,有機化学における重要な課題です.
- 酵素性ポリエーテル形成に関する実験データは不足しています.
研究 の 目的:
- ポリエーテル天然製品生物合成の酵素経路を解明する.
- ラサロシド形成における重要なサイクル化のステップに責任を持つ酵素を特定し,特徴づけること.
- ポリエーテル生物合成における酵素性エポキシド開口に関する最初の実験的証拠を提供すること.
主な方法:
- Escherichia coliのラサロシド生物合成遺伝子クラスターからの推定のエポキシドヒドロラーゼ遺伝子lsd19のクローン化と過剰発現.
- Lsd19酵素の浄化について.
- 提案された基板であるビセポキシプレラサロシドとその合成アナログを使用した酵素変換アッセイ.
- 比較のために,バイセポキシドをトリクロアセチン酸で化学処理する.
主要な成果:
- 精製されたLsd19酵素は,6-エンド・テットサイクリング方式でバイセポキシプレラサロシドをラサロシドAに成功裏に変換した.
- 合成されたアナログもLsd19によってその誘導体に変換され,その触媒活性が確認されました.
- 化学処理により,イソラサロシドAが5エクソテトサイクルによって生成され,酵素の特異なメカニズムが明らかになった.
- この研究は,バイセポキシプレラサロシドがバイオシンセティックの中間物質としての明確な証拠を提供します.
結論:
- 酵素Lsd19は,ラサロシド生物合成における連続的な循環エーテル形成を触媒化する.
- Lsd19は,エネルギー的に不利な6 - エンドーテットサイクリングを促進し,ポリエーテル形成における新しい発見です.
- この研究は,ポリエーテル天然製品につながる酵素性エポキシド開き反応の最初の実証を示しています.
- この発見は,複雑なポリエーテル天然製品の生物合成に関する重要な洞察を提供します.
関連する概念動画
Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
Structure and Nomenclature of Epoxides
Cyclic ethers are heterocyclic compounds with an oxygen atom in the ring along with carbon atoms. They are named depending on the number of carbon atoms present in their ring system. Cyclic ethers with a three-membered ring system are called “oxirane”, four-membered ring systems as “oxetane”, five-membered ring systems as “oxolane”, and six-membered ring systems as “oxane”. The cyclic structure of these rings imposes angle strain, and this strain is more in the ring having a smaller number of...


