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サイクロプロピルアミノ酸のバイオシンセシス中の非ヘム鉄酵素による神秘的な塩化

Frédéric H Vaillancourt¹, Ellen Yeh, David A Vosburg

¹Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.

|August 27, 2005

まとめ

研究者らは,CmaBとCmaCという新しい酵素を発見し,化合物を生物学的にハロゲン化して循環させます. この発見は,天然製品バイオシンセシスにおけるサイクロプロピル環の形成のための新しいメカニズムを明らかにしています.

科学分野:

バイオケミストリーバイオケミストリー
酵素学酵素学とは
自然製品のバイオシンセシス

背景:

4,000以上の天然製品には,生物合成中にハロゲン (塩素,ブロミン,ヨウ素) が含まれています.
ハロゲネーションは,これらの天然製品の生物活性に重大な影響を及ぼします.
活性化されていないアリファティック群のハロゲン化を触媒する酵素は,特徴づけられていなかった.

研究の目的:

コロナミック酸 (CMA) の生物合成に関与する新しい酵素を特徴づける.
CMA合成におけるサイクロプロパン環形成のメカニズムを解明する.
活性化されていないアリファティック群に作用する最初の知られているハロゲネーゼ酵素を特定する.

主な方法:

Pseudomonas syringaeの5つのタンパク質 (CmaA,CmaB,CmaC,CmaD,CmaE) の活性について調査しました.
CMA構造における酵素機能を決定するために生化学的分析を用いた.
CmaBを非ヘムFe (((2+),アルファケトグルタレート依存酵素,CmaCをサイクロプロパン形成酵素として特徴付けました.

主要な成果:

CmaBを同クラスで初めてハロゲナーゼ活性を示す酵素として特定し,特にガンマ位置でのl-アルロ-イソルエウシンを塩素化する.
CmaCが,ガンマ塩化中間物質からサイクロプロピル環の形成を触媒化することを実証した.
CmaBとCmaCが連続して作用することを確立した:ガンマハロゲン化に続いて分子内ガンマ除去.

結論:

CmaBとCmaCの結合作用は,ハロゲン化と除去によるサイクロプロパン環形成のための新しい生物学的戦略を表しています.
この研究は,これまで知られていなかった酵素を特徴づけ,ハロゲナーゼの多様性と機能の理解を広げています.
この発見は,コロナチンのような植物毒素の生物合成に関する洞察を提供します.

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