選択的に化学性オートロフィックの原始的および可逆的なTCAサイクル
Takuro Nunoura1, Yoshito Chikaraishi2,3,4, Rikihisa Izaki5
1Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. takuron@jamstec.go.jp.
まとめ
この研究では,新種の可逆性トリカルボキシル酸 (TCA) サイクルがThermosulfidibacter takaii*で発見されました. この古代の炭素固定経路はシトラート合成を用いており,従来の TCA 還元サイクルモデルに挑戦しています.
科学分野:
- 微生物学
- 生物化学
- 天体生物学
背景:
- 還元性三炭酸 (rTCA) 循環は,地球上の生命にとって不可欠な古代の炭素固定経路です.
- 炭素固定の進化とメカニズムを理解することは,初期の生命と潜在的地球外生命を理解する鍵です.
研究 の 目的:
- 深層に枝分かれするケモリソトロフィック細菌* ABI70S6Tの炭素固定経路を調査する.
- この生物におけるトリカルボキシル酸 (TCA) 循環のメカニズムと進化的意義を解明する.
主な方法:
- 代謝遺伝子を特定するゲノム分析
- 酵素の機能と調節を決定する酵素測定法
- 異なる成長条件下で代謝中間物質を分析するための代謝プロファイリング.
主要な成果:
- テルモスルフィディバクタータカイで以前は知られていなかった可逆性TCAサイクルを発見した.
- TCAサイクルの方向が利用可能な炭素源によって制御されていることを示す.
- ATP依存のシトラート分裂を回避した化学自給状態下でのrTCAサイクルを駆動する重要な酵素として,シトラート合成酵素 (CS) の特定.
結論:
- *Thermosulfidibacter takaii*のrTCAサイクルは,従来のモデルとは異なる形で,シトラート合成剤を介して逆方向に動作する.
- この可逆的なCSメカニズムは,rTCAサイクルの祖先の形態を表す可能性があります.
- この発見は,選択的に生命のケモリトミクストロフィック起源の可能性を示唆している.
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