メナキノン生物合成:アミノフタロシンの形成には,独特の SAM 酵素のラジカルが必要です
Nilkamal Mahanta1, Dmytro Fedoseyenko, Tohru Dairi
1Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
Journal of the American Chemical Society
|October 3, 2013
まとめ
研究者らは,新しい酵素であるアミノフタロシン合成酵素 (MqnE) を特定し,それはバクテリアのメナキノン (ビタミンK2) 生物合成に不可欠である. この急進的なSAM酵素は,新しい反応を触媒化し,この重要なビタミンに関する理解を深める.
科学分野:
- バイオケミストリー バイオケミストリー
- 微生物学 微生物学とは
- 酵素学 酵素学とは
背景:
- メナキノン (MK,ビタミンK2) は,細菌の電子伝送,哺乳類の血液凝固,骨代謝に不可欠です.
- *Streptomyces coelicolor*におけるMKのための新しい生物合成経路は,コリスマートのアミノフタロシンへの変換を含む.
- この変換に責任を持つ酵素は,MqnAに加えて,未確認のままでした.
研究 の 目的:
- メナキノン生物合成経路に欠けている酵素を特定し,特徴づけること.
- 特定された酵素の触媒機構を解明する.
- ラジカルSAMスーパーファミリー内の酵素反応の新奇性を探求する.
主な方法:
- アミノフタロシン生物合成経路の再構成 in vitro.
- 特定された酵素の生化学的特徴,MqnE.
- ラジカルSAM酵素アッセイを用いた反応機構の分析.
主要な成果:
- アミノフタロシン合成酵素 (MqnE) は,欠落した酵素として特定されました.
- MqnEは,アデノシルラジカルを3-[(1-カルボキシビニル) オキシ]ベンゾ酸に添加するSAM酵素である.
- これは,急進的なSAM酵素スーパーファミリーのこれまで未知の反応型を表しています.
結論:
- MqnEとその新しい触媒機構の発見は,メナキノン生物合成の理解を大幅に前進させる.
- この発見は, SAM 酵素の急進によって触媒化された反応の既知のレパートリーを拡張します.
- 特徴づけられた経路は,潜在的なバイオテクノロジーの応用のための新しいターゲットを提供します.
関連する概念動画
Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
The Electron Transport Chain
The electron transport chain or oxidative phosphorylation is an exothermic process in which free energy released during electron transfer reactions is coupled to ATP synthesis. This process is a significant source of energy in aerobic cells, and therefore inhibitors of the electron transport chain can be detrimental to the cell's metabolic processes.
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q in...
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q in...
Radical Formation: Elimination
Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. For example, as depicted in Figure 1, dibenzoyl peroxide yields a pair of unstable radicals upon homolysis. Given its instability, this radical spontaneously undergoes elimination via a C–C bond cleavage to form a relatively more stable phenyl radical. The mechanism involves cleavage of the bond between the α and β positions with respect to...
Electron Transport Chain: Complex I and II
The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
ROS generation is regulated and maintained at moderate levels necessary...
Biosynthesis of Nucleic Acids
Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. This pathway maintains a balanced nucleotide pool, preventing imbalances that could jeopardize genetic integrity and cellular function. Given the crucial role of nucleotides, their synthesis is tightly regulated to ensure proper cellular homeostasis.Purine BiosynthesisThe biosynthesis of purine nucleotides begins with ribose-5-phosphate, a...
Radical Formation: Addition
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...


