細菌の酸化窒素還元酵素による生物学的N2O生成の構造的基礎
Tomoya Hino1, Yushi Matsumoto, Shingo Nagano
1RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
まとめ
Pseudomonas aeruginosaの酸化窒素還元酵素 (NOR) の結晶構造は,サイトクロム酸化酵素と異なるユニークな触媒二核センターを明らかにします. この発見は,酸化窒素 (N2O) の生産を理解するために極めて重要です.
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
- 酵素学 酵素学とは
背景:
- 酸化窒素還元酵素 (NOR) は,鉄を含む酵素である.
- NORは,酸化窒素 (NO) を温室効果ガスである酸化窒素 (N2O) に還元する触媒である.
研究 の 目的:
- Pseudomonas aeruginosaからのNORの結晶構造を決定するために.
- 触媒双核センターの構造的詳細を解明する.
主な方法:
- X線結晶グラフィーです.
- 2.7アンストームの解像度でタンパク質構造の決定
主要な成果:
- Pseudomonas aeruginosa NORの結晶構造が決定されました.
- 触媒双核センターが解明され,ヒームでない鉄 (Fe(B)) がHisとGluリガンドによって調整されていることが示されました.
- サイトクローム酸化酵素 (COX) で発見された重要なHis-Tyr共性結合は,NOR.では存在しない.
- COXで観察された陽子経路 (D-およびK-経路) は,NORで発見されなかった.
結論:
- NORのユニークな構造的特徴,特にHis-Tyr結合と特定の陽子経路の欠如は,その触媒的機能にとって重要である.
- NOR反応に不可欠な陽子は,細胞外環境から採取される可能性が高い.
関連する概念動画
Inorganic Nitrogen Assimilation
Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
Microbes and the Nitrogen Cycle
The nitrogen cycle is a complex biogeochemical process critical to maintaining the balance of nitrogenous compounds in ecosystems. This cycle involves multiple microbial-mediated transformations through which nitrogen changes oxidation states, supporting essential ecological functions and contributing to plant and microbial growth.Nitrogen Fixation and AmmonificationNitrogen fixation initiates the cycle by converting inert atmospheric nitrogen (N₂) into bioavailable ammonia (NH₃), a process...
Overview of Nitrogen Metabolism
Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of ammonia, ammonium ions, nitrate, nitrite, or nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
Oxidation and Reduction of Organic Molecules
Energy production within a cell involves many coordinated chemical pathways. Most of these pathways are combinations of oxidation and reduction reactions, which occur at the same time. An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation and reduction usually occur together, these pairs of reactions are called redox reactions.
The removal of an electron from a molecule, results in a...
The removal of an electron from a molecule, results in a...
Nitric Oxide Signaling Pathway
Nitric oxide (NO), an inorganic gas, acts as a potent second messenger in most animal and plant tissues. NO diffuses out of the cells that produce it and enters the neighboring cells to generate a downstream response. NO synthase (NOS) catalyzes NO production by the deamination of the amino acid arginine. There are three isoforms of NOS. Endothelial cells have endothelial NOS (eNOS), nerve and muscle cells have neuronal NOS (nNOS), and macrophages produce inducible NOS (iNOS) upon exposure to...
Metabolism of Chemolithotrophs
Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation. However, because inorganic electron donors...


