Characterization of a metalloenzyme producing oxygen molecule from nitric oxide

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K22208
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 34:Inorganic/coordination chemistry, analytical chemistry, and related fields
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Tosha Takehiko 国立研究開発法人理化学研究所, 放射光科学研究センター, 専任研究員 (00548993)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 一酸化窒素 / 金属酵素 / 嫌気的メタン酸化 / 酸素発生

Outline of Final Research Achievements

On the basis of the proposal that a bacterium, Candidatus Methylomirabilis oxyfera, which obtains energy by anaerobic methane oxidation would have a protein catalyzing dismutation of nitric oxide (NO) by following reaction; 2NO → O2 + N2, putative NO dismutase (NOD) was expressed in Escherichia coli and was purified. Purified recombinant NOD showed intense absorption at the visible region, suggesting that NOD contains heme as expected from the fact that the amino acid sequence exhibits significant similarity to nitric oxide reductase (NOR) which has hemes. Although the similarity of the amino acid sequence to NOR, purified NOD showed no NO reduction activity. Proposed NO dismutase activity was not also detected for purified NOD.

Free Research Field

生物無機化学

Academic Significance and Societal Importance of the Research Achievements

NODにおいて提案されている一酸化窒素（NO）の不均化反応（2NO → O2 + N2）は、これまでに報告例のない生体内反応であり、その反応機構の理解は、生化学分野のみならず錯体化学・触媒化学分野など多くの研究分野において、ブレークスルーをもたらすと期待される。本研究では、NOD特有の機能を解析するまでにはいたらなかったが、NODタンパク質を組み換え体として発現させ精製することができた。本成果を土台として今後の研究が進むことで、NODの構造機能に関する理解が進み、新たなケミストリーが展開されることを期待したい。