Investigation into the regulation of the directionality of the reversible redox reaction induced by a conformational dynamics of the enzyme-substrate complex

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K07304
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Structural biochemistry
• Research Institution: Kanazawa University
• Principal Investigator: SEO DAISUKE 金沢大学, 物質化学系, 助教 (10339616)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: フラボ酵素 / フェレドキシン / 酸化還元反応 / 酵素反応速度論 / フラビン / NADPH / NADH

Outline of Final Research Achievements

The redox reaction catalyzed by FNR is thermodynamically reversible. But under the physiological conditions the direction is optimized toward either NAD(P)+ reduction or NAD(P)H oxidation. This research aims to reveal the regulative mechanism of the directionality of the reversible redox reaction in the context of structure-function relation based on kinetic and structure analyses approaches. Kinetic analyses of the reactions between bacterial FNRs and NADP+/H revealed that the difference in the conformation of the reduced FAD altered the rate limiting step of the NADP+ reduction reaction, indicating that the residues interacting with reduced FAD play an important roles in the regulation of the directionality. The mutation on the residues in the C-terminal region affected the stabilization of the CT complex, leading an effective hydride transfer and optimization of the redox equilibrium between FNR and NADP+/H, thus contributing to the regulation of the directionality.

Free Research Field

酵素学

Academic Significance and Societal Importance of the Research Achievements

相同性は高いが生理的に要求される反応方向が異なるFNRを用いた比較研究により，これまで酸化還元平衡に基づき説明されていたFNRの触媒反応の方向性が，実際には基質結合と酸化還元状態の変化に伴う構造変化による制御を受けており，構造的にも正逆方向で異なる過程をたどることが確認された．この結果は，FAD/NAD(P)H依存型酵素の構造－機能相関に基づく反応機構の理解の礎を築くと共に，フラボ酵素の反応方向制御における還元型FADのコンホメーションの制御の重要性を新たに提示するものである．