電気静的誘導を強化することで設計された,より速い超酸化物ディスミュータゼ変異体

E D Getzoff¹, D E Cabelli, C L Fisher

¹Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037.

Nature

|July 23, 1992

まとめ

銅,亜鉛超酸化物ディスミュータゼ (SOD) 酵素は,細胞を酸化的損傷から保護する. SODにおける静電誘導の強化

科学分野:

バイオケミストリーバイオケミストリー
酵素学酵素学とは
構造生物学構造生物学とは

背景:

銅,亜鉛超酸化物ディスミュータゼ (SOD) は,酸化的損傷から保護する重要な酵素です.
SODはスーパーオキシードラジカルを酸素と過酸化水素に変異させ,静電誘導によって強化された反応である.
人間のSODは,効率的なアクティブサイトメカニズムにより,急速な動力学 (Vmax ≈ 2 x 10^9 M-1 s-1) を表しています.

研究の目的:

SOD反応速度の向上における静電誘導の役割を調査する.
活性部位で正電荷を増やすことがSOD活動をさらに加速できるかどうかを判断する.
酵素における静電的に促進された拡散を最適化するための構造的要件を理解する.

主な方法:

人体SODのサイト固有の変異は,活性サイトの電荷分布を変化させる.
酵素反応速度とイオン強度依存度を測定するための動力学的測定法.
反応機構をモデル化するために静電相互作用を組み込むブラウンの動力学シミュレーション.

主要な成果:

陽性電荷を増やし,水素結合ネットワーク (Glu→Gln) を維持した変異体は,より速い反応率を示した.
これらの変異体は,シミュレーションと一致する,イオン強度依存性の増加を示した.
負荷逆転変異体 (Glu→Lys) は,負荷中和変異体よりも遅かったため,指向ネットワークの障害を示した.

結論:

SODにおける静電的に促進された拡散を最適化することは,標的型変異を生成することによって達成可能である.
アクティブサイトの静電ネットワークの構造的整合性を維持することは,酵素率を高めるために非常に重要です.
酵素の設計は,電荷,構造,拡散制限反応の相互作用を理解することで導かれる.

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