Time‐Resolved Crystallography of the Reaction Intermediate of Nitrile Hydratase: Revealing a Role for the Cysteinesulfenic Acid Ligand as a Catalytic Nucleophile |
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| Authors: | Dr Yasuaki Yamanaka Dr Yuki Kato Dr Koichi Hashimoto Dr Keisuke Iida Prof Kazuo Nagasawa Dr Hiroshi Nakayama Dr Naoshi Dohmae Prof Keiichi Noguchi Prof Takumi Noguchi Prof Masafumi Yohda Prof Masafumi Odaka |
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| Institution: | 1. Department of Biotechnology and Life Science, Graduate School of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184‐8588 (Japan);2. Division of Material Science, Graduate School of Science, Nagoya University, Furo‐cho, Chikusa‐ku, Nagoya 464‐8602 (Japan);3. Global Research Cluster Collaboration Promotion Unit, RIKEN, 2‐1, Hirosawa, Wako‐shi, Saitama 351‐0198 (Japan);4. Instrumentation Analysis Center, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184‐8588 (Japan);5. Department of Life Science, Faculty and Graduate School of Engineering and Resource Science, Akita University, Akita City, Akita 010‐8502 (Japan) |
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| Abstract: | The reaction mechanism of nitrile hydratase (NHase) was investigated using time‐resolved crystallography of the mutant NHase, in which βArg56, strictly conserved and hydrogen bonded to the two post‐translationally oxidized cysteine ligands, was replaced by lysine, and pivalonitrile was the substrate. The crystal structures of the reaction intermediates were determined at high resolution (1.2–1.3 Å). In combination with FTIR analyses of NHase following hydration in H218O, we propose that the metal‐coordinated substrate is nucleophilically attacked by the O(SO?) atom of αCys114‐SO?, followed by nucleophilic attack of the S(SO?) atom by a βArg56‐activated water molecule to release the product amide and regenerate αCys114‐SO?. |
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| Keywords: | cysteinesulfenic acid nitrile hydratase reaction intermediates reaction mechanisms time‐resolved X‐ray crystallography |
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