大腸菌[NiFe]型ヒドロゲナーゼによる水素活性化機構の解析
Hyd-1, a membrane-associated [NiFe]-hydrogenase from Escherichia coli, reversibly oxidizes molecular H2 at an active site containing one Ni and one Fe atom. Conserved residues Arg509, Asp118, and Asp574 form an outer-shell canopy above the metals, while Glu28 occupies the opposite face of the active site. Site-directed mutagenesis was used to probe the catalytic base responsible for H2 cleavage and to map proton-transfer pathways. Although canopy residues were previously assumed to be purely structural, the R509K substitution—which leaves the overall architecture nearly intact—reduces catalytic activity by more than 100-fold. Variants carrying substitutions at one or both aspartate residues retain substantial activity. Based on these findings, a frustrated Lewis pair (FLP)-like mechanism is proposed: H2 undergoes heterolytic cleavage through simultaneous polarization by the metal center acting as the Lewis acid and the nitrogen of Arg509 acting as the Lewis base.
H2 undergoes heterolytic cleavage via a frustrated Lewis pair (FLP)-like mechanism in which the metal center (Lewis acid) and the nitrogen of Arg509 (Lewis base) simultaneously polarize the H2 molecule, facilitating bond splitting at the [NiFe] active site.
This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).
See also:
https://h2-papers.org/en/papers/27284053