Cysteine SH and Glutamate COOH Contributions to [NiFe] Hydrogenase Proton Transfer Revealed by Highly Sensitive FTIR Spectroscopy

作者：Hulin Tai, Koji Nishikawa, Yoshiki Higuchi, Zong‐Wan Mao, Shun Hirota · 发表于：Angewandte Chemie International Edition · 年份：2019 · DOI：10.1002/anie.201904472 · 被引用次数：63 · 研究领域：Metalloenzymes and iron-sulfur proteins、Electrocatalysts for Energy Conversion、Ammonia Synthesis and Nitrogen Reduction

Abstract A [NiFe] hydrogenase (H2ase) is a proton‐coupled electron transfer enzyme that catalyses reversible H2 oxidation; however, its fundamental proton transfer pathway remains unknown. Herein, we observed the protonation of Cys546‐SH and Glu34‐COOH near the Ni–Fe site with high‐sensitivity infrared difference spectra by utilizing Ni‐C‐to‐Ni‐L and Ni‐C‐to‐Ni‐SIa photoconversions. Protonated Cys546‐SH in the Ni‐L state was verified by the observed SH stretching frequency (2505 cm−1), whereas Cys546 was deprotonated in the Ni‐C and Ni‐SIa states. Glu34‐COOH was double H‐bonded in the Ni‐L state, as determined by the COOH stretching frequency (1700 cm−1), and single H‐bonded in the Ni‐C and Ni‐SIa states. Additionally, a stretching mode of an ordered water molecule was observed in the Ni‐L and Ni‐C states. These results elucidate the organized proton transfer pathway during the catalytic reaction of a [NiFe] H2ase, which is regulated by the H‐bond network of Cys546, Glu34, and an ordered water molecule.