Hydrogen molecules can modulate enzymatic activity and structural properties of pepsin in vitro.

Hydrogen gas therapy has been recognized as the promising application merit. However, the underlying mechanism on the biological effects remains far from being understood. In this work, pepsin used as a research model, the effects of hydrogen-rich water on the protein activities and structural properties were investigated by enzymatic assay, atomic force microscopy-based peakforce quantitative nanomechanical mapping (PF-QNM) and terahertz time-domain spectroscopy (THz-TDS). We found that hydrogen-rich water can increase the protein activity and its apparent height while alter the mechanical properties (Young's modulus) and the terahertz dynamics. These results suggest a possible mode of hydrogen molecules acting with pepsin through the local changes of hydrophobic interfaces in the protein molecules, thus provide the first evidence for the direct interaction between hydrogen with proteins and a biophysical insight into the mechanism of hydrogen as well as other gases on the biological effects.