Lysine, Arginine, and Histidine Residues in Peptide-Catalyzed Hydrogen Evolution at Mercury Electrodes
Involvement of hexapeptides composed of lysine (Lys(6)), arginine (Arg(6)) or histidine (His(6)) in the catalytic hydrogen evolution reaction (CHER) was studied. Using McIlvaine buffer, we changed the concentration of citric acid (proton donor in the CHER) either (a) by changing the buffer concentration at constant pH or (b) by changing the pH at constant buffer concentration. These two approaches showed almost the same catalytic behavior of Lys(6) and Arg(6) but strikingly different ones in the case of His(6). The results suggested that at neutral pH His residue is much weaker catalyzer than those of Lys or Arg.