Fig. 4.

Comparisons of electrocatalytic H₂ oxidation and H⁺ reduction for WT CrHydA1 and variants E141D^CrHydA1 (red) and E144D^CrHydA1 (blue) from pH 5 to pH 9 (A–E, respectively), presented after normalizing to the H₂ oxidation current recorded at an H₂ oxidation overpotential of 0.25 V. Note that relative current densities do not reflect absolute enzyme activities. The crossing point of the dashed lines represents the 2H⁺/H₂ thermodynamic potential. Experimental conditions as for Fig. 3.