Figure 5. Hydrogenase activity assays.

Enzymatic activity was assayed both in the direction of hydrogen evolution and hydrogen uptake at pH 8.0 with 10 mM methyl viologen as electron mediator, showing that C298D causes an equal decrease in the reaction rate for both reactions. Relative activity was calculated as the ratio with wild type activity (H₂ evolution: 230±6 µmol H₂ min⁻¹ mg protein⁻¹; H₂ uptake: 433±7 µmol H₂ min⁻¹ mg protein⁻¹).