Figure 6. Hercynine’s deuterium exchange with D₂O when EanB_Y353F2Tyr variant is used as the catalyst and MetC using selenocystine as the selenium source.

(A) Time course of the [ε-D]-hercynine formation under multiple turn-over conditions. The reaction mixture contained 50 μM of EanB_Y353A, EanB_WT, or 12.5 μM EanB_Y353F2Tyr variant. (B) Hercynine’s deuterium exchange with D₂O rate at various hercynine concentrations using EanB or EanB_Y353F2Tyr. The 1-ml reaction mixture contains 8 ~ 50 μM EanB_WT (or 0.65 ~ 6.5 μM EanB_Y353F2Tyr), 100 ~ 3000 μM hercynine, selenocystine saturated solution (1 mg powder added), 0.5 μM MetC in 50 mM KPi buffer, with pD of 8.22. The K_obsd at different hercynine concentration is calculated based on the slope from the semilogarithmic plot of the reaction conversion vs time.