Fig. 7.

Kinetics of uncatalyzed elimination of H₂O₂ by reduced glutathione._. a Traces of time-dependent changes to the excitation ratio (R^488/405) of recombinant HyPer introduced into a solution of H₂O₂ (10 μM) that had been preincubated with GSH (3 mM) for increasing time periods, as indicated. Note the inverse relationship between HyPers oxidation rate and the length of the preceding H₂O₂-GSH preincubation. b As in a but following HyPer introduction into premixed solutions of H₂O₂ (10 μM) and reduced glutathione (GSH) at the indicated concentrations (0–3 mM). c As in a, but HyPer was exposed sequentially to H₂O₂ (2 μM) and various concentrations of GSH. d A plot of HyPer oxidation rate (reflecting the residual [H₂O₂]) as a function of GSH concentration. The slope (–0.0036 s^–1 mM^–1) and the y-intercept (0.01263 s^–1) of the curve were used to extract the dependence of H₂O₂ consumption rate (–d[H₂O₂]/dt, at 10 μM H₂O₂) on each GSH concentration point (0–3 mM) according to Eqs. (2)–(4). The bimolecular rate constant was calculated by division of the slope of the resulting curve (shown in the inset) by the initial [H₂O₂] (10 μM)