Two substrate kinetics for sporidesmin and glutathione with GRx1. Concentrations of GSH and sporidesmin were varied in the presence and absence of GRx1. The two substrate kinetic analysis of sporidesmin (7.6–76 μM) and GSH (0.4 mM, solid square), (2 mM, solid diamond), (5 mM, solid triangle) with GRx1 (0.035 μM) shows an intersecting pattern of lines consistent with a sequential mechanism. Each point represents the mean value, plus and minus the standard error, for at least three determinations. Where error bars are not evident they are within the size of the symbol.