Fig. 2: Tyr110 of ScGrx7 is part of the glutathione-scaffold site in the GSSCys assay.

a, b Selected \(k_{{\mathrm{cat}}}^{{\mathrm{app}}}\) and \(K_{\mathrm{m}}^{{\mathrm{app}}}\) values of ScGrx7 wild-type enzyme and Y110F/H/A mutants for GSSCys and GSH. c Calculated catalytic efficiencies from panels (a) and (b). d Reciprocal Dalziel coefficients, which probably reflect the second order rate constants of the oxidative and reductive half-reaction with GSSCys and GSH, respectively. e Summary of the altered kinetic parameters for Y110F/H/A. f Reaction sequence for the GSSCys assay in accordance with the observed ping-pong kinetics. Please note that the \(K_{\mathrm{m}}^{{\mathrm{app}}}\) values are not solely defined by the ratios k₋₁/k₁ and k₋₄/k₄ but are also affected by other rate constants. Hence, the \(K_{\mathrm{m}}^{{\mathrm{app}}}\) values do not reflect true substrate affinities as shown previously¹². Source data are provided in the Supplementary Information: original plots and kinetic parameters for panels a–c are shown in Supplementary Fig. 2 and Supplementary Table 2. Statistical analyses and P values for the \(k_{{\mathrm{cat}}}^{{\mathrm{app}}}\) and \(K_{\mathrm{m}}^{{\mathrm{app}}}\) values from panels a and b are listed in Supplementary Table 11. Error bars are the calculated standard error from the curve fits in SigmaPlot 13. Reciprocal Dalziel coefficients for panel d were obtained from Supplementary Fig. 3 and are listed together with the true k_cat values in Supplementary Table 1.