Figure 4.

Global fitting of spinach E3 progress curves, NAD⁺ activation, and pH-dependent data obtained from Matthews and Reed (13) (see Supporting Material For data). All data (symbols) were fitted to two models in which the K_d for substrates and products was either independent (solid lines) or dependent (dashed lines) of the enzyme redox state, as described in Methods. (A) Progress-curve data for the reverse reaction in different NAD⁺ concentrations (pH 6.3), with data obtained from Fig. 4 in Matthews and Reed (13). (B) Progress-curve data for the forward reaction with varied pH, with data obtained from Fig. 7 of Matthews and Reed (13). (C) Initial velocity of the reverse reaction as a function of pH and NAD⁺ concentration, with data obtained from Fig. 6 of Matthews and Reed (13). (D) Activation of reverse initial velocity with increasing NAD⁺ concentration (pH 6.3), with data obtained from Fig. 5 of Matthews and Reed (13). To see this figure in color, go online.