Insight into the Mechanistic Basis of the Hysteretic-Like Kinetic Behavior of Thioredoxin-Glutathione Reductase (TGR)

Figure 4

Dependence of initial velocities of T. crassiceps TGR on either GSSG (a) or NADPH (b) concentrations. Data were obtained as described under Materials and Methods. (a) GSSG as the variable substrate at the following constant concentrations of NADPH: (▲) 3 μM; (○) 8 μM; (●) 40 μM. (b) NADPH as the variable substrate at the following constant concentrations of GSSG: (▲) 4 μM; (○) 10 μM; (●) 35 μM. In all the enzyme assays, the final concentration of enzyme subunit was 14 nM. In order to avoid overlapping of data, only results obtained at three constant concentrations of the corresponding fixed substrate is shown. Continuous lines were obtained from equation (5) using the parameters resulting from the global adjustment of data. Each point represents mean ± standard deviation (n=6).

(a)

(b)