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

Figure 1

Initial velocity patterns of T. crassiceps TGR. Enzyme assays were carried out as described under Materials and Methods at 25°C and pH 7.8 in the presence of low concentrations of GSSG. (a) GSSG as the variable substrate at the following fixed concentrations of NADPH: (●) 1.5 μM; (Δ) 3μM; (■) 5.5 μM; (○) 15 μM. (b) NADPH as the variable substrate at the following fixed concentrations of GSSG: (●) 3.1 μM. (○) 6.2 μM; (▼) 12 μM; (□) 36 μM. The final enzyme subunit concentration was 6.1 nM. Continuous lines were obtained from the corresponding double-reciprocal form of equation (1) using the parameters resultant from the global fitting of data (each point represents mean ± standard deviation (n=6).

(a)

(b)