Fig. 1.

Thermal inactivation for the activities of the wild-type (•), S213C (□), I33L (▪), and I33L S213C (○) variant enzymes of d-psicose 3-epimerase from A. tumefaciens at 50°C (A) and 55°C (B). A sample was withdrawn at each time interval, and the relative activity was determined under identical conditions in 50 mM EPPS buffer (pH 8.0) containing 20 mM fructose and 0.21 U/ml of enzyme at 50°C for 10 min. Data represent the means of three experiments, and error bars represent standard deviations.