Residual activity of mutants C457D, C457D/A525F, C457D/N211D, C457D/N211A and C457D/N211K, after preincubation at 35°C.

Residual enzymatic activity per mg of protein of mutants C457D (♦), C457D/A525F (▪), C457D/N211D (▴), C457D/N211A (▵) and C457D/N211K (•) was determined after 30, 60, 120 and 240 min of preincubation at 35°C in the absence of substrate. Dotted lines are used for the mutants at position 211. After preincubation, the homogenates were incubated with substrate for 4 h at 25°C. Values are the means of at list two separate experiments, each one carried out in duplicate.