Activation of brain IMPA1 by S100B under different experimental conditions. Purified bovine brain S100B and IMPA1 were used in the activity assays. Non-specific IMPA1 activity was measured in the presence of high concentrations of LiCl (60 mM). a Activity in the presence and absence of S100B; b activity in the presence of various concentrations of S100B; c substrate-dependent activity in the presence and absence of S100B; d calcium-dependent and -independent activity in the presence and absence of S100B. Note in d, IMPA1 activity is significantly inhibited in the presence of high calcium. The data presented in a, c, and d are the mean±SE of three independent experiments (n=3) performed in duplicates. Statistical significance was calculated using GraphPad Prism, unpaired Student’s t test for independent samples, version 4.0 (GraphPad Software). A value of P<0.05 was accepted as statistically significant