L-ASN activity and cell-kill assays. All experiments were conducted 3 times (n = 3). SDs were calculated for each protein. (A) Asparaginase activity measured for WT and mutant L-ASN. (B) Glutaminase activity for WT and mutant L-ASN. IC50 values were estimated for WT and mutants at asparaginase-equivalent doses of the compounds, thus reflecting the sole impact of modification of glutaminase activity on drug cytotoxicity. (C) Cytotoxicity assays on drug-sensitive SupB15 cells. (D) Cytotoxicity assays on intermediate drug-sensitive MV4:11 cells. (E) Cytotoxicity assays on drug-resistant REH cells. *P < .05; **P < .01.