The recombinant L-asparaginase from Z. mobilis expressed extracellularly by the E. coli BL21(DE3)/pET26b/ans clone was evaluated in cytotoxicity tests on Reh cells and primary cells of patients with ALL, which indicated the potential antileukemic activity of the enzyme where cytotoxic activity was indeed detected. The gene discussed is ASPG; the disease is acute lymphoblastic leukemia.