L-asparaginase from bacterial sources have been used in antineoplastic treatments and the food industry. A novel type II L-a sparaginase encoded by the N-truncated gene ansZP21 of halotolerant Bacillus subtilis CH11 isolated from Chilca salterns in Peru was expressed using a heterologous system in Escherichia coli BL21 (DE3)pLysS. The recombinant protein was purified using one-step nickel affinity chromatography and exhibited activity of 234.38 U mg-1 and a maximum catalytic activity at pH 9.0 and 60 °C. The enzyme shows a homotetrameric form with an estimated molecular weight of 155 kDa by gel filtration chromatography. The enzyme half-life at 60 °C was 3 h 48 min, and L-asparaginase retained 50% of initial activity for 24 h at 37 °C. The activity was considerably enhanced by KCl, CaCl2, MgCl2, mercaptoethanol, and DL-dithiothreitol (p-value < 0.01). Moreover, the Vmax and Km were 145.2 µmol mL-1 min-1 and 4.752 mM, respectively. These findings evidence a promising novel type II L-asparaginase for future industrial applications.

Acute lymphoblastic leukaemia is currently treated with bacterial L-Asparaginase; however, its side effects bring up the special need for improved and efficient novel enzymes development. Previously, we obtained low anti-asparaginase antibody production and high serum enzyme half-life in mice with the P40S/S206C mutant; however, its specific activity was significantly reduced. Thus, our aim was to test single mutants, S206C and P40S, for in vitro and in vivo assays. Our results showed that the drop in specific activity was caused by P40S substitution. Besides, our single mutants were highly stable in biological environment simulation, unlike double mutant P40S/S206C. The in vitro cell viability assay demonstrated that mutant enzymes have higher cytotoxic effect than WT on T-cells derived ALL and on some solid cancer cell lines. The in vivo assays were performed in mice to identify toxicological effects, to evoke immunological response and to study the enzymes pharmacokinetics. From these tests, none of the enzymes was toxic; however, S206C evoked lower physiological changes and immune responses. In relation to pharmacokinetic profile, S206C has two-fold higher activity than WT and P40S two hours after injection. In conclusion, we present bioengineered E. coli asparaginases with high specific enzyme activity and lesser side effects.