Cloning, expression, and characterization of a novel thermo-acidophilic l-asparaginase of Pseudomonas aeruginosa CSPS4.

ABSTRACT

In the present investigation, a soil isolate Pseudomonas aeruginosa CSPS4 was used for retrieving the l-asparaginase encoding gene (Asn_PA) of size 1089 bp. The gene was successfully cloned into the pET28a (+) vector and expressed into E. coli BL21(DE3) for characterization of the protein. The recombinant rAsn_PA enzyme was purified by affinity chromatography using Ni-NTA2+ resins. Molecular weight analysis using SDS-PAGE unveiled rAsn_PA as a monomeric protein of molecular weight ~ 35 kDa. On characterization, the recombinant rAsn_PA showed optimum pH and temperature of 6.0 and 60 °C, respectively, along with significant stability at 50-70 °C, along with 50% residual activity at 80 °C after 3 h of incubation. Similarly, the rAsn_PA exhibited asparaginase activity over a broad pH range between 4 and 8. The enzyme was not significantly inhibited in the presence of detergents. The rAsn_PA was grouped into the asparaginase-glutaminase family II due to the glutaminase activity. The purified rAsn_PA showed antitumor activity by exhibiting a cytotoxic effect on three different cell lines, where IC50 of purified rAsn_PA was 2.3 IU, 3.7 IU, and 20.5 IU for HL-60, MOLM-13, and K-562 cell lines, respectively. Thus, recombinant rAsn_PA of P. aeruginosa CSPS4 may also be explored as an antitumor agent after reducing or minimizing the glutaminase activity. Thermo-acidophilic properties of rAsn_PA make it a novel enzyme that needs to be further investigated.