Molecular Cloning, Biochemical Characterization, and Antitumor Properties of a Novel L-Asparaginase from Synechococcus elongatus PCC6803.

L-asparaginase (EC 3.5.1.1), which catalyzes the deamidation of L-asparagine to L-aspartic acid and ammonia, has been widely used as a key therapeutic tool in the treatment of tumors. The current commercially available L-asparaginases, produced from bacteria, have signs of toxicity and hypersensitivity reactions during the course of tumor therapy. Therefore, searching for L-asparaginases with unique biochemical properties and fewer adverse effects was the objective of this work. In this study, cyanobacterial strain Synechococcus elongatus PCC6803 was found as a novel source of L-asparaginase. The L-asparaginase gene coding sequence (gi:939195038) was cloned and expressed in E. coli BL21(DE3), and the recombinant protein (Se.ASPII) was purified by affinity chromatography. The enzyme has high affinity towards L-asparagine and shows very weak affinity towards L-glutamine. The enzymatic properties of the recombinant enzyme were investigated, and the kinetic parameters (Km, Vmax) were measured. The pH and temperature dependence profiles of the novel enzyme were analyzed. The work was extended to measure the antitumor properties of the novel enzyme against different human tumor cell lines.