Purification of Dickeya solani l-Asparaginase and Study of the Influence of TiO2 and ZnO Nanoparticles on Its Enzymatic Activity

Abstract

l-asparaginase catalyzes the hydrolysis of l-asparagine to l-aspartate and ammonia. In the present study, we describe the production, purification, and preliminary characterization of Dickeya solanil-asparaginase. The purification of l-asparaginase was done using ion-exchange chromatography on HiTrap Q-Sepharose Fast Flow followed by FPLC-gel filtration chromatography on Superdex 75 pg. The presence of the enzyme was confirmed by enzymatic activity measurements along with SDS-PAGE analysis. The purified l-asparaginase was shown to exhibit specificity towards l-asparagine, while being inactive against l-glutamine. This data allows us to suggest that the l-asparaginase from Dickeya solani might be clinically more relevant than, e.g., the l-asparaginase isolated from E. coli which hydrolyzed also l-glutamine and produces l-glutamate, a neurotoxic agent. We also demonstrated that the enzymatic activity was enhanced in the presence of TiO2 and ZnO nanoparticles, making them good candidates to improve l-asparaginase activity. Indeed, the results obtained show that the TiO2 nanoparticles increased the activity of l-asparaginase by a factor of 6.0 while the ZnO nanoparticles increased it twice.