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Purpose: L-asparaginase has been widely recognized as a critical component in the treatment of various types of lymphoproliferative disorders, since its introduction in 1960s. However, its use in some cases leads to allergic reactions rendering the continuation of treatment unfeasible. Thus, the development of L-asparaginase from alternative sources or the production of engineered enzymes have always been considered. This study aimed to produce and evaluate a novel enzyme designed based on the sequence of L-asparaginase from Escherichia coli bacteria with Y176F/S241C mutations. Methods: The Y176F/S241C mutant L-asparaginase was successfully expressed as the GST-fusion protein in E. coli , and then was subjected to affinity and size exclusion chromatography. The activity of the purified enzyme was determined based on the released ammonia as the result of substrate hydrolysis using Nessler's reagent. Chemical denaturation experiment in the presence of increasing concentration of guanidinium chloride was applied to determine the folding stability of the purified enzyme. Results: The mutant enzyme was purified with an efficiency of 77-fold but at a low recovery of 0.7%. The determined kinetic parameters Km, Vmax, kcat, specific activity and catalytic efficiency were 13.96 (mM), 2.218 (mM/min), 273.9 (min-1), 237.8 (IU/mg) and 19.62 (mM-1 min-1), respectively. Moreover, unfolding free energy determined by guanidinium chloride induced denaturation for mutated and commercial L-asparaginase enzymes were 8421 J/mol and 5274 J/mol, respectively. Conclusion: The mutant enzyme showed improved stability over the wild-type. Although the expression level and recovery were low, the mutant L-asparaginase demonstrated promising activity and stability, with potential clinical and industrial applications. [ABSTRACT FROM AUTHOR]

Purpose: Medical usage of L-asparaginase (ASNase), the first-line of acute lymphoblastic leukemia treatment, is linked to allergic responses and toxicities, which necessitates the development of new bio-better ASNases. The aim of the current study was in silico design of a novel ASNase with predicted improved enzymatic properties using strategies encompassing sequence-function analysis of known ASNase mutants. Additionally, current study aimed to show that the new enzyme is active. Methods: Based on 21 experimentally reported mutations for ASNase, a virtual library of mutated enzymes with all 7546 possible combinations of up to 4 mutations was generated. Three-dimensional models of proposed mutant enzymes were built and their in silico stabilities were calculated. The most promising mutant was selected for preparing a genetic construct suitable for expression of the designed ASNase in bacterial cells. Results: Computational study predicted that Y176F/S241C double mutation of Escherichia coli ASNase may increase its folding stability. The designed ASNase was expressed in two different E. coli strains (Origami B(DE3) and BL21(DE3)pLysS) and then the soluble fractions prepared from the cell lysates of the host cells were used in enzyme activity assay. Results showed that enzyme activity of soluble fraction from Origami (95.4 ± 7.5 IU/0.1 mL) was four times higher than that of soluble fraction from pLysS (25.8 ± 2.5 IU/0.1 mL). Conclusion: A novel functional double mutant ASNase with predicted improved enzymatic properties was designed and produced in E. coli. The results of the current study suggest a great commercial potential for the identified enzyme in pharmaceutical and industrial applications. [ABSTRACT FROM AUTHOR]