Purification and Characterization of Arginine Deiminase from E. coli and Its Differentially Cytotoxic Effect on Normal and Cancer Cell Lines

Abstract

   In this study, the author is concerned with the purification, extraction and biochemical analysis of arginine deiminase (ADI) of a clinical strain of Escherichia coli to determine its anticancer properties. Ammonium sulfate precipitation followed by two subsequent purification processes such as Ion-exchange chromatography and gel filtration enhanced the purity 9.5 fold and the final specific activity was found to be 16 U/ mg with the molecular weight of 46 kDa . The enzyme was observed to be most active at pH 7.0 and 37^oC and lost less than 75% of its trial activities at marginally acidic to neutral pH. Using metal ion analysis and the fact that ADI was a metalloenzyme; Fe ³⁺ and Mn ²⁺ were found to increase the ADI activity, whereas EDTA suppressed the activity significantly. In vitro cytotoxic testing by MTT technique showed that ADI dose dependently and specifically suppressed the viability of HeLa cancer cells with the IC₅₀ of 140.55 ug/mL, whereas the normal HEK293 cells had the IC₅₀ of 253.47 ug/mL, with a selectivity index of 1.80. This justifies the therapeutic potential of bacterial ADI as a specific anticancer agent of arginine-auxotrophic tumors.