Abstract

L-Asparaginase (EC 3.5.1.1) is produced from actinomycetes to avoid the hypersensitive effect of that produced from other bacteria. Streptomyces halstedii strain was isolated from Egyptian soil and produced L-asparaginase. The 55.2-fold purified enzyme obtained had a final specific activity of 2071.2 U/mg. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed one band with molecular weight of 100 KDa. The K_m value was 0.1939 mM. The enzyme showed maximum activity at pH 8.0, at optimum temperature at 37°C. Ethylene diamine tetraacetic acid (EDTA) and metal ions such as Zn²⁺, Hg²⁺ Cu²⁺ and K⁺ decreased the activity of the enzyme. Ions such as Ca²⁺ and Fe²⁺ did not affect the activity of the enzyme. The enzyme showed cytotoxic activity against Ehrlich ascites cells (EAC) in vitro. In vivo, it showed a significant reduction in malondialdehyde (MDA) levels as the end product of lipid peroxidation and a remarkable increase in activity of liver antioxidant enzymes, [superoxide dismutase (SOD), catalase (CAT)] and a reduction in tumor weight. In conclusion, L-asparaginase from S. halstedii showed anti-tumor activity and cytotoxic effect against cancer cell line in vitro and in vitro. The reduction of tumor size in albino mice may be attributed to the elevation of CAT and SOD activities as well as the diminishing of MDA. 

Key words: L-Asparaginase purification, antitumour activity, Streptomyces sp.