L-GLUTAMINASE produced by Streptomyces canarius FR …….(KC460654) was purified to homogeneity with an apparent molecular mass of 44 kDa. The purified enzyme was 17.9 fold with a final specific activity 132.2 U/mg protein and 28% yield recovery. The purified L- glutaminase showed a maximal activity against L-glutamine when incubated at pH 8.0 and 40°C for 30 min. The enzyme maintained its stability at wide pH range for 5.0- 11.0 and is thermally stable up to 60°C with Tm value 57.5°C. The enzyme had high affinity and catalytic activity for L- glutamine (Km 2.4 mM, Vmax 28.1 U/mg/min), followed by L- asparagine and L-aspartic acid. In vivo, the purified enzyme showed no obvious changes in liver and kidney functions. Also, it has a normal effect in all hematological parameters except slight effect on RBCs and levels of platelets as shown after 10 days of rabbit's injection with purified enzyme. Interestingly, it showed slight effect on the tested renal and liver tissues comparing with negative control. The anticancer activity of the purified enzyme was determined against five types of human cancer cell lines using MTT assay in vitro. The tested enzyme had a high efficiency against Hep-G2 cell (IC50, 6.8 μg/ml) and HeLa cells (IC50, 8.3 μg/ml), while the growth of MCF-7 cells was not affected. On the other hand, the tested enzyme had a moderate cytotoxic effect against HCT-116 cell (IC50, 64.7 μg/ml) and RAW 264.7 cell (IC50, 59.3 μg/ml).