Purification, Characterization and Comparison between Two New L-asparaginases from Bacillus PG03 and Bacillus PG04

BACKGROUND: L-asparaginase has been used as a chemotherapeutic agent in treatment of lymphoblastic leukemia. In the present investigation, Bacillus sp. PG03 and Bacillus sp. PG04 were studied. METHODS: L- asparaginases were produced using different culture media and were purified using ion exchange chromatography. RESULTS: Maximum productivity was obtained when asparagine was used as the nitrogen source at pH 7 and 48 h after cultivation. New intracellular L-asparaginases showed an apparent molecular weight of 25 kDa and 30 kDa by SDS-PAGE respectively. These enzymes were active in a wide pH range (3-9) with maximum activity at pH 6 for Bacillus PG03 and pH 7 for Bacillus PG04 L-asparaginase. Bacillus PG03 enzyme was optimally active at 37 ˚C and Bacillus PG04 maximum activity was observed at 40˚C. Kinetic parameters k(m) and V(max) of both enzymes were studied using L-asparagine as the substrate. Thermal inactivation studies of Bacillus PG03 and Bacillus PG04 L-asparaginase exhibited t(1/2) of 69.3 min and 34.6 min in 37 ˚C respectively. Also T(50) and ∆G of inactivation were measured for both enzymes. CONCLUSION: The results revealed that both enzymes had appropriate characteristics and thus could be a potential candidate for medical applications.