Purification and characterization of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428

An intracellular glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428 was isolated to apparent homogeneity. The homotetramer enzyme has a molecular mass of 144.4 kDa (MALDI-TOF MS) and an isoelectric point of approximately 8.4. The enzyme is very specific for its natural substrate, L-asparagine. The activity of L-asparaginase is activated by mono cations and various effectors including Na+, K+, L-cystine, L-histidine, glutathione and 2-mercaptoethanol whereas it is moderately inhibited by various divalent cations and thiol group blocking reagents. Kinetic parameters, K-m, V-max and k(cat) of purified L-asparaginase from P. carotovorum MTCC 1428 were found to be 0.657 mM, 4.45 U mu g(-1) and 2.751 x 10(3) s(-1), respectively. Optimum pH of purified L-asparaginase for the hydrolysis of L-asparagine was in the range of 8.0-10.0, and its optimum temperature was found to be 40 degrees C. The purified L-asparaginase has no partial glutaminase activity, which can reduce the possibility of side effects during the course of anti-cancer therapy. (C) 2010 Elsevier Ltd. All rights reserved.