Purification and characterization of arginase from eggs of the Tick Hyalomma dromedarii

ABSTRACT

Two arginases, A and B, from developing embryos of the tick Hyalomma dromedarii were purified about 20.50 and 52.29 fold, respectively. The molecular weight of arginase B, as determined by gel filtration on Sephadex G-100, was about 120.266 +/- 2250. The two enzymes were capable to hydrolyze L-arginine and to some extent L-canavanina at arginase canavanase ratio [> 10]. The enzymes A and B were found to be stable up to 70C, while a loss of 53.84 and 62.50% was recorded at 80C, respectively. Both enzymes exhibited a maximal activity at pH 9.5. The Km values were 3.70, 2.50 mM for arginase A and 5.00, 1.88 mM for arginase B at pH 7.5 and 9.5, respectively. Arginases A and B require Mn+2 for maximal activity, losing 58.7 and 84.7% of activity by dialysis against 50 mM EDTA-buffer for 2 hours. 79% of arginase B activity was recovered by treatment with 50 mM mM+2 buffer for 2 hours. Inhibition of arginases A and B other divalent cations, proline and branched-chain amino acids was studied. L-ornithine and L-lysine caused a mixed-type inhibition for the two arginases