Properties of Arginase from the Hepatopancreas of Giant Freshwater Prawn ( Macrobrachium rosenbergii , de Man).

We describe the hepatopancreas arginase activity of freshwater prawn ( Macrobrachium rosenbergii). The enzyme was isolated using reactive blue 2- agarose affinity chromatography and gel filtration on Sephadex G-150. The enzyme had a specific activity of 5.70 μmol/min/mg of protein. The enzyme exhibited a maximal activity at pH 8.5 and Km of 12.5 mM. The enzyme was capable of hydrolysing L-arginine and to a lesser extent, L-arginine monohydrochlorate and L-arginine monohydrate. The optimum temperature of the enzyme was 35 0C. The molecular weight as determined by gel filtration was approximately 160,000 dalton and SDS-PAGE, was 22,000 dalton. The different amino acids (L-lysine, L-cysteine, Lvaline, L-proline, L-aspartic acid, L-glutamic acid and L-serine) and metal ions (Ni 2+ , Co 2+ , Zn 2+ , Mn 2+ and Mg 2+ ) did not show any inhibition on the enzyme activity. The enzyme was activated with Mn 2+ and different concentration of Mn 2+ had no effect on the enzyme activity. EDTA, citrate and urea showed considerable inhibition on the enzyme activity. Key words: Freshwater prawn; arginase; uricotelism; invertebrates; hepatopancreas