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 (Ni2+, Co2+, Zn2+, Mn2+ and Mg2+) did not show any inhibition on the enzyme activity. The enzyme was activated with Mn2+ and different concentration of Mn2+ 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; hepatopancrea