Phenoloxidase activity of hemocytes derived from Penaeus monodon and Macrobrachium rosenbergii.

The phenoloxidase (PO) activity of hemocyte lysate supernatant (HLS) from both tiger shrimp (Penaeus monodon) and giant freshwater prawn (Macro-branchium rosenbergii) was examined by treating HLS with various factors, such as an increase in temperatures from 25 to 70 degrees C, one of four elicitors (beta-1,3-1,6-glucan, zymosan, heat-killed Vibrio cells, and lipopolysaccharide), trypsin, one of three protease inhibitors (soybean trypsin inhibitor, p-nitrophenyl-p'-guanidinobenzoate, and benzamidine), and one of two divalent cations (Mg2+ and Ca2+). The strongest PO activity in both animals was induced at 37 degrees C, while enzyme activity varied according to the concentration of the elicitors or cations added to the HLS samples. The following optimum concentrations were recorded: lipopolysaccharides at 0.5 mg/ml, both beta-glucan and zymosan at 1 mg/ml, and Vibrio cells at 10(6) cells/ml. In addition, for giant freshwater prawn, PO activity increased when HLS was treated with trypsin and decreased when it was separately treated with three protease inhibitors. However, effects of either trypsin or protease inhibitors did not occur in tiger shrimp. Strongest PO activity occurred in HLS treated with 20 mM of either calcium ion or magnesium ion, and the addition of the two cations led to an increase in enzyme activity; a decrease was noted following the treatment with EDTA. Cytochemical analysis revealed that prophenoloxidase system exists in the granulocytes of both tiger shrimp and giant freshwater prawn.