The Phenoloxidase Activity in Prawn Hemocytes

Abstract

Studies were made on the distribution of phenoloxidase (PO) activity in the blood of kuruma prawn, Penaeus japonicus. PO activity was higher in the sonicated hemocytes than in the plasma. The optimum temperature for the PO activity was 40°C. EDTA lowered the relative activity of PO to 50%, and higher temperature than 60°C or HEPES of higher molarities than 0.5 M completely inhibited the PO activity. Phenylmethylsulfonyl fluoride (5 mM) or diethyldithiocarbamate (5 mM) markedly inhibited the PO activity, suggesting that the serine protease and copper enzyme are involved in the enzyme cascade of prophenoloxidase-activating system.