Characterization of phenoloxidase of Penaeus indicus

The enzyme phenoloxidase from haemolymph of Penaeus indicus was partially purified us- ing ammonium sulphate fractionation technique. An overall recovery of 52% with a 5-fold purification was achieved. Dialysis reduced the enzyme activity indicating the presence of dialysable cofactors. The enzyme had high afinity for the biphenolic substrate adrenalin fol- lowed by dopamine, catechol and dopa. The rate of the reaction was linear up to 3 min when adrenalin was used as the substrate. The enzyme had an optimum tem erature of 50°C but lost 60% of its activity when heated to 70°C for 10 min. The Krn and t"max of the enzyme with adrenalin as the substrate was 0.122 mM and 0.588 OD unitslmg protein a min respectively. The enzyme was inhibited by the substrate adrenalin at a concentration of IS mM and by cupric salts. Magnesium and calcium stimulated the enzyme activity. EDTA and mercaptoethanol strongly inhibited the enzyme