Study of prophenoloxidase activating system of freshwater crayfish (Pontastacus leptodactylus)

Phenoloxidase (po) activity was measusred spectrophotometrically inserum, plasma and haemocytes (hls) of the freshwater crayfish (pontastacusleptodactylus). the highest activity was found in hls suggesting that thehaemocytes are the major source of the po or its proform prophenoloxidase(propo) in crayfish. furthermore, the enzyme activity in serum samples wasreduced after freezing the samples for 20 days at -20'c. po activity was cationdependentand the neak of enzyme activity obtained using 5mm of caclz ormgf.l, also, the po activity in the hls samples treated with different elicitors of10% sodium dodecyl sulphate (lo%sds), b 1-3-glucan, aeromonas hydrophilafipopolysaccharids (lps) and trypsin resulted in variable activities with the highestand the lowest activities measured in samples treated with trypsin and 10% sds,respectively. the marked enhancement induced by trypsin suggest the role of anendogenous proteinase which is probably able to promote the enzyme activity. toconfirm the role of the proteinase on the propo activating system, trypsin activitywas also measured in the crayfish hls