ACTIVATION OF PROPHENOLOXIDASE IN THE PLASMA AND HEMOCYTES OF THE MARINE MUSSEL - PERNA VIRIDIS LINNAEUS

Phenoloxidase activity was detected in plasma and haemocytes of the ma rine mussel Perna viridis. This enzyme exists as a proenzyme, propheno loxidase (proPO), in both these haemolymph fractions and could be acti vated in vitro by exogenous proteases (trypsin and alpha-chymotrypsin) and a detergent (sodium dodecyl sulphate). In addition, laminarin (a polymer of beta-1,3 glucan) and bacterial lipopolysaccharides (LPSs) e ffectively triggered proPO activation in these haemolymph fractions. T he activation of proPO by non-self molecules was dependent upon calciu m ions at a low concentration. This activation process appeared to inv olve a limited proteolysis, since serine protease inhibitors (soybean trypsin inhibitor, benzamidine or p-nitrophenyl-p'-guanidinobenzoate) suppressed conversion of proPO to the active enzyme. This study demons trates the selective response of plasma and haemocytic proPO to activa tion by different types of bacterial LPS tested and suggests that proP O system in both plasma and haemocytes of P. viridis serves an importa nt function in non-self recognition and host immune reactions. (C) 199 7 Elsevier Science Ltd.