R. Asokan et al., ACTIVATION OF PROPHENOLOXIDASE IN THE PLASMA AND HEMOCYTES OF THE MARINE MUSSEL - PERNA VIRIDIS LINNAEUS, Developmental and comparative immunology, 21(1), 1997, pp. 1-12
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.