Activation of phenoloxidase activity by humoral lectin in hemocytes of freshwater crab Paratelphusa jacquemontii

The lectin, Pjlec isolated from the hemolymph of the freshwater crab Paratelphusa jacquemontii hemagglutinated (HA) with mice, rabbit and rat erythrocytes. However, the lectin failed to agglutinate neraminidase treated asialylated erythrocytes showing its sialic acid specificity. The poyacyrlamide gel electrophoresis of lectin yielded 310 kDa proteins, on sodium sulphate dodecyl (SDS) gel appeared as a tetramer with subunits of 76 kDa. The observation of in vitro phagocytosis in granular hemocytes of lectin opsonized rabbit erythrocyte by Transmission electron microscopy (TEM) showed the release of lytic vesicles by exocytosis prior to engulfment. The Pjlec lectin also showed an ability to oxidize L-3, 4 dihydroxyphenylalanine (L-DOPA) and in hemocyte lysate preparation (HLS) was enhanced on reduction with SDS and on proteolytic cleavage with trypsin. The lectin appeared to have a regulatory role in activation of enzyme activity associated with phagocytosis and melanin formation.