Fig. 1

Characterization of PO activity in the hemolymph of B. glabrata (n = 15) and B. alexandrina (n = 15). PO activity in the hemolymph of both species of snails were assessed with three PO substrates: L-tyrosine (metabolized by tyrosinase only), L-DOPA (metabolized by catecholase, laccase and tyrosinase) and p-phenylenediamine (PPD) (metabolized by laccase only). No PO activity was detected with L-tyrosine whereas strong activity was measured with PPD, demonstrating the presence of laccase activity in the hemolymph. Significant inhibition of the activity with diethylthiocarbamate (DETC), a specific inhibitor of PO enzymes, demonstrates the specificity of the activity measured. Comparisons between substrates were done using absorbance values obtained 4 h after adding the substrates at 10 mM, before reaching the plateau phase of the PO activity