Cresolase, catecholase and laccase activities in haemocytes of the red swamp crayfish

Phenoloxidase activity in crayfish haemocyte lysates and extracts of haemoc yte membranes were studied using native PAGE and SDS-PAGE gels and staining for cresolase, catecholase and laccase activities. The activation of the p roenzyme, prophenoloxidase to phenoloxidase, in native PAGE was demonstrate d following exposure to SDS. By staining samples separated in SDS-PAGE foll owed by renaturation, a high molecular mass phenoloxidase activity was iden tified in both the soluble and membrane fractions of haemocyte preparations . The membrane-associated activity appeared at only relatively high molecul ar mass (>300 kDa), and could easily be eluted from membranes using deterge nts or NaCl. Further, this membrane-associated activity has a catecholase a ctivity but not the cresolase activity seen in the soluble preparations. In addition, several other phenoloxidase enzymes were identified with differe nt relative mobilities (250, 80, 72 and 10 kDa). Crayfish haemocytes also c ontained laccase activity, thought to be restricted to cuticle sclerotisati on in the integument. Laccase activity in haemocytes might aid in the forma tion of capsule used to contain pathogens. (C) 2000 Academic Press.