Abstract:
Phenoloxidase activity in crayfish haemocyte lysates and extracts of haemocyte
membranes were studied using native PAGE and SDS-PAGE gels and
staining for cresolase, catecholase and laccase activities. The activation of the
proenzyme, prophenoloxidase to phenoloxidase, in native PAGE was demonstrated
following exposure to SDS. By staining samples separated in SDSPAGE
followed by renaturation, a high molecular mass phenoloxidase
activity was identified in both the soluble and membrane fractions of haemocyte
preparations. The membrane-associated activity appeared at only relatively
high molecular mass (>300 kDa), and could easily be eluted from
membranes using detergents or NaCl. Further, this membrane-associated
activity has a catecholase activity but not the cresolase activity seen in the
soluble preparations. In addition, several other phenoloxidase enzymes were
identified with di#erent relative mobilities (250, 80, 72 and 10 kDa). Crayfish
haemocytes also contained laccase activity, thought to be restricted to cuticle
sclerotisation in the integument. Laccase activity in haemocytes might aid in
the formation of capsule used to contain pathogens.
