Phenoloxidase from the Cuticle of Florida Spiny Lobster ( Panulirus argus ): Mode of Activation and Characterization

Phenoloxidase (PO) from lobster cuticle existed as a large inert enzyme (IPO1) which became active (15‐fold increase) upon incubation at 4°C and 3 days storage. Electrophorcsis of day 3 extracts showed that the large enzyme disappeared gradually while a new PO (EAPO) developed (Mw of 62.5 kDA). Trypsin treatment yielded a similar enzyme (TAPO2; 64 kDA). Kinetic properties such as Km and E a indicated that dihydroxyphenylalanine (DOPA) appeared to be a more physiologically important substrate for the trypsin treated PO than EAPO. In addition, temperature and pH properties indicated that different structural and functional properties existed between the three forms (IPO1, EAPO, TAPO2).