29 

 shrimp (Madero and Finne, 1982). PPO from white shrimp {Penaeus 

 setiferus) had a pH optimum at 7.5, while that from pink shrimp {Penaeus 

 duorarum) was 8.0 (Simpson et al . , 1987, 1988a). Ohshima and Nagayama 

 (1980) showed that catecholase isolated from antarctic krill {Euphausia 

 superba) had a pH optimum at 6.5. PPO isolated from grass prawn was shown 

 to have a pH optimum at 6.0 (Rolle et al . , 1991). For plant PPO, the pH 

 optimum of 7.0 was observed for mushroom (Dawson and Mager, 1962), apple 

 (Stelzig et al . , 1972), and banana (Galeazzi and Sgarbieri, 1978), 

 respectively, while pear PPO was reported to have a pH optimum at 4.0 

 (Rivas and Whitaker, 1973). 



With respect to the pH-related relative activity, the Western 

 Australian lobster PPO had a broader pH range (from 5 to 9) than that 

 observed for the Florida spiny lobster PPO. The behavior of Florida 

 lobster PPO to various pH environments observed in this study was similar 

 to that of IPOl (inert phenoloxidase) and TAPOl (trypsin activated 

 phenoloxidase) forms from a study by Ferrer et al . (1989a). For white and 

 pink shrimp PPO, the optimal pH environments ranged from 6-7.5 and 6.5- 

 9.0, respectively (Simpson et al . , 1988a). 



Data in Table 1 indicated that crustacean (Florida spiny lobster, 

 Western Australian lobster, pink shrimp, white shrimp, brown shrimp, and 

 grass prawn) PPOs had a narrow range of optimum pH between 6 to 8. 

 However, a broad range of pH optimum between 4 and 7 was observed for 

 mushroom and other plant (potato, apple, peach, pear, and banana) PPOs. 

 Aylward and Haisman (1969) proposed that the optimum pH of PPO activity, 

 which usually ranged between pH 4 and 7, varied with enzyme sources and 

 substrates used. 



