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. 40 



Molecular Weight and Isoform Determination of Lobster PPO 



Figure 7 shows the SDS-PAGE (reduction condition) patterns for both 

 lobster PPO enzymes; the Florida spiny lobster PPO had three isoforms and 

 the Western Australian lobster PPO had two. The molecular masses of the 

 Florida lobster PPO subunits were determined to be 82, 88, and 97 kD, 

 while those of the Australian lobster were 87 and 92 kD. The molecular 

 masses of these subunits were higher than those of white shrimp (30 kD), 

 pink shrimp (40 kD), grass prawn (63 and 80 kD) and antarctic krill (75 

 and 83 kD) (Simpson et al . , 1987, 1988a; Ohshima and Nagayama, 1980; Rolle 

 et al., 1991), but lower than that of brown shrimp (210 kD) (Madero and 

 Finne, 1982). Multiple molecular forms with different molecular masses 

 were observed for PPO from various plant sources (Vamos-Vigyazo, 1981). 

 Mushroom PPO was reported to have 4 isoforms (isozymes), each had 

 molecular masses of 34.5 kD (Bouchilloux et al . , 1963). Apple PPO was 

 shown to have 3 isoforms with molecular masses of 24, 67, and 134 kD, 

 respectively (Demenyuk et al., 1974). PPO from banana was reported to 

 possess two isoforms with molecular masses of 12 and 60 kD, respectively 

 (Palmer, 1963). Regarding potato, multiple isoforms of PPO bearing varied 

 molecular masses have been reported by many workers (Anisimov et al.,1978; 

 Constantinides and Bedford, 1967; Patil and Evans, 1963; Thomas et al . , 

 1978). Although Florida spiny lobster and Western Australian lobster were 

 grown in different habitats, a recent study using immunological techniques 

 with rabbit antisera against the Florida spiny lobster PPO revealed that 

 these two lobsters shared cross-reactivity (Rolle et al . , 1991). 



