CHARACTERIZATION AND COMPARISON OF CRUSTACEAN AND PLANT POLYPHENOL 

 OXIDASES: KINETICS AND SOME PROPERTIES 



Introduction 



Polyphenol oxidase (PPO) (E.C. 1.14.18.1.), also known as 

 tyrosinase, polyphenol ase, phenolase, catechol oxidase, cresolase, and 

 catecholase, is widely distributed in nature (Schwimmer, 1981). In 

 addition to its general occurrence in plants, it can also be found in 

 microorganisms, especially in fungi, and in some animal organs (Brown, 

 1967). Unfavorable darkening of many fruits and vegetables after cutting 

 is primarily due to the action of this enzyme. Enzymatic browning of 

 fruits and vegetables due to PPO activity has been widely reported 

 (Flurkey and Jen, 1978; Harel et al . , 1966; Macrae and Duggleby, 1968; 

 Mapson et al . , 1963; Mosel and Herrman, 1974; Palmer, 1963; Patil and 

 Zucker, 1965; Sciancalepore and Longone, 1984; Walker, 1962, 1964; Weurman 

 and Swain, 1955). However, the role of PPO in crustaceans is not well 

 documented considering the variation in susceptibility to melanosis. 



PPO plays an important role in the sclerotization of insects and 

 crustaceans during the molting cycle (Andersen, 1971; Brunet, 1980; 

 Summers, 1967; Vinayakam and Nellaiappan, 1987). However, it is the 

 formation of melanins causing darkening on the surface of seafood products 

 due to PPO action which is of concern to the seafood industry. PPO 

 enzymes from various crustaceans have been partially characterized (Madero 

 and Finne, 1982; Nakagawa and Nagayama, 1981; Simpson et al., 1987, 



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