Studies on enzymatic properties of transglutaminase from the muscles of aquatic animals with applications to surimi-based products

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1. Transglutaminase (TGase) is an enzyme that catalyzes Ca^<2+>-dependently the formation of covalent epsilon -(gamma -glutamyl)lysine cross-links in proteins. The enzyme was identified in all muscle tissues of eleven marine animals analyzed and contained in the activity range of 2.4-0.1 unit/g. Carp enzyme is similar in catalytic properties and molecular weight (80,000 Da) to well known mammalian liver enzymes, but significantly differs from scallop enzyme, which was purified from the aductor muscle, in enzymatic properties such as km value and Ca^<2+> dependency. Reactivity of carp TGase to various fish actomyosins was investigated in terms of the velocity of polymerization of actomyosin and was different in source of actomyosin; the highest values was obtained from walleye pollack actomyosin, followed by rainbow trout, chum salmon, atka mackerel, white croaker, and carp. These results suggest that TGase-mediated cross-linking reaction of actomyosin may be mainly regulated by conform … More ational factors of the substrate actomyosin depending upon fish species.2. Suwari (setting) is a very important process with significant influence on the rheological properties of kamaboko, a traditional food in Japan. It is well known that set gel is formed depending on the amount of cross-linked myosin polymers produced during the setting. In this report we demonstrated that the cross-linked myosin polymers are enzymatically produced by TGase contained in fish muscle or surimi. The studies on effects of monovalent cations on TGase-mediated cross-linking of myosin in a set gel revealed that the set and cooked gels having strong firmness were formed by the addition of NaCl to above 0.2M with concomitant formation of cross-linked myosin polymers. On the other hand the setting of the fish paste containing KCl was not linked to the final cooked gel strength. MH_4Cl inhibited the formation of set gel. Free calcium ion, an activator of the enzyme, was found to be a critical factor to prepare the set gel when fish paste was diluted with water.Our results may be important in view of the fact that setting, a traditional manufacturing process for production of kamaboko, involves enzymatic process, and provide new insight into further improvement of the manufacturing process and developing new fabricated foods. Less