The Relative Thermo-stabilities of the Actomyosin-ATPase from the Dorsal Muscles of Various Fish Species

Abstract

Actomyosins from the dorsal muscles of various fish species were prepared and the thermo-stability of the respective Ca2+-ATPase activities was studied. 1) The rate of inactivation of ATPase at 35° varied greatly among actomyosins from different fish species. 2) Since the inactivation of actomyosin ATPase at 25, 30, 35 and 40°C respectively, was a first order process, the rate constants of inactivation at the respective temperatures were calculated. 3) The rates of inactivation of actomyosin ATPase on incubation for definite periods were measured with respect to temperature. The temperature at which approximately fifty percent loss of ATPase activity occurred within 30 minutes varied greatly among actomyosins from various fish species. 4) From the results of the thermal inactivation studies, an order of relative thermo-stability is clearly evident, tilapia actomyosin being the most stable and eel, carp (=herabuna), yellowtail, rainbow trout (=kokanee salmon), rockfish, greenling, Atka mackerel, and Alaska pollack, the least stable among the fish species studied. With regard to the thermo-stability of actomyosin ATPase, it is suggested that the actomyosins of different fish species have become adapted to the respective body temperatures of these species.