Fast skeletal myosins were isolated from carp acclimated to 10 and 30 degrees C, and their structural and enzymatic properties were compared. Myosins in 0.5 M KCl were subjected to limited proteolysis by using various proteases including alpha-chymotrypsin, trypsin, and papain, and different SDS-PAGE patterns were seen for the 10- and 30 degrees C-acclimated myosins in all cases. Myosin subfragment-1 (S1) prepared from the 10 degrees C-acclimated myosin by alpha-chymotryptic digestion in 0.12 M NaCl showed higher acto-S1 Mg(2+)-ATPase activity and lower thermostability than S1 from the warm-acclimated myosin. The peptide maps and ATP-induced spectral changes of tryptophan fluorescence also showed an obvious difference between the two types of S1. Temperature acclimation further caused changes in the rod region of myosin, since the apparent sizes of light meromyosin were different from each other for the two types of myosin. Myosin from carp acclimated to 20 degrees C showed intermediate properties between those of the 10- and 30 degrees C-acclimated myosins. Myosin isoforms might be expressed in a temperature-dependent manner to compensate for the effect of seasonal environmental temperature variation on swimming ability.
Arai" (washing) is a traditional cooking method of fish preparation in Japan. Carp muscle slices were washed in water (49°C for 15 set, or 0°C for 10 min), and examined for physical and biochemical changes. At 49"C, rigor-mortis was accelerated, resulting in a marked decrease of muscle slice thickness. ATP degradation proceeded faster at 49°C than at 0°C. Arai treatment at 49°C increased myofibrillar M$+ -ATPase activity 8-9 times in the absence of Ca2+, but did not affect activity in the presence of Ca*+ as much, giving only a 1.2 times increase.
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