In order to clarify the reason why the white muscle fishes are more easily deteriorated byfreezing than the red muscle fishes and the warm blooded animals, the fiuorometric intensity of their myosin solutions was measured in the presence of sodium 8-anilino-1-naphthalene sulfonate. The fluorometric intensity was relatively low for the myosin solutions from the red muscle fishes, such as albacore and yellowfin tuna, and the warm blooded animals, such as pork, whale, chicken and beef, and scarcely increased on freezing overnight at -20°C. The intensity was, however, higher for the solutions from the white muscle fishes, such as angler, Alaska pollack, stone flounder, hair tail,
butterfish
and barracuda, and remarkably increased on freezing. Furthermore, in such the fluorometric behaviors, the pink muscle fishes, such as mullet, saury, Pacific mackerel and Spanish mackerel, showed intermediate between the red muscle fishes and the white muscle fishes. The increment of the fluorometric intensity on freezing was suppressed on the addition of sucrose and Na-glutamate.
These results suggest that in the white muscle fishes, the hydrophobic amino acid residues of myosin molecules are more easily exposed on freezing.
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