抄録
Reconstituted myoglobin of bonito showed a single endothermic peak with higher transition temperature, reflecting a two-state process of structural unfolding. Such a denaturation profile was found to be different from the multi-state process of its holomyoglobin. On the other hand, the denaturation profiles of both holo- and reconstituted myoglobins of sperm whale showed a similar two-state process. The Soret absorbance of both holo- and reconstituted myoglobins of bonito gave rise to similar temperature dependence, but decreased to with a larger extent than that of sperm whale holomyoglobin. The heme pocket environments of both holo- and reconstituted myoglobins of bonito are therefore recognized to be more labile than that of sperm whale holomyoglobin. Also, conformational stability of the tertiary fold of both holo- and reconstituted myoglobins of bonito observed from the temperature dependence of tryptophan fluorescence intensity was found to be considerably lower than that of sperm whale holomyoglobin. The differences in the thermal perturbation profiles of the globin structure between bonito and sperm whale myoglobins could explain the low thermal stability of fish myoglobins.
