While investigating the effect of marine products on cell growth, we found that visceral extracts of Chub mackerel, an ocean fish, had a powerful and dose-dependent apoptosis-inducing effect on a variety of mammalian tumor cells. This activity was strikingly dependent on infection of the C. mackerel with the larval nematode, Anisakis simplex. After purification of the protein responsible for the apoptosis-inducing activity, we cloned the corresponding gene and found it to be a flavoprotein. This protein, termed apoptosis-inducing protein (AIP), was also found to possess an endoplasmic reticulum retention signal (C-terminal KDEL sequence) and H2O2-producing activity, indicating that we had isolated a novel reticuloplasimin with potent apoptosis-inducing activity. AIP was induced in fish only after infection with larval nematode and was localized to capsules that formed around larvae to prevent their migration to host tissues. Our results suggest that AIP may function to impede nematode infection.

From the point of view of high utilization of pearl oyster meat, shellfish protein hydrolysates (SPH) were prepared from pearl oyster meat and three other kinds of shellfish meat by enzymic treatment using proteases. SPH of pearl oyster meat was added to myofibrils from lizard fish and the changes in the state of water in myofibrils associated with dehydration were analyzed on the basis of the sorption isotherm curve and isosteric sorption heat. Involvement of these changes in the denatu ration of myofibrils was investigated with respect to ATPase activity as an indicator and the results were compared with those for SPH of three other kinds of shellfishes.The addition of SPH resulted in a decrease in water activity, an increase in the amount of monolayer or multilayer sorbed water and an increase in the isosteric sorption heat, indicating the changes in the state of water in myofibrils. Furthermore, it was found that SPH has supressive effects on the denaturation of myofibrils resulting from dehydration and there is a correlation be tween the repressive effects and the state of water.These results suggest that the supressive effects on the denaturation are likely to be attributed to the stabilization of the hydrated water surrounding myofibrils by the adittion of SPH.

Advances in the understanding of antibody-antigen interactions and in the production of monoclonal antibodies have outlined possibilities for the broad application of natural immune phenomena to biologic processes occurring beyond the functional realm of the immune response.

From the point of view of high utilization of pearl oyster meat, shellfish protein hydrolysates (SPH) were prepared from pearl oyster meat and three other species of shellfish meat by enzymic treatment using proteases. SPH prepared from each meat was added to lizard fish myofibrils and the changes in the amount of unfrozen water in myofibrils associated with freezing were analyzed by a differential scanning calorimetry. ATPase activity was simultaneously measured.The amount of unfrozen water increased by the addition of each SPH. When SPH was not ad ded to myofibrils, the amount of unfrozen water rapidly decreased during frozen storage, whereas the decrease was moderate in myofibrils with SPH. Meanwhile, the decrease in ATPase activity dur ing frozen storage was a similar tendency to that of the amount of unfrozen water, indicating a close correlation between ATPase activity and the amount of unfrozen water. The present study suggests that the denaturation of myofibrils might be suppressed by the addition of SPH, since SPH construct ed the water molecules resulting in an increase in the amount of unfrozen water.

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