| Research Abstract |
In the past research, it has been clarified that the C-terminal tri-peptide amide (PRL-NH_2) of diapause hormone (DH) is the minimum structure for biological activity.
In the present study, the role of the side-chain group of DH for the activity expression was analyzed by preparing the DH analogs and by analyzing the biological activity. The results are : 1) the amide structure is indispensable for the activity, 2) the positively charged side-chain of Arg of PRL-NH_2 is essential, 3) modification of PRL-NH_2 with acyl group enhances the activity, 4) palmitoyl-NH_2 and stearoyl-PRL-NH_2 show the strongest activity among the tested derivatives.
While, the lipophilic peptide isolated from the heads of silkmoths enhanced the activity of DH.The fragment analog of the peptide showed interesting effect on enzymic digestion of DH.It protected the hormone from the digestion by interacting not with the enzyme but with the substrate, DH.Another peptide showing the similar synergistic effect on DH action was searched for in the other arthropods, and one protein, Pb CP-12.7, was isolated from the shell of the shrimp, Pandalus borealis, and its unique structure and lipophilic nature were clarified. These results offered the hint to improve the method for dosage of the hormone.
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