| Budget Amount *help |
¥7,500,000 (Direct Cost: ¥7,500,000)
Fiscal Year 1996: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1995: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Research Abstract |
Seven molecular species of crustacean hyperglycemic hormone (CHH)-family peptides (Pej-SGP-I-VII), a red pigment concentrating hormone (RPCH), and two pigment dispersing hormones (PDHs) were isolated and their complete amino acid sequences determined. Like CHH-family peptides from other crustacean species, the seven CHH-family peptides consisted of 72-77 amino acid residues with six conserved Cys residues.
Six peptides (Pej-SGP-I,II,III,V,VI and VII) showed hyperglycemic activity, when injected into eyestalk-ablated prawns, while Pej-SGP-IV exhibited inhibitory activity in the release of molting hormone (ecdysteroids) by the Y organ cultured in vitro. V and VI also showed a weak molt-inhibiting activity. These peptides were subjected to another assay to assess vitellogenesis-inhibiting activity, in which the effects of these peptides on the protein synthesis were examined by using pieces of developing ovary cultured in vitro. Six peptides with hyperglycemic activity showed inhibitory activity in the protein synthesis. The inhibition was not specific to only synthesis of vitellogenin, but that of all the proteins was inhibited.
All the six peptides with hyperglycemic activity shared carboxyl-terminal amide structure. In order to clarify the impotance of this structure, we tried to synthesize a carboxyl-terminal free peptide by silkworm baculovirus expression system. Double-stranded DNAs encoding Pej-SGP-III and its analog with free carboxyl terminaus were chemically synthesized and inserted into virus DNA,which were injected into 5th instar larvae of the silkworm. But we could not detect any III or its analog in the hemolymph.
The amino acid sequence of RPCH of this species was identical to that of other species thus far obtained. Two PDHs, with three different residues to each other, were equally potent in pigment dispersing activity. Erythrophore was most sensitive to these hormones, xanthophore and melanophore were less sensitive, and leucophore was least sensitive.
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