1991 Fiscal Year Final Research Report Summary
Mechanisms for the formation and activation of the latent phenoloxidase complex
| Project/Area Number |
02660101
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
応用生物化学・栄養化学
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| Research Institution | Saga University |
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Principal Investigator |
TSUKAMOTO Takuji Saga Univ., Faculty of Agriculture, Assoc. Professor, 農学部, 助教授 (70136597)
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| Project Period (FY) |
1990 – 1991
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| Keywords | latent phenoloxidase / phenoloxidase / prophenoloxidase / Factor-N / metamorphosis / hemolymph ion concentration / inhibitor / housefly |
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| Research Abstract |
The purpose of this investigation was to establish a molecular and cellular understanding of the mechanisms involved in the activation of latent phenoloxidase during metamorphosis of the housefly. (1)Initially, studies were focussed on the dissociation mechanisms of Factor N from the latent phenoloxidase complex. As a result of these studies, it was found that the dissociation of Factor N from the latent phenoloxidase complex, which is a rate-limitting step in the activation of the latent phenoloxidase complex, was apparently regulated by changes in ion concentration in the hemolymph of housefly prepupae. (2)Prophenoloxidase A was isolated from the purified latent phenoloxidase complex. (3)Cuticle-bound'phenoloxidase was found in pupae of the housefly, and its properties were stud'ied. It is noteworthy that the cuticle-bound phenoloxidase was quite different from hemolymphatic phenoloxidase in terms of substrate specificity. (4)Comparative studies were performed on hemolymphatic phenoloxidase isolated from housefly larvae and phenoloxidase obtained from the latent phenoloxidase complex as a result of activation. Although both enzymes were very similar in terms of molecular weight, subunit structure, optimal pH, optimal temperature, isoelectric point and enzyme kinetics, their N-terminus amino acids were different. (5)Endogenous phenoloxidase inhibitors were isolated from aged pupae of the housefly. The inhibitors were polypeptides which inhibited phenoloxidase activity in a competitive manner. The inhibitors were rich in glycine and cysteine and contained glutamic acid at the N-terminus. Thisconstitutes the first identification of a phenoloxidase inhibitor among the insects and-probably among the invertebrates, as well.
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