| Project/Area Number |
10460096
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fisheries chemistry
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| Research Institution | Kitasato University |
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Principal Investigator |
KODAMA Masaaki Kitasato University, School of Fisheries Sciences, Professor, 水産学部, 教授 (40050588)
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| Co-Investigator(Kenkyū-buntansha) |
KOTAKI Yuichi Kitasato University, School of Fisheries Sciences, Associate Professor, 水産学部, 助教授 (30113278)
SATO Shigeru Kitasato University, School of Fisheries Sciences, Associate Professor, 水産学部, 助教授 (20170748)
OGATA Takehiko Kitasato University, Professor, 水産学部, 教授 (00104521)
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| Project Period (FY) |
1998 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥11,500,000 (Direct Cost: ¥11,500,000)
Fiscal Year 2001: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2000: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1998: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Keywords | paralytic shellfish toxin / gonuautoxin / saxitoxin / thiol / protein / scallop / thiol-toxin conjugate / 麻痺性貝毒 / Alexandrium tamarense / A.catenella / 結合タンパク / チオール化合物 / メタロチオネイン / 抗麻痺性貝毒抗体 / 麻痺性貝毒-チオール複合体 / 麻痺性貝毒結合タンパク / 二枚貝 / 毒化機構 / 渦鞭毛藻 / 給餌 / 毒性産菌 |
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| Research Abstract |
We have pointed out in the field survey that bivalves often accumulate PSP toxins during absence of the causative dinoflagellates. The purpose of the present study is to reconsider the mechanism for bivalves to accumulate toxins by the laboratory experiments. Feeding experiments of cultured cells of Alexandrium tamarense to bivalves showed that bivalves released accumulated PSP toxins to the environmental water. However, curious phenomena were observed, that is, 1) bivalves accumulate toxins more than supplied, 2) After the cessation of toxin supply, the sum of accumulated toxins in bivalve and those in the environmental water once decreased, and then increased again. These phenomena are similar to those observed in the field survey. In the reaction in which 11-O-sulfate of gonyautoxins (GTX) is reductively removed by thiols such as glutathione (GSH), stable conjugates of toxins and thiols are found to form. The phenomenon 2) suggests that GTXs bind with GSH of bivalves to form GS-STXs
… More
which cannot be detected by PSP analysis, and then the toxins are released from the conjugates again. However, no significant GS-STXs was detected. It was revealed to be due to a series of the reactions in which GS-STXs is digested by gGTP to form the conjugate of STXs with cysteinyl glycine, and the amino group of cystein decomposes STXs to fluorescent compounds similar to those in alkaline treatment of toxins. When the thin section of toxic scallop digestive gland was stained with antibody against SIX, cytosol of amoebarcytes and membranes surrounding nutrient cells were stained, suggesting that toxins are bound with proteins in these tissues. Protein fractions prepared from the digestive gland by gel filtration gave STXs by treatment with mercaptoethanol, showing that toxins are bound with amino group of cystein residues of proteins in these fractions; On the other hand, GTXs were released when the protein fractions described above are digested with protease, showing that some GTXs are bound with proteins in a different manner from that involved in thiol of cystein residue. Furthermore, fluorescent substances are also observed in the digested protein fractions with protease, indicating that STXs bound with cystein residue are decomposed by digestion ofproteins with protease. These are the first finding on the decomposition of toxins in bivalves in which the enzymes of bivalves are involved. The results of the present study could give a clue for the future study on metabolism of PSP toxins. Less
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