| Project/Area Number |
06454176
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pathological medical chemistry
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| Research Institution | Hamamatsu University School of Medicine |
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Principal Investigator |
ICHIYAMA Arata Hamamatsu University School of Medicine, First Department of Biochemistry, Professor, 医学部, 教授 (90025601)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Keiji The University of Tokushima, Institute for Enzyme Research, Associate Professor, 酵素科学研究センター, 助教授 (10108871)
SUZUKI Toshiaki Hamamatsu University School of Medicine, First Department of Biochemistry, Assit, 医学部, 助手 (90252171)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥7,200,000 (Direct Cost: ¥7,200,000)
Fiscal Year 1995: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1994: ¥5,300,000 (Direct Cost: ¥5,300,000)
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| Keywords | serine : pyruvate aminotransferase / alanine : glyoxylate aminotransferase / primary hyperoxaluria type 1 / mutant protein / energy-dependent proteolysis / 26S proteasomes / reticulocyte lysate / yeast mutant pre1-1 / エネルギー症候性蛋白質分解 / 酵母変異株prel-1 / 蓚酸 / エネルギー依存性蛋白分解 / ユビキチン系 |
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| Research Abstract |
We recently studied a primary hyperoxaluria type 1 case who belongs to the ENZ^-/CRM^- class, and his serine : pyruvate/alanine : glyoxylate aminotransferase (SPT/AGT) gene was found to have a homogygous point mutation in the middle of the coding region (a T to C mutation resulting in a Ser to Pro substitution at residue 205). Available evidence suggested that the enzyme deficiency is due to neither a defect in transcription nor one in translation, but is due, at least in part, to instability of the mutant SPT/AGT protein in cells. The mutant SPT/AGT was also degraded faster than normal in an in vitro system involving a rabbit reticulocyte lysate, and this reaction required ATP and Mg^<2+>. A well characterized ATP-hydrolysis-dependent proteolytic machinary in reticulocyte lysates is the ubiquitin-proteasome system, but immunodepletion of proreasomes or inclusion in the reaction mixture of peptide aldehyde proteasome inhibitors had no effect on the degradation of the mutant SPT/AGT in a reticulocyte lysate. In addition, the mutant SPT/AGT was not stabilized in a yeast mutant (per1-1) with defective proteasomes. These results indicate that the inherited mutant SPT/AGT is degraded ATP-hydrolysis-dependently without involvement of proteasomes. It is thus suggested that an energy-dependent proteolytic pathway other than that involving proteasomes participates in selective elimination of abnormal proteins generated in genetic disorders.
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