1991 Fiscal Year Final Research Report Summary
Enzyme system for the production of signal trunsmitters in human platelets
| Project/Area Number |
02453126
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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 |
応用生物化学・栄養化学
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| Research Institution | Kyoto University |
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Principal Investigator |
KITO Makoto Research Institute for Food Science, Kyoto University, Professor, 食糧料学研究所, 教授 (60027183)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Human platelets / Phospholipase C / Diacylglycerol lipase / Arachidonic acid / Phosphatidylinositol-4, 5-bisphosphate |
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| Research Abstract |
In collagen-activated human platelets, elevation of cytosolic Ca^<2+> 2 level was not caused by collagen itself, but by thromboxane A_2, Of Which precursor arachidonate was produced via collagen-induced inositot lipid metabolism. The metabolism was catalyzed by cooperation of inositol lipid-spercific phospholipase C, diacylglycerol lipase and monoacylglycerol lipase.
Two types of cytosolic phospholipase C(PLC) specific for phosphoinositides were purified from human platelets. The molecular masses of the purified en2ymes were 440 ind 290 KDa. These en2Ymes were concluded to be respectively a trimer and a dimer of homologous 146 KDa polypeptides. The 146 KDa polypeptide may be an immunologically novel isozyme among the 140-150 KDa PLC isozymes. Both enzymes hydrolyzed phosphatidylinositol and phosphatidylinositol-4, 5-bisphosphate in a Ca^<2+> 2-dependent manner.
Diicylglycerof lipase was partially purified from human platelet membranes. The enzyme catalyzed the reaction around neutral pH even in the absence of Ca^<2+>.
Purification and properties of human platelet monoacylglycerof lipase will be examined in near future.
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