Human platelets have cholesteryl ester hydrolytic activity resulting in esterification of [1-14C]oleate to individual phospholipids of platelets.
Human platelet cholesteryl ester hydrolytic (CEH) activity was determined toward cholesteryl [1-14C]oleate resulting in esterification of [1-14C]oleate to individual platelet phospholipids: choline-containing phospholipids (PC); ethanolamine-containing phospholipids (PE); phosphatidylserine (PS); phosphatidylinositol (PI); and sphingomyelin (SPH). Liberation of [1-14C]oleate and esterification of [1-14C]oleate to platelet phospholipids was enhanced by 100 nM iloprost (a stable analogue of prostacyclin that increases platelet cyclic adenosine monophosphate (c-AMP)), inhibited by 30 microM H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide)) (a specific c-AMP dependent protein kinase (CADPK) inhibitor) and 500 microM 2',5' dideoxyadenosine (DDA) (an inhibitor of iloprost-induced rise in platelet c-AMP), but unaffected by 150 mM choloroquine diphosphate. These observations suggest that the CEH activity is mediated by a CADPK phosphorylation of an enzyme with the phosphorylated state representing the active form of the enzyme and that the CEH activity is extralysosomal.
Barre
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Center for Human Nutrition, University of Texas Southwestern Medical Center at Dallas 75235-9052.
D001792:Blood Platelets / Q000201:enzymology*; D002250:Carbon Radioisotopes; D002788:Cholesterol Esters / Q000378:metabolism*; D016048:Dideoxyadenosine / Q000494:pharmacology; D004951:Esterification; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006801:Humans; D006868:Hydrolysis; D016285:Iloprost / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D019301:Oleic Acid; D009829:Oleic Acids / Q000097:blood*; D010713:Phosphatidylcholines / Q000097:blood; D010714:Phosphatidylethanolamines / Q000097:blood; D010716:Phosphatidylinositols / Q000097:blood; D010718:Phosphatidylserines / Q000097:blood; D010743:Phospholipids / Q000097:blood*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D013109:Sphingomyelins / Q000097:blood; D013449:Sulfonamides
D002250:Carbon Radioisotopes; D002788:Cholesterol Esters; D005230:Fatty Acids, Nonesterified; D007546:Isoquinolines; D009829:Oleic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D010743:Phospholipids; D047428:Protein Kinase Inhibitors; D013109:Sphingomyelins; D013449:Sulfonamides; D019301:Oleic Acid; D016048:Dideoxyadenosine; D016285:Iloprost; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide