Document Detail

Phosphatidylcholine de novo synthesis and modification are carried out sequentially in HL60 cells: evidence from mass isotopomer distribution analysis.
MedLine Citation:
PMID:  15209508     Owner:  NLM     Status:  MEDLINE    
The traditional (parallel) model of molecular species synthesis of phosphatidylcholine is based on the substrate specificity of two glycerolphosphate acyltransferases. Preformed molecular species of diacylglycerols are then converted to phosphatidylcholine. In this investigation, we used [1,2,3,4-(13)C(4)]palmitate as a tracer to determine the turnover rates of diacylglycerols and phosphatidylcholines. In HL60 cells, the fractional turnover rate is 34.1 +/- 16.6%/h for 1,2-dipalmitoylglycerophosphocholine (16:0,16:0-GPC), which accounts for approximately 10% of total diacylglycerol turnover. The turnover rates of other phosphotidylcholines reflect the primary event of 16:0,16:0-GPC turnover. In addition, the distribution of mass isotopomers is used to study the biosynthesis of diacylglycerols and phosphatidylcholines. On the basis of precursor-product enrichments, we propose a sequential model to account for the synthesis of phosphatidylcholine molecular species. In this model, 1,2-dipalmitoylglycerol is the only molecular species used for the synthesis of phosphatidylcholine. This precursor is converted to 1,2-dipalmitoylglycerophosphocholine, which is then deacylated to provide substrates for chain elongation and/or desaturation. These modified acyl substrates are then reacylated back to form other molecular species. This sequential model is consistent with palmitate being the dominant fatty acid product derived from mammalian fatty acid synthase. It has the advantage of protecting cells from acyl modification by exogenous substrates. Furthermore, this sequence generates only inert 1,2-dipalmitoylglycerol instead of the active diacylglycerol molecular species that contain unsaturated fatty acids.
Kou-Yi Tserng; Ronda L Griffin
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  43     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-06-22     Completed Date:  2004-08-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8125-35     Citation Subset:  IM    
Medical Research Service, Veterans Affairs Medical Center, and Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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MeSH Terms
Carbon Isotopes
Cell Culture Techniques / methods
Culture Media / chemistry
Diglycerides / chemistry,  metabolism
Fatty Acids / biosynthesis,  chemistry
Gas Chromatography-Mass Spectrometry / methods*
HL-60 Cells
Oleic Acid / metabolism
Palmitates / chemistry,  metabolism
Phosphatidylcholines / biosynthesis*,  chemistry,  metabolism
Reg. No./Substance:
0/Carbon Isotopes; 0/Culture Media; 0/Diglycerides; 0/Fatty Acids; 0/Palmitates; 0/Phosphatidylcholines; 112-80-1/Oleic Acid

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