Document Detail


Glycerolipid synthesis in Chlorella kessleri 11 h. II. Effect of the CO2 concentration during growth.
MedLine Citation:
PMID:  12842193     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In the accompanying paper, we demonstrated that Chlorella kessleri uses prokaryotic and eukaryotic pathways to synthesize sn-1-C18-sn-2-C16 (C18/C16, prokaryotic lipids) and sn-1-C18-sn-2-C18 (C18/C18, eukaryotic lipids) species, respectively, in chloroplast lipids such as monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG). In this study, to examine the effect of CO2 on lipid metabolism, we compared the fatty acid distributions at the sn-1 and sn-2 positions of each major lipid, i.e. MGDG, DGDG, phosphatidylcholine (PC), and phosphatidylethanolamine (PE), and the patterns of incorporation of [14C]acetate into fatty acids and lipids in vivo between cells of C. kessleri grown under ordinary air (low-CO2 cells) and ones grown under CO2-enriched air (high-CO2 cells). Low-CO2 cells, as compared with high-CO2 cells, showed elevated contents of 18:3(9,12,15), especially at both the sn-1 and sn-2 positions of MGDG and DGDG, and also at the sn-2 position of PC and PE. When the cells were labeled with [14C]acetate, slower rates of 18:3 synthesis in the respective major lipids with lower incorporation of 14C into total membrane lipids were observed in low-CO2 cells than in high-CO2 cells. These results thus indicate that the higher unsaturation levels in low-CO2 cells are at least partially due to repressed fatty acid synthesis, which promotes the desaturation of pre-existing fatty acids, rather than to up-regulation of desaturation activity. It was also noted that, in both MGDG and DGDG, the contents of eukaryotic lipids were higher at the expense of prokaryotic lipids in low-CO2 cells than in high-CO2 cells, suggesting relatively greater metabolic flow in the eukaryotic pathway compared to the prokaryotic pathway for galactolipid synthesis in low-CO2 cells. We propose that, together with the repression of fatty acid synthesis, the increased synthesis of C18/C18 species of galactolipids, which are suitable substrates for chloroplast desaturation, through the eukaryotic pathway, contributes to the higher contents of 18:3 in low-CO2 cells than in high-CO2 cells.
Authors:
Norihiro Sato; Mikio Tsuzuki; Akihiko Kawaguchi
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1633     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2003 Jul 
Date Detail:
Created Date:  2003-07-04     Completed Date:  2003-08-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  35-42     Citation Subset:  IM    
Affiliation:
Department of Biology, School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo 192-0392, Japan. nsato@ls.toyaku.ac.jp
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MeSH Terms
Descriptor/Qualifier:
Acetates / metabolism
Carbon Dioxide / metabolism*
Chlorella / growth & development*,  metabolism
Chloroplasts / metabolism
Diglycerides / analysis,  metabolism
Eukaryotic Cells / metabolism
Fatty Acids / analysis,  metabolism
Glycolipids / biosynthesis*
Kinetics
Phosphatidylcholines / analysis,  metabolism
Phosphatidylethanolamines / analysis,  metabolism
Prokaryotic Cells / metabolism
Chemical
Reg. No./Substance:
0/Acetates; 0/Diglycerides; 0/Fatty Acids; 0/Glycolipids; 0/Phosphatidylcholines; 0/Phosphatidylethanolamines; 124-38-9/Carbon Dioxide

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