Biosynthesis of phospholipid molecular species in isolated liver cells studied by combining fatty acid substrates esterified in the sn-1 and sn-2 positions.
The simultaneous incorporation of a saturated fatty acid in the sn-1 position and an unsaturated fatty acid in the sn-2 position in phosphatidylcholine (PC) and ethanolamine (PE) was studied in isolated liver cells. We combined a saturated fatty acid, 16:0 or 18:0 and an unsaturated fatty acid substrate, 18:2,n-6 or 20:4,n-6. In this situation the saturated fatty acids were preferentially oxidized and the unsaturated fatty acids were preferentially esterified in PL and TG. Addition of unlabelled 16:0 increased the incorporation of [14C]18:2 in 16:0-18:2 in PC and PE, reduced the incorporation in 18:2-18:2 but did not reduce the incorporation in 18:0-18:2. 18:0 increased the esterification of [14C]18:2 in 18:0-18:2, reduced the incorporation in 18:2-18:2 but did not reduce the incorporation in 16:0-18:2. The latter is the dominating 14C-labelled species formed from [14C]18:2 also in the presence of unlabelled 18:0. Addition of 20:4 stimulated the incorporation of [14C]16:0 in 16:0-20:4 and markedly reduced the formation of 16:0-18:2, 16:0-18:1 and 16:0-22:6. Addition of 18:2 increased the incorporation of [14C]16:0 in 16:0-18:2 and reduced the formation of 16:0-20:4 and 16:0-18:1. It is concluded that the unsaturated fatty acids 18:2 or 20:4 have a stronger impact on the synthesis of phospholipid molecular species than the saturated fatty acids 16:0 or 18:0 have. Thus 20:4,n-6 and 18:2,n-6 are able to direct available [14C]16:0 or [14C]18:0 to the sn-1 position. 16:0 and 18:0 are not in the same way able to direct [14C]18:2,n-6 to the synthesis of 16:0-18:2 or 18:0-18:2 at the expense of other 14C-labelled molecular species.
Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway.
B
B
Woldseth
B O
BO
Christophersen
D000818:Animals; D016718:Arachidonic Acid / Q000737:chemistry* / Q000378:metabolism; D002478:Cells, Cultured; D004952:Esters / Q000378:metabolism*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000737:chemistry* / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000737:chemistry* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D010714:Phosphatidylethanolamines / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar
D004952:Esters; D008041:Linoleic Acids; D010169:Palmitic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D016718:Arachidonic Acid; D019308:Palmitic Acid; D019787:Linoleic Acid