Identification of a lysophospholipase C that may be responsible for the biosynthesis of choline plasmalogens by Madin-Darby canine kidney cells.
The biosynthesis of choline plasmalogens was investigated in Madin-Darby canine kidney cells to determine the source of the vinyl ether linkage. 1-O-[3H] Alk-1'-enyl-2-lyso-sn-glycero-3-phosphoethanolamine was a better precursor than 1-O-[3H]alkyl-2-lyso-sn-glycero-3-phosphocholine for the synthesis of 1-O-[3H]alk-1'-enyl-2-acyl-sn-glycero-3-phosphocholine; this suggests that the vinyl ether linkage in choline phosphoglycerides originates from ethanolamine plasmalogens. The contribution of N-methylation and base exchange enzymes to choline plasmalogen biosynthesis was assessed using 1-O-[3H]alkenyl-2-lyso-sn-glycero-3-[32P]phosphoethanolamine. While 1-O-[3H]alkenyl-2-acyl-sn-glycero-3-phosphocholine was formed from this precursor, the 32P was lost indicating that N-methylation and base exchange enzymes do not contribute significantly to the synthesis of choline plasmalogens. The conversion of a phosphono analog of 1-O-[3H]alkyl-2-lyso-sn-glycero-3-phosphoethanolamine, which is resistant to phospholipase D hydrolysis, to 1-O-[3H]alkenyl-2-acyl-sn-glycero-2-phosphocholine was observed demonstrating that phospholipase D is not required for choline plasmalogen biosynthesis. A Mg(2+)-dependent lysophospholipase C activity was detected in microsomes that actively hydrolyzed ether-linked lysophosphoglycerides as well as the lysophosphono analog. To assess the role of lysophospholipase C in shuttling 1-O-alk-1'-enyl-sn-glycerol (alkenylglycerol) from ethanolamine plasmalogens to choline plasmalogens, cells prelabeled with 1-O-[3H]alkenyl-2-lyso-sn-glycero-3-phosphoethanolamine were treated with 12-O-tetradecanoylphorbol-13-acetate. This resulted in the rapid deacylation of 1-O-[3H]alkenyl-2-acyl-sn-glycero-3-phosphoethanolamine to 1-O-[3H]alkenyl-2-lyso-sn-glycero-3-phosphoethanolamine and the subsequent generation of 1-O-[3H]alkenylglycerol. A concomitant 2-3-fold increase in 1-O-[3H]alkenyl-2-acyl-sn-glycero-3-phosphocholine was observed. These studies suggest that the alkenyl linkage in choline phosphoglycerides may originate from 1-O-alkenyl-2-lyso-sn-glycero-3-phosphoethanolamine through an enzymatic pathway involving lysophospholipase C to generate alkenylglycerol that is subsequently converted to choline plasmalogens.
Strum
J C
JC
Department of Biochemistry, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1016.
Daniel
L W
LW
D000818:Animals; D002460:Cell Line; D004285:Dogs; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008245:Lysophospholipase / Q000378:metabolism*; D008246:Lysophospholipids / Q000302:isolation & purification / Q000378:metabolism*; D008954:Models, Biological; D010955:Plasmalogens / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014316:Tritium
D008246:Lysophospholipids; D010955:Plasmalogens; C032459:choline plasmalogens; C008301:lysophosphatidylethanolamine; D014316:Tritium; D008245:Lysophospholipase; D013755:Tetradecanoylphorbol Acetate