Identification of endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol in myocardium and its effective utilization by choline phosphotransferase.
Recently we have identified a novel choline and ethanolamine specific phospholipase C in myocardium and have hypothesized that this enzyme is responsible for the introduction of the vinyl ether linkage into plasmenylcholine by shuttling 1-O-alk-1'-enyl-2-acyl-sn-glycerol fragments from plasmenylethanolamine to plasmenylcholine (Wolf, R. A., and Gross, R. W. (1985) J. Biol. Chem. 260, 7295-7303). The present study demonstrates that rabbit myocardium contains endogenous 1-O-hexadec-1'-enyl-2-acyl-sn-glycerol (0.46 micrograms/g) and that these moieties are selectively utilized by myocardial choline phosphotransferase to generate plasmenylcholine. The apparent Michaelis constant of CDP-choline for microsomal choline phosphotransferase was 9 microM with a corresponding Vmax of 18 pmol/mg.min utilizing endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol as substrate. The flux of CDP-choline into plasmenylcholine or phosphatidylcholine was similar despite the fact that the mass of endogenous 1,2-diacyl-sn-glycerol was over 20 times the mass of endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol. Augmentation of endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol content by pretreatment of myocardial microsomes with exogenous phospholipase C resulted in an 8-fold increase in plasmenylcholine synthesis. The results suggest that myocardial plasmenylcholine biosynthesis occurs by polar head group remodeling utilizing endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol as a synthetic intermediate. Flux through this pathway is likely regulated by physiologic increments in endogenous 1-O-alk-1'-enyl-2-acyl-sn-glycerol content and cytosolic CDP-choline concentration.
Ford
D A
DA
Department of Medicine, Washington University, St. Louis, Missouri 63110.
Gross
R W
RW
D000818:Animals; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D003566:Cytidine Diphosphate Choline / Q000378:metabolism; D002798:Diacylglycerol Cholinephosphotransferase / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008861:Microsomes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D010742:Phospholipid Ethers / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism*; D010955:Plasmalogens / Q000096:biosynthesis; D011817:Rabbits; D010738:Type C Phospholipases / Q000378:metabolism*
D010742:Phospholipid Ethers; D010955:Plasmalogens; C032459:choline plasmalogens; D003566:Cytidine Diphosphate Choline; D010770:Phosphotransferases; D002798:Diacylglycerol Cholinephosphotransferase; D010738:Type C Phospholipases