Biosynthesis of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor and a hypotensive lipid) by cholinephosphotransferase in various rat tissues

Biochim Biophys Acta. 1981 Feb 23;663(2):545-56. doi: 10.1016/0005-2760(81)90182-x.


The unique alkyl phospholipid, 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine, has been reported to exhibit powerful antihypertensive activity (Blank, M.L., Snyder, F., Byers, L.W., Brooks, B. and Muirhead, E.E. (1979) Biochem. Biophys. Res. Commun. 90, 1194-1200) and appears to be an extremely potent platelet-activating factor (Demopoulos, C.A., Pinckard, R.N. and Hanahan, D.J. (1979) J. Biol. Chem. 254, 9355-9358). In the present study, microsomal preparations from several rat tissues were found to catalyze the synthesis of 1-alkyl-1-acetyl-sn-glycero-3-phosphocholine by 1-alkyl-2-acetyl-sn-glycerol:CDPcholine cholinephosphotransferase reaction. Optimal conditions to measure enzyme activity were established. A subcellular survey of this cholinephosphotransferase activity showed that the enzyme was of microsomal origin. Enzyme activity was found in microsomes from several tissues; however, spleen has the highest activity of the tissues examined. Three different species of 1-alkyl-2-acetyl-sn-glycerol were all found to be substrates. The 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine synthesized in the microsomes could be hydrolyzed by adding the 100,000 x g supernatant fraction to the incubation medium. The optimum pH for formation of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine was 8.0, which was different from the pH optimum of 8.5 observed for the long-chain diacylglycerol cholinephosphotransferases. Activity of cholinephosphotransferase towards 1-alkyl-2-acetyl-sn-glycerol was slightly enhanced and stabilized by dithiothreitol, whereas the activity towards a diacylglycerol was inhibited by dithiothreitol. The possible involvement of two different enzymes in the conversion of 1-alkyl-2-acetyl-sn-glycerol and diacylglycerol to their respective phospholipid products is discussed.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antihypertensive Agents / metabolism
  • Blood Platelets / drug effects
  • Cytosol / metabolism
  • Diacylglycerol Cholinephosphotransferase / metabolism*
  • Diglycerides / metabolism
  • Lysophosphatidylcholines / biosynthesis*
  • Male
  • Microsomes / enzymology
  • Microsomes, Liver / enzymology*
  • Phosphotransferases / metabolism*
  • Platelet Activating Factor
  • Rats
  • Spleen / enzymology*
  • Substrate Specificity


  • Antihypertensive Agents
  • Diglycerides
  • Lysophosphatidylcholines
  • Platelet Activating Factor
  • Phosphotransferases
  • Diacylglycerol Cholinephosphotransferase