title: Ethanolamine plasmalogen methylation by rabbit myocardial membranes.
abstract: Enzymatic methylation of alkenylacylglycerophosphoethanolamine to form alkenylacylglycerophosphocholine was observed in rabbit myocardial membranes, and was compared to the corresponding methylation sequence for diacyl substrates. Membranes were incubated with S-adenosyl-L-[methyl-3H]methionine and assayed for incorporation of radioactivity into selected lipids. The rate of incorporation of methyl groups into diacylglycerophosphocholine exceeded that for alkenylacylglycerophosphocholine, 12.0 +/- 3.6 vs. 3.9 +/- 0.7 pmol product formed/mg per h (mean +/- S.D.), even when normalized for ethanolamine substrate concentration (5.7 +/- 1.6 vs. 1.8 +/- 0.4 pmol CH3 incorporated/mumol diradylglycerophosphoethanolamine). Rabbit myocardial phospholipid methyltransferase activity is optimal at basic pH for each substrate, is moderately stimulated by added Ca2+ or Mg2+, and is completely inhibited by S-adenosylhomocysteine. An apparent Km of 0.2 mM for S-adenosylmethionine applies to diacyl- and alkenylacylglycerophosphocholine formation; at low concentrations of methyl donor (0.003 mM), the monomethylated products accumulate.
mesh_terms: D000818:Animals; D007700:Kinetics; D008297:Male; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D008854:Microscopy, Electron; D009206:Myocardium / Q000201:enzymology*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010955:Plasmalogens / Q000378:metabolism*; D011817:Rabbits; D012436:S-Adenosylmethionine / Q000378:metabolism
chemical_list: D010714:Phosphatidylethanolamines; D010743:Phospholipids; D010955:Plasmalogens; D012436:S-Adenosylmethionine; D008780:Methyltransferases