The biosynthesis of choline and its relation to phospholipid metabolism

Studies on the Phospholipid Metabolism in Choline-Deficient Guinea Pigs

“…Phosphatidylethanolamine has been be lieved to be methylated stepwisely with s adenosylmethionine as the methyl donor in rat liver (17)(18)(19), it was suggested that the transfer of the second and the third methyl groups to the partially methylated intermediate phosphatides was considerably more rapid than that of the first methyl group to phosphatidyl ethanolamine. Labeled MME or DME were reported to be incorporated into phosphatides and then methylated to form lecithin in rat liver preparations (18,(20)(21)(22)(23) into phosphatidyl-MME, -DME and lecithin of liver slices Amount of methyl group incorporated into each of the three phospholipid bases, MME, DME and choline (CHOL), was calculated from total incorpora tion (Table 8) and percent distribution of radioactivity (Table 9).…”

Stimulation by vasopressin and angiotensin of phospholipid methyltransferase in isolated rat hepatocytes

“…Phosphatidylcholine can be synthesized either by transcholination [2] or by transmethytation [3]. The transmethylation pathway involves the addition of 3 methyl groups to the polar head of phosphatidylethanolamine, the methyl donor being S-adenosyl-L-methionine.…”

The incorporation of the phosphate esters of N-substituted aminoethanols into the phospholipids of brain and liver

“…Further, Wilson, Gibson & Udenfriend (1960) demonstrated that the labelling of lipid ethanolamine from L- [3-l4C]serine by liver and brain slices was not significantly diminished by adding unlabelled ethanolamine or phosphorylethanolamine. The methylation of phosphatidylethanolamine to phos-* Present address: The Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland. phatidylcholine by S-adenosylmethionine in vivo was also indicated by the experiments of Bremer et al (1960). So far the introduction of the first methyl group into phosphatidylethanolamine has not been demonstrated in vitro though the methylation of phosphatidylmonomethylaminoethanol and phosphatidyldimethylaminoethanol by S-adenosylmethionine in the presence of different liver preparations has been successfully accomplished (Artom & Lofland, 1960;Bremer & Greenberg, 1961; Artom, 1964;Rehbinder & Greenberg, 1965).…”

“…Thus, although it has been known for some time that injected L-serine can give rise to ethanolamine in liver (Arnstein, 1951), Bremer, Figard & Greenberg (1960) showed that L-[3-14C]serine labelled lipid ethanolamine better than the free phosphorylethanolamine or CDP-ethanolamine, suggesting that the last two compounds were not intermediates. Further, Wilson, Gibson & Udenfriend (1960) demonstrated that the labelling of lipid ethanolamine from L- [3-l4C]serine by liver and brain slices was not significantly diminished by adding unlabelled ethanolamine or phosphorylethanolamine.…”