The enzymatic conversion of phospholipid ethanolamine to phospholipid choline in rat liver.

It is known from the work of Elwyn et al. (1) that ethanolamine is incorporated as a unit into the choline molecule during the synthesis de novo of this substance. Du Vigneaud et al. (2, 3) showed that at least some of the methyl groups of choline are derived directly from the methyl group of methionine; and in an earlier communication we provided evidence that all the methyl groups originate from this source (4). Recently, as a result of studies with rat liver in viva (5) and in vitro (6, 7), Bremer and Greenberg proposed that choline is formed by the stepwise transfer of three methyl groups from X-adenosyl methionine to phosphotidyl ethanolamine. The work reported here essentially confirms their findings and offers some further support for the reactions which they formulated.