The Incorporation of Ethanolamine and Methionine into Sphingomyelin in Ehrlich Ascites Tumor Cells

Abstract

Using Ehrlich ascites tumor cells, it was shown that choline-1,2-14C, and also ethanolamine-2-14C and methionine(methyl-3H) were incorporated into sphingomyelin. Further experiments revealed that ethanolamine-2-14C was incorporated into phosphorylethanolamine, cytidine 5′-diphosphate ethanolamine, phosphatidylethanolamine, phosphatidylcholine, cytidine 5′-diphosphate choline, and sphingomyelin, and that methionine(methyl-3H) was incorporated into the three latter compounds. The specific activities of these compounds were found to decrease in the order shown above when the tumor cells were incubated with either ethanolamine or methionine. When microsomal preparations from the tumor cells were incubated with radioactive phosphatidylcholine, radioactivity was observed in cytidine 5′-diphosphate choline and diglyceride. It is thus proposed that the following pathways of phospholipid biosynthesis are operative in Ehrlich ascites cells:[Formula: see text]The operation of these pathways would explain the observed incorporation of both ethanolamine and methionine into sphingomyelin.