The Biosynthesis of Sphingosine

DL-Serine-2,3-H3, after subcutaneous injection into rats during the period of active myelination, was utilized in the synthesis of sphingosine. It is concluded that the [alpha]-hydrogen atom of serine is retained during incorporation into sphingosine from the close agreement between the [beta]:[alpha] ratio of tritium in the administered DL-serine-2,3-H3 and the C-l:C-2 ratio of tritium in the isolated sphingosine. Approximately 50 and 25% of the isotope in sphingosine, after administration of DL-serine-3-Cl4, was on carbon atoms 1 and 2, respectively. When tritium oxide was the source of label, the activity in sphingosine, as well as that in cholesterol and sphingolipid fatty acids, was greatest during the period of myelination and diminished soon afterward. The specific activities of sphingosine isolated from each band after chromatography of a C14-labeled sphingolipid mixture were similar. The procedure for reduction of formyl N-benzoylglycine ethyl ester in the synthesis of DL-serine-2,3-H3 was described in detail.