| Abstract: | Sphingolipids make up 30 to 40 mole % of the phospholipids found in the surface membrane of Tetrahymena pyriformis NT-1. We have identified the two major classes as non-hydroxy fatty acid-containing ceramide-2-aminoethylphosphonate (NCAEP) and alpha-hydroxy fatty acid-containing ceramide-2-aminoethylphosphonate (HCAEP). Both classes were well represented in cells grown at 39 degrees C. At this temperature their principal long chain bases were n-hexadeca-4-sphingenine and n-nonadeca-4-sphingenine. The major fatty acid of NCAEP from 39 degrees C-grown cells was palmitic acid and that of HCAEP was alpha-hydroxypalmitic acid. Cells grown at 15 degrees C contained NCAEP, but only traces of HCAEP. By analyzing the incorporation of [1-14C]palmitic acid into cells growing isothermally or shifted from 15 degrees C to 39 degrees C, we obtained evidence favoring a direct conversion of NCAEP to HCAEP. This conversion was blocked in cells grown at 15 degrees C, causing an accumulation of NCAEP. Tetrahymena is a useful model system for studying the poorly understood alpha-hydroxylation process that is of critical importance in myelination of animal nervous tissues. |
