Journal of Lipid Research, Vol 32, 703-712, Copyright © 1991 by Lipid Research, Inc.
Head group precursors modify phospholipid synthesis in Schistosoma mansoni
ST Furlong and JP Caulfield
Department of Medicine, Harvard Medical School, Boston, MA 02115.
The two predominant phospholipids in schistosomula of Schistosoma mansoni
are phosphatidylcholine (PC) and phosphatidylethanolamine (PE) which are
found in a molar ratio of 0.52 (PE/PC). The incorporation of four fatty
acids (arachidonic, myristic, oleic, and palmitic) and glycerol into
phospholipids of schistosomula was measured. In two different media (one
containing ethanolamine, the other without), all four fatty acids were
predominantly incorporated into PC with a PE/PC ratio of approximately 0.1
in a 90-min label. After a 24-h chase, PC remained the predominant labeled
phospholipid but the fatty acid- labeled PE/PC ratio increased slightly,
the specific activity of labeled neutral lipids decreased, and the specific
activity of labeled PE increased. Glycerol was incorporated with a ratio of
0.55 in the presence of ethanolamine but only 0.19 in its absence.
Schistosomula also incorporate fatty acids into
phosphatidylmonomethylethanolamine (PMME) and
phosphatidyldimethylethanolamine (PDME) at rates intermediate to that into
PE and PC in the presence of the respective head group precursor; this
incorporation was inhibited by choline. Relative to PC, oleic acid is
incorporated into PE, PMME, and PDME at rates higher than for palmitic
acid. These results suggest that schistosomula possess acyltransferase(s)
with head group specificity and that acyl chains are transferred from
neutral lipids to phospholipids over time.