THE INCORPORATION, MODIFICATION AND TURNOVER OF FATTY-ACIDS IN ADULT SCHISTOSOMA-MANSONI

Schistosoma mansoni is known to be unable to synthesize fatty acids an d sterols de novo, but the parasite is capable of synthesizing phospho lipids and triacylglycerols from precursors obtained from the host. Th e present study focuses on the dynamics of the incorporation of fatty acids in adult parasites. This study showed that fatty acids were rapi dly metabolized into complex lipids and that oleate (18:1) was efficie ntly converted to eicosenoate (20:1) by chain elongation, whereas palm itate was not elongated at an appreciable rate. This chain elongation mainly involved fatty acids that were previously esterified to complex lipids. Furthermore it was shown that in adult parasites triacylglyce rols do not serve as fatty-acyl donors in phospholipid synthesis as ha d been suggested to be the case in schistosomula, because: (1) immedia tely after pulse-labelling the specific activity of fatty acids in pho spholipids was higher than in triacylglycerols; and (2) the specific a ctivity of eicosenoate, which had been formed by chain elongation of i ncorporated oleate, was higher in phospholipids than in triacylglycero ls. Fatty acids that were esterified to phospholipids had a high turno ver, in contrast to fatty acids esterified to triacylglycerols, which persisted for extended periods of time in this lipid class (days rathe r than hours). (C) 1997 Elsevier Science B.V.