A novel glycosylphosphatidylinositol in African trypanosomes: A possible catabolic intermediate

Kenneth G. Milne, Michael A.J. Ferguson, Paul T. Englund

Research output: Contribution to journalArticlepeer-review


The major glycosylphosphatidylinositols (GPIs) in African trypanosomes are glycolipid A, the precursor of the variant surface glycoprotein membrane anchor, and glycolipid C, a species identical to glycolipid A except that it contains an acylated inositol. Both glycolipids A and C contain dimyristoyl glycerol and are efficiently labeled with [3H]myristate in a cell-free system. We now report a novel GPI known as lipid X. This GPI is radiolabeled strongly with [3H]palmitate (and very poorly with [3H]myristate or [3H]stearate) in digitonin-permeabilized cells. The structure of lipid X is Man1GlcNAc-(2-O-palmitoyl)-D-myo-inositol-1-HPO4-3(lyso-palmitoylglycerol). Metabolically, lipid X exists as an intermediate, and can be detected only under conditions in which its formation is stimulated (e.g. by EDTA) or its breakdown is inhibited (e.g. by Co2+). Lipid X has not been observed previously because these conditions do not support GPI biosynthesis. We speculate that lipid X is an intermediate in the catabolism of conventional trypanosome GPIs, possibly deriving from breakdown of glycolipid C.

Original languageEnglish (US)
Pages (from-to)1465-1471
Number of pages7
JournalJournal of Biological Chemistry
Issue number3
StatePublished - Jan 15 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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