The role of glycolipid C in the GPI biosynthetic pathway in Trypanosoma brucei bloodstream forms.

The glycosylphosphatidylinositol (GPI) biosynthetic pathway in Trypanosoma brucei bloodstream forms includes the formation of glycolipid C. This molecule is the inositol-acylated form of the GPI anchor precursor, glycolipid A. There is no evidence for the transfer of glycolipid C to protein in vivo and the role of glycolipid C is unclear. In this paper we show that glycolipid C is not synthesised in the presence of phenylmethylsulphonyl fluoride (PMSF) and that glycolipid C is not an obligatory intermediate on the pathway to the formation of glycolipid A. Using pulse-chase experiments we show that glycolipid A and glycolipid C are in a dynamic equilibrium and we suggest that only the forward reaction (glycolipid A conversion to glycolipid C) is inhibited by PMSF.