PHOSPHOLIPASE CLEAVAGE OF GLYCOSYLPHOSPHATIDYLINOSITOL RECONSTITUTED IN LIPOSOMAL MEMBRANES

Glycosylphosphatidylinositol (GPI) purified from rat liver lipids was incorporated into lipid bilayers of defined compositions, in the form of large unilamellar vesicles, The CPI concentration in the bilayers w as kept constant at 25 mole%, whereas the remaining lipids being phosp hatidylcholine, phosphastidylethanolamine, sphingomyelin and/or choles terol weft? varied, The resulting liposomes consisted of spherical ves icles, approximately 100 nm in diameter, that could keep their aqueous contents separated from the extravesicular medium. When these liposom es mere treated with either Bacillus cereus phosphatidylinositol-phosp holipase C, Trypanosoma brucei GPI-phospholipase C, or bovine serum GP I-phosphalipase D, GPI was hydrolyzed at different rates, depending on the enzyme and the bilayer lipid composition. These observations open the way to biophysical and biochemical studies of enzymic GPI cleavag e under defined conditions, Extensive GPI hydrolysis was observed in c ertain eases that could allow the use of these systems for the prepara tion of inositol phosphoglycans, proposed second messengers of a wide variety of hormones, cytokines and growth factors. (C) 1998 Federation of European Biochemical Societies.