A UNIQUE, TERMINALLY GLUCOSYLATED OLIGOSACCHARIDE IS A COMMON FEATUREON LEISHMANIA CELL-SURFACES

The structures of N-linked oligosaccharides from various Leishmania li fe-cycle stages and species have been investigated in order to elucida te differences which may be correlated with virulence or tissue tropis ms. The structure of gp63 glycans from L. major log- and stationary-ph ase promastigotes were elucidated and compared with the total membrane associated oligosaccharides from five Leishmania spp. L. major gp63 g lycans from promastigotes in either log or stationary phases of their growth cycle were shown to have two neutral oligosaccharides having Bi o-Gel P4 hydrodynamic volumes of 10.5 and 9.6 glucose units (GU). Sequ ential exoglycosidase digestion, fragmentation by acetolysis and methy lation analysis of hydrazine released glycans; revealed the structure of G9.6 to be a biantennary oligomannose type, having the composition Man(6)GlcNAc(2). These data were confirmed by structural analysis of g p63 oligosaccharides released by digestion with endo-beta-N-acetplgluc osaminidase H (Endo-H) and N-glycanase F. The larger glycan was found to be terminally glucosylated, having the composition GlcMan(6)GlcNAc( 2). These oligosaccharides were found to occupy only two of the three predicted N-linked glycosylation sites in the L. major gp63 molecule, at positions 300 and 407. On comparison with glycans from other Leishm ania spp. and strains, these two oligosaccharides were consistently fo und to be the predominant promastigote structures. Following transform ation to the amastigote stage, alterations in N-linked oligosaccharide s appeared to be less consistent between species. L. m. mexicana amast igotes were found to display the same G10.5 and G9.6 glycans found on promastigotes while L. donovani LV9 amastigotes were found to be devoi d of N-linked glycans. Copyright (C) 1997 Elsevier Science B.V.