A unique, terminally glucosylated oligosaccharide is a common feature on Leishmania cell surfaces

The structures of N-linked oligosaccharides from various Leishmania life-cycle stages and species have been investigated in order to elucidate differences which may be correlated with virulence or tissue tropisms. The structure of gp63 glycans from L major log- and stationary-phase promastigotes were elucidated and compared with the total membrane associated oligosaccharides from five Leishmania spp. L. major gp63 glycans from promastigotes in either log or stationary phases of their growth cycle were shown to have two neutral oligosaccharides having Bio-Gel P4 hydrodynamic volumes of 10.5 and 9.6 glucose units (GU). Sequential exoglycosidase digestion, fragmentation by acetolysis and methylation analysis of hydrazine released glycans, revealed the structure of G9.6 to be a biantennary oligomannose type, having the composition Man6GlcNAc2. These data were confirmed by structural analysis of gp63 oligosaccharides released by digestion with endo-beta-N-acetylglucosaminidase H (Endo-H) and N-glycanase F. The larger glycan was found to be terminally glucosylated, having the composition GlcMan6GlcNAc2. 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 Leishmania spp. and strains, these two oligosaccharides were consistently found to be the predominant promastigote structures. Following transformation to the amastigote stage, alterations in N-linked oligosaccharides appeared to be less consistent between species. L. m. mexicana amastigotes were found to display the same G10.5 and G9.6 glycans found on promastigotes while L. donovani LV9 amastigotes were found to be devoid of N-linked glycans.