Mannosamine can replace glucosamine in glycosylphosphatidylinositols of Plasmodium falciparum in vitro

Mannosamine (2-deoxy-2-amino-D-mannose) is unable to block GP1 biosynthesis in neither parasite development nor GPI biosynthesis were blocked by mannosamine treatment in P. falciparum cultures. Further, it was shown by metabolic labeling with [H-3]mannosamine and subsequent monosaccharide analysis by high pH anion exchange chromatography that mannosamine is converted at a high rate into glucosamine. Both mannosamine and glucosamine are incorporated into P.falciparum glycolipids, but the characterization of mannosamine-labeled glycolipids synthesized in vivo proved difficult. Therefore. it cell-free system was developed to investigate the incorporation of [H-3]mannosamine into glycolipids in P falciparum. It was observed that mannosamine is incorporated in vitro into P falciparum glycolipids, which possess a phosphate group. Chemical (nitrous acid deamination, mild acid hydrolysis and alkaline hydrolysis) and enzymatic (PI-PLC) treatments of [H-3]mannosamine-labeled glycolipids synthesized in vitro showed the presence or GPIs. Further analyses by Bio-Gel P4 size-exclusion chromatography and HPAEC demonstrated the presence of a mannosamine-containing GPI-like structures, where mannosamine is incorporated instead of glucosamine, i.e. Man(3)-ManN-PI, This utilization of rnannosamine is novel and not been described for any other cellular or parasitic system. (c) 2005 Elsevier B.V. All rights reserved.