STUDIES ON O-GLYCANS OF PLASMODIUM-FALCIPARUM-INFECTED HUMAN ERYTHROCYTES - EVIDENCE FOR O-GLCNAC AND O-GLCNAC-TRANSFERASE IN MALARIA PARASITES

O-Glycosylation is the major form of protein glycosylation in human er ythrocytes infected with the asexual intraerythrocytic stage of the ma laria parasite, Plasmodium falciparum. This study compares aspects of 0-glycosylation in P falciparum-infected and uninfected erythrocytes. Non-labeled and metabolically glucosamine-labeled 0-glycans were obtai ned from the protein fraction of infected or uninfected erythrocytes b y beta elimination. Additional label was introduced by reduction with sodium borohydride, or by the attachment of radioactive Gal to periphe ral GlcNAc using galactosyltransferase. 2 - 4-times more labeled 0-gly cans were obtained from infected erythrocytes compared to the same num ber of uninfected ones, consistent with additional biosynthesis by the parasite. Our analysis of these 0-glycans showed no significant quali tative divergence between the 0-glycans of the infected and those of t he uninfected red cell. According to preliminary alditol analyses, the 0-glycans of P. falciparum-infected red cells do not contain GalNAc a t their reducing terminus. Moreover, GalNAc was not synthesized by P. falciparum from either Glc, Gal, GlcN or GaIN. At least one 0-glycan f ound in P. falciparum-infected erythrocytes contains GlcNAc at its red ucing terminus. Gel-filtration results had suggested the presence of O -GlcNAc on proteins in the infected erythrocyte. Probing with a synthe tic pentapeptide, we could show that P. falciparum expresses its own O -GlcNAc transferase during intraerythrocytic development. Using this p eptide, the enzyme was characterized to some degree. The localization and function of O-GlcNAc in P. falciparum remains to be elucidated.