Sialylation by recombinant trans-sialidase of the synthesized oligosaccharides, O-linked in Trypanosoma cruzi glycoproteins

ROSALIA AGUSTI; VERONICA M. MENDOZA; M. EUGENIA GIORGI; CAROLA GALLO-RODRIGUEZ; ROSA M. DE LEDERKREMER

Pinamar, Buenos Aires

Congreso; SAIB 41th Annual Meeting; 2005

SAIB

The mucin-like glycoproteins of T. cruzi have novel O-linked oligosaccharides which are acceptors of sialic acid in the trans-sialidase (TcTS) reaction. This process is involved in infection and pathogenesis. The O-chains may be derived from the two cores, Galp(b1?¨4)GlcNAc or Galf(b1?¨4)GlcNAc by further branching with various units of Galf and/or Galp. The presence of galactofuranose is related to the lineage and was found in the G, DM28C and Tulahuen strains of T. cruzi. We have chemically synthesized the oligosaccharides containing 3-5 sugar units. The acceptor properties were studied in order to correlate their structure with the ability to act as substrates. Recombinant TcTS (A. C. C. Frasch (UNSAM)), and sialyllactose as donor were used. The reactions were analyzed by HPAEC-PAD. The Km values were calculated for the free sugars and the benzyl glycosides. The highest affinity was shown by the trisaccharide. The pentasaccharide, the major O-linked sugar in the mucins, presents two terminal b-D-Galp for possible sialylation. A preparative TS reaction was performed with the benzyl glycoside of the pentasaccharide. One of the two external Galp units was selectively sialylated, as shown by NMR spectroscopy.