TRYPANOSOMA CRUZI: A TOOL FOR MULTISIALYLATION OF β-THIO-GLYCOCLUSTERS

ROSALIA AGUSTI; JOSÉ KOVENSKY; MARÍA EMILIA CANO; ROSA M. DE LEDERKREMER; ALEJANDRO CAGNONI; MARÍA LAURA UHRIG

New Orleans, Louisiana

Simposio; XXVIII International Carbohydrate Symposium; 2016

Multivalent glycoclusters have been synthesized in order to obtain high affinity ligands for specific binding to cellular proteins. Multivalency is most frequently achieved by the simultaneous attachment of several protected sugar fragments to a suitable functionalized scaffold and the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC), also known as the click reaction, has proved to be highly convenient for this purpose. On the other hand, the synthesis of glycoclusters exposing -sialic acid residues remains an active area of research since sialic acid plays an important role in a variety of biological processes including viral and bacterial adhesion. They have a potential for anti-adhesion therapies and would help to elucidate the features involved in carbohydrate-protein interactions.The synthesis of multivalent sialylated glycoclusters is herein addressed by a chemoenzymatic approach using the trans-sialidase of Trypanosom cruzi (TcTS). Multivalent -thio-galactopyranosides and -thio-lactosides were used as acceptor substrates and 3?-sialyllactose as the sialic acid donor. High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was shown to be an excellent technique for the analysis of the reaction products. Different eluting conditions were optimized to allow the simultaneous resolution of the sialylated species, as well as their neutral precursors. The TcTS efficiently transferred sialyl residues to di, tri, tetra and octa -thiogalactosides. In the case of an octavalent thiolactoside, up to six polysialylated compounds could be resolved. Preparative sialylation reactions were performed using the tetravalent and octavalent acceptor substrates. The main sialylated derivatives could be unequivocally assigned by MALDI mass spectrometry. Inhibition of the transfer to the natural substrate, N-acetyllactosamine, was also studied. The octalactoside caused 82 % inhibition of sialic acid transfer when we used equimolar concentrations of donor, acceptor and inhibitor.