Chemoenzymatic synthesis of spacer-linked oligosaccharides for the preparation of neoglycoproteins

In the present work, the combination of chemical and enzymatic methods to o btain neoglycoproteins is described. Three bovine serum albumin (BSA)-conju gates, BSA-[GalNAc alpha-], BSA-[Gal(beta 1-3)GalNAc(alpha-], and BSA-[Neu5 Ac(alpha 2-3)Gal(beta 1-3)GalNAc(alpha-], were prepared, alpha GalNAc deriv atives were galactosylated employing crude P-galactosidase from bovine test es. The use of oversaturated donor solutions (pNP beta Gal) enhanced the yi elds up to 60%. This method was verified using divalent structures as accep ters, that rendered di- and tri-galactosylated products. Further treatment of the disaccharides with CMP-Neu5Ac and alpha 2-3 sialyltransferase from p ork liver led to formation of trisaccharides. Finally, mono-, di-, and tris accharides were coupled to BSA employing a thiolic group introduced into th e protein for Michael addition to a maleinimide group in the spacer-ann of the saccharide components. The results were monitored by HPLC and MALDI-TOF . (C) 1999 Elsevier Science Ltd. All rights reserved.