Alex P. Neeleman

Novel Pathways in Complex-Type Oligosaccharide Synthesis

Protein- and lipid-linked complex-type oligosaccharide chains typically contain N-acetyllactosamine (Galβ1→4GlcNAc, LacNAc) units as building blocks of their so called backbone regions. These backbones are the carriers of the terminal structures such as LewisX and sialyl-LewisX, that confer specific properties on the glycoconjugates carrying them.

Effect of saccharides on plasma mediated haemagglutination and in vitro phagocytosis by haemocytes of the snailLymnaea stagnalis

To study the role of lectins in the defence system of the snailLymnaea stagnalis, saccharides were tested for their capacity to inhibit plasma-mediated haemagglutination of trypsinised and fixed mouse red blood cells (M-rbc) and fixed rabbit red blood cells (R-rbc).d-Arabinose,N-acetylneuraminic acid, fucoidan andd-melezitose were good agglutination inhibitors using both types of rbc.d-Fructose, however, stimulated haemagglutination. Based on these results, in vitro phagocytosis assays were performed withd-arabinose (an agglutination inhibitor) andd-fructose (an agglutination stimulator). In co-incubation experiments both sugars inhibited adherence and phagocytosis of M-rbc in a concentration-dependent manner. Adherence and phagocytosis of R-rbc was stimulated at the lowest concentrations of D-arabinose and most concentrations ofd-fructose. Preincubation experiments showed decreased adherence and phagocytosis after preincubation of M-rbc with either sugar. Adherence and phagocytosis of R-rbc was reduced after preincubation of haemocytes withd-fructose. Preincubation of R-rbc had little effect. Our results support former studies indicating the presence of lectins both in the snail plasma and on the haemocytes.

Control and Function of Complex-Type Oligosaccharide Synthesis

Protein N- or O-linked and lipid-linked complex-type oligosaccharide chains are typically based on Ga1β1→4GlcNAc (N-acetyllactosamine, lacNAc) units that serve as backbone structural elements which are built on a core structure (figure 1). Sometimes they contain repeats of these lacNAc units to form so called polylactosaminoglycan chains. These chains are the carriers of terminal, functionally active carbohydrate epitopes such as the sialyl-Lewisx and the oligomeric Lewisx structure. These terminal structures often confer specific biological functions on the glycoconjugates carrying them.