Branch specificity of bovine colostrum CMP-sialic acid: N-acetyllactosaminide alpha 2—-6-sialyltransferase. Interaction with biantennary oligosaccharides and glycopeptides of N-glycosylproteins.

D H Joziasse,W E Schiphorst,D H Van Den Eijnden,J A Van Kuik,H Van Halbeek,J F Vliegenthart

doi:10.1016/s0021-9258(20)71155-5

Abstract

By use of 500-MHz 1H NMR spectroscopy, the branch specificity of bovine colostrum CMP-NeuAc:Gal beta 1----4GlcNAc-R alpha 2----6-sialyltransferase towards a biantennary glycopeptide and oligosaccharides of the N-acetyllactosamine type, differing in completeness and structure of their core portion, was investigated. In agreement with earlier reports (Van den Eijnden, D. H., Joziasse, D. H., Dorland, L., Van Halbeek H., Vliegenthart, J. F. G., and Schmid, K. (1980) Biochem. Biophys. Res. Commun. 92, 839-845), it appears that the enzyme strongly prefers the galactosyl residue at the Man alpha 1----3Man branch of the biantennary glycopeptide for attachment of the first sialic acid residue. This branch specificity is fully preserved with the structure (formula; see text) Reduction of the reducing N-acetylglucosaminyl residue in this structure, however, leads to a decreased branch specificity, whereas removal of this residue results in a random attachment of sialic acid to the galactoses at both branches. The decrease in branch specificity is accompanied by a reduction in the rate of sialic acid transfer to the galactose at the alpha 1----3 branch. Our results indicate that the presence of the aforementioned N-acetylglucosaminyl residue is a minimal structural requirement for branch specificity of the sialyltransferase. We propose that in the interaction of the sialyltransferase with its substrates, this N-acetylglucosaminyl residue functions as a recognition site mediating the correct positioning of the substrate on the enzyme.

Highlights

From the Department of Medical Chemistry, Vrije Universiteit, Van der Boechorststraat7, NL-1007 MC Amsterdam, The Netherlands
Commun. 92,839-845), it appears that other partsof the glycan substrate, remote from the point of the enzyme strongly prefers the galactosyl residue at the Manald3Man branch of the biantennary glycopeptide for attachmentof the first sialicacid residue
We propose that in thienteraction of Previously, we have shown that the @-galactosidea 2 4 the sialyltransferase with its substrates, this N-acestyiall-yltransferase from bovine colostrum is able to distinguish between the different branches of bi- and triantennary glycopeptides of the N-acetyllactosamine type [2]

Summary

Introduction

From the Department of Medical Chemistry, Vrije Universiteit, Van der Boechorststraat, NL-1007 MC Amsterdam, The Netherlands. Glycosyltransferases are known to be highlyspecific for. Their acceptor substrate [1]. The acceptor sugar residue is recognized, and the enzymes often interact with. 92,839-845), it appears that other partsof the glycan substrate, remote from the point of the enzyme strongly prefers the galactosyl residue at the Manald3Man branch of the biantennary glycopeptide for attachmentof the first sialicacid residue. Particular featuresof the spatial structure of the glycan play an important role in the recognition of the acceptor by glycosyltransferases

Methods

Results

Conclusion