Newcastle disease virus contains a linkage-specific glycoprotein sialidase : Application to the localization of sialic acid residues in N-linked oligosaccharides of α1-acid glycoprotein

Abstract

Newcastle disease virus sialidase was found to exhibit strict specificity for hydrolysis of the NeuAcα2→3Gal linkage contained in glycoprotein oligosaccharides both N-linked to asparagine and O-linked to threonine or serine under conditions that left oligosaccharides containing the NeuAc α2→6Gal and NeuAcα2→6GallNAc linkages intact. This was determined, in part, by examining the viral sialidase for its ability to hydrolyze glycoprotein oligosaccharides derivatized with purified sialyltransferases to contain the [14C]NeuAcα2→3Gal, [14C]NeuAcα2→6GalNAc, and [14C]NeuAcα2→6Gal linkages. The viral sialidase was also tested for hydrolysis of the NeuAcα2→3Gal and NeuAcα2→6Gal linkages on the N-linked oligosaccharides of α1-acid glycoprotein. Selective hydrolysis of the NeuAcα2→3Gal linkage was shown by periodate oxidation and by 500-MHz 1H-NMR spectroscopy of native and sialidase-treated glycopeptides. The NMR spectra, together with composition data, further indicated that the NeuAcα2→3Gal and NeuAcα2→6Gal linkages were localized to specific branches of the major tri- and tetraantennary oligosaccharides of α1-acid glycoprotein. The results indicate that the Newcastle disease virus sialidase can initiate the selective degradation of N- linked oligosaccharide branches containing the NeuAcα2→3Gal linkage.