Sites of asparagine-linked oligosaccharides in porcine 32kDa enamelin

The 32 kDa enamelin protein isolated from developing porcine enamel was pre viously shown to contain eight different asparagine-linked oligosaccharides . However, only three consensus attachment sites were evident in this prote in. In this study, glycopeptides containing all three potential glycosylati on sites (72-Asn, 79-Asn and 91-Asn) were purified from 32 kDa enamelin. Th e oligosaccharides were isolated from each glycopeptide following digestion with N-oligosaccharide glycopeptidase, labeled with 2-aminopyridine at the reducing ends, and then characterized by reverse phase HPLC. All three pot ential sites were found to be glycosylated heterogeneously (i.e., five bian tennary complexes at 72-Asn, two biantennary complexes at 79-Asn, three tri antennary complexes at 91-Asn), accounting for all eight oligosaccharides c haracterized previously, These results indicate that 32 kDa enamelin has a complex pattern of asparagine-linked glycosylation localized within a small region (20 residues) of the protein, The functional significance of this g lycosylation remains to be established.