Structural Analysis ofN-Linked Oligosaccharide of Mitogenic Lectin-B from the Roots of Pokeweed (Phytolacca Americana)

The structure of an asparagine (N-) linked oligosaccharide of pokeweed lectin-B (PL-B) and the amino acid sequences around two glycosylation sites were identified. The pyridylamino (PA) oligosaccharide prepared from PL-B was eluted as a single peak on both reversed-phase (RP-) HPLC and size-fractionation (SF-) HPLC, and its structure was estimated to be Man alpha 1-->6(Man alpha 1-->3)(Xyl beta 1-->2) Man beta 1-->4GlcNAc beta 1-->4(Fuc alpha 1-->3)GlcNAc by a combination of component analysis, successive exoglycosidase digestions, IS-MS analysis, and 500 MHz 1H-NMR. Two tryptic glycopeptides were isolated from the reduced and S-pyridylethylated PL-B after gel filtration followed by RP-HPLC, indicating the presence of two glycosylation sites in PL-B. The amino acid sequences around the two glycosylation sites were determined to be Cys-Gly-Val-Asp-Phe-Gly-Asn(CHO)-Arg.