Glycosylation of recombinant ancrod from Agkistrodon rhodostoma after expression in mouse epithelial cells

The thrombin-like serine protease ancrod from the Malayan pit viper Agkistrodon rhodostoma was expressed in mouse epithelial cells (C127). Oligosaccharide constituents were liberated from tryptic glycopeptides by treatment with peptide-N-4-(N-acetyl-beta-glucosaminyl)asparagine amidase F. Neutral oligosaccharide alditols obtained after reduction and enzymic desialylation were separated by two-dimensional HPLC and characterized by methylation analysis, liquid secondary-ion mass spectrometry, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and sequential degradation with exoglycosidases. In contrast to natural ancrod, the recombinant glycoprotein carries exclusively diantennary, triantennary and tetraantennary N-glycans with Gal beta 4GlcNAc beta (type-2) antennae which were, in part, further substituted by host-cell-specific structural elements such as Gal alpha 3 residues or N-acetyllactosamine repeats. As a characteristic feature, a substantial proportion of the oligosaccharides bears a GalNAc beta 4GlcNAc antenna. Studies at the level of individual N-glycosylation sites demonstrated that glycans with N,N'-diacetyllactosediamine units are not specifically attached but occur at all sites in varying amounts. Hence, the putative recognition signal (Pro70-Lys-Lys) for glycoprotein hormone N-acetylgalactosaminyltransferase, present in this glycoprotein in close proximity to Asn79, does not convey site-specific transfer of GalNAc residues in these cells.