Glycans, mammalian

Glycans in Information Storage and Transfer Glycans, Mammalian... 

Maras, M., Saelens, X., Laroy, W. et al. (1997) In vitro conversion of the carbohydrate moiety of fungal glycoproteins to mammalian-type oligosaccharides - evidence for JV-acetylglucosaminyltransferase-I-accepting glycans from Trichoderma reesei. European Journal of Biochemistry, 249 (3), 701-707. 

Fig. 15.5. Structures of A/-linked glycans from several different species of parasitic nematodes, illustrating both similarities with mammalian glycans (compare with Figs 15.1 and 15.2) and features unique to nematodes (e.g. tyvelose and PC capping and novel core fucosylation). The filarial nematode glycans are believed to be substituted with charged residues, which are not yet characterized.

Srikrishna, G., Toomre, D.K., Manzi, A., Panneerselvam, K., Freeze, H.H., Varki, A., and Varki, N.M. (2001) A novel anionic modification of N-glycans on mammalian endothelial cells is recognized by activated neutrophils and modulates acute inflammatory responses./. Immunol. 166, 624-632. 

Plant-based production systems are now being used commercially for the synthesis of foreign proteins [1-3]. Post-translational modification in plant cells is similar to that carried out by animal cells plant cells are also able to fold multimeric proteins correctly. The sites of glycosylation on plant-produced mammalian proteins are the same as on the native protein however, processing of N-linked glycans in the secretory pathway of plant cells results in a more diverse array of glycoforms than is produced in animal expression systems [4]. Glycoprotein activity is retained in plant-derived mammalian proteins. 

Fig. 15.3 Plant and mammalian N-glycans have different structures. As illustrated here, a core structure (in gray) is common to plant and mammalian biantennary complex N-glycans. However, differences in the glycan processing machineries in plants and in mammals result in the absence of sialic acids in the terminal position of the antennae and the presence of a bisecting p (1,2) -xylose and of an a(l,3)-fucose residue in PMPs instead of the a(l,6)-fucose linked to the proximal N-acetylglucos-amine of native mammalian N-glycans.

Fig. 15.4 Structure of glycans N-linked to IgG molecules expressed in hybridomas and transgenic plants. Glycans N-linked to plant-derived antibodies are structurally different from their mammalian counterparts. In contrast with antibodies produced in alfalfa, antibodies produced in tobacco plants present a very high glycan heterogeneity.

Plants are not the only heterogeneous expression system to produce potentially immunogenic N-glycans. When antibodies are produced in non-human mammalian... 

Towards Humanized N-glycans on PMPs Through the Expression of Mammalian Glyco-syltransferases in the Plant Golgi Apparatus... 

Fig. 15.7 Glycosylation of an antibody produced in tobacco plants expressing a human 3(l,4)-galactosyltransferase. As illustrated for Guy sl3 in Fig. 15.4, when the monoclonal antibody Mgr48 is produced in wild type tobacco plants (left panel), its glycosylation is structurally different and more heterogeneous than that of its mammalian counterpart (lower panel). When this antibody is produced in tobacco plants expressing the human galactosyltransferase (right panel), 30% of its N-glycans show terminal N-acetyllactosamine sequences identical to those carried by this antibody when it is produced in hybridoma cells.

For other plant-derived antibodies, stability was shown to be similar to mammalian counterparts. For instance, a humanized anti-herpes simplex virus monoclonal antibody (IgGl) was expressed in soybean and showed stability in human semen and cervical mucus over 24 h similar to the antibody obtained from mammalian cell culture. In addition, the plant-derived and mammalian antibodies were tested in a standard neutralization assay with no apparent differences in their ability to neutralize HSV-2. As glycans may play a role in immune exclusion mechanisms in mucus, the diffusion of these monoclonal antibodies in human cerival mucus was tested. No differences were found in terms of the prevention of vaginal HSV-2 transmission in a mouse model, i.e. the plant-derived antibody provided efficient protection against a vaginal inoculum of HSV-2 [58]. This shows that glycosylation differences do not necessarily affect efficacy. 

Plant-made Pharmaceuticals and their Native Mammalian Counterparts Contain Structurally-distinct N-linked Glycans 238... 

Two other structurally characterized transferases have the same or almost the same mode of Mn + coordination as Mn + in Bacillus subtilis glycosyltransferase SpsA described above. A-acetylglucosaminyltransferase I which serves as the gateway from oligomannose to hybrid and complex A-glycans and plays a critical role in mammalian development, has the same active site structure except the Mg + ion and the glycerol are not present. /3 1,3-Glucuronyltransferase I... 

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