Glycosylation of recombinant proteins in transgenic plants

Protein modification by gfycosylation is found in all higher eukaiyotes and plant proteins contain N-linked as well as 0-linked glycans. Variations between the glycans associated with native proteins and recombinant forms may complicate immunotherapy, whatever the heterologous expression s)rstem, and this is not a problem that is specific to recombinant proteins produced in plants. 

However, it is important to understand the differences between plant and mammalian glycans in order to evaluate their relative importance. 

It had previously been demonstrated that the N-linked core hi mannose type glycans have identical structures in plants, mammals, and other organisms (19, 20), which are subsequently modified in a number of steps to complex glycans. Native complex glycans in plant proteins can be quite heterogeneous. 

Nevertheless, for systemic applications, it may be necessary to remove the complex glycans, or to alter the heavy chain sequence to remove the sites for N-linked glycosylation. An alternative, more elegant approach is also being developed using mutant plants that lack enzymes involved in the complex glycosylation pathway (22). 

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