Molecular cloning and heterologous expression of β1,2-xylosyltransferase and core α1,3-fucosyltransferase from maize

Maize is considered a promising alternative production system for pharmaceutically relevant proteins. However, like in all other plant species asparagine-linked oligosaccharides of maize glycoproteins are modified with beta 1,2-xylose and core alpha 1,3-fucose sugar residues, which are considered to be immunogenic in mammals. This altered N-glycosylation when compared to mammalian cells may reduce the potential of maize as a production system for heterologous glycoproteins. Here we report the cloning and characterization of the cDNA sequences coding for the maize enzymes beta 1,2-xylosyltransferase (XylT) and core alpha 1,3-fucosyltransferase (FucT). The cloned XylT and FucT cDNAs were shown to encode enzymatically active proteins, which were independently able to convert a mammalian acceptor glycoprotein into an antigen binding anti-plant N-glycan antibodies. The complete sequence of the XylT gene was determined. Evidence for the presence of at least three XylT and FucT gene loci in the maize genome was obtained. The identification of the two enzymes and their genes will allow the targeted downregulation or even elimination of beta 1,2-xylose and core alpha 1,3-fucose addition to recombinant glycoproteins produced in maize. (c) 2006 Elsevier Ltd. All rights reserved.