Molecular cloning of cDNA encoding N-acetylglucosaminyltransferase II fromArabidopsis thaliana

N-acetylglucosaminyltransferase II (GnTII, EC 2.4.1.143) is a Golgi enzyme involved in the biosynthesis of glycoprotein-bound N-linked oligosaccharide s, catalysing an essential step in the conversion of oligomannose-type to c omplex N-glycans. GnTII activity has been detected in both animals and plan ts. However, while cDNAs encoding the enzyme have already been cloned from several mammalian sources no GnTII homologue has been cloned from plants so far. Here we report the molecular cloning of an Arabidopsis thaliana GnTII cDNA with striking homology to its animal counterparts. The predicted doma in structure of A. thaliana GnTII indicates a type II transmembrane protein topology as it has been established for the mammalian variants of the enzy me. Upon expression of A. thaliana GnTII cDNA in the baculovirus/insect cel l system, a recombinant protein was produced that exhibited GnTII activity.