Journal of Bioscience and Bioengineering, Vol.126, No.1, 15-22, 2018
Heterologous expression, purification and characterization of human beta-1,2-N-acetylglucosaminyltransferase II using a silkworm-based Bombyx mori nucleopolyhedrovirus bacmid expression system
beta-1,2-N-Acetylglucosaminyltransferase II (GnTII, EC 2.4.1143) is a Golgi-localized type II transmembrane enzyme that catalyzes the transfer of N-acetylglucosamine to the 6-arm of the trimanosyl core of N-glycans, an essential step in the conversion of oligomannose-type to complex-type N-glycans. Despite its physiological importance, there have been only a few reports on the heterologous expression and structure function relationship of this enzyme. Here, we constructed a silkworm-based Bombyx mori nucleopolyhedrovirus bacmid expression system and expressed human GnTII (hGnTII) lacking the N-terminal cytosolic tail and transmembrane region. The recombinant hGnTII was purified from silkworm larval hemolymph in two steps by using tandem affinity purification tags, with a yield of approximately 120 mu g from 10 mL hemolymph, and exhibited glycosyltransferase activity and strict substrate specificity. The enzyme was found to be N-glycosylated by the enzymatic cleavage of glycans, while hGnTII expressed in insect cells had not been reported to be glycosylated. Although insects typically produce pauci-mannosidic-type glycans, the structure of N-glycans in the recombinant hGnTII was suggested to be of the complex type, and the removal of the glycans did not affect the enzymatic activity. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.