N-glycan structures of human transferrin produced by Lymantria dispar (gypsy moth) cells using the LdMNPV expression system

N</it>-glycan structures of recombinant human serum transferrin (hTf) expressed by Lymantria dispar</it> (gypsy moth) 652Y cells were determined. The gene encoding hTf was incorporated into a Lymantria dispar</it> nucleopolyhedrovirus (LdMNPV) under the control of the polyhedrin</it> promoter. This virus was then used to infect Ld652Y cells, and the recombinant protein was harvested at 120 h postinfection. N</it>-glycans were released from the purified recombinant human serum transferrin and derivatized with 2-aminopyridine; the glycan structures were analyzed by a two-dimensional HPLC and MALDI-TOF MS. Structures of 11 glycans (88.8% of total N</it>-glycans) were elucidated. The glycan analysis revealed that the most abundant glycans were Man<inf>1–3</inf>(±Fucα6)GlcNAc<inf>2</inf> (75.5%) and GlcNAcMan<inf>3</inf>(±Fucα6)GlcNAc<inf>2</inf> (7.4%). There was only ∼6% of high-mannose type glycans identified. Nearly half (49.8%) of the total N</it>-glycans contained α(1,6)-fucosylation on the Asn-linked GlcNAc residue. However α(1,3)-fucosylation on the same GlcNAc, often found in N</it>-glycans produced by other insects and insect cells, was not detected. Inclusion of fetal bovine serum in culture media had little effect on the N</it>-glycan structures of the recombinant human serum transferrin obtained.