Use of HDEL‐tagged Trichoderma reeseimannosyl oligosaccharide 1,2‐α‐D‐mannosidase for N‐glycan engineering in Pichia pastoris

Therapeutic glycoprotein production in the widely used expression host Pichia pastorisis hampered by the differences in the protein‐linked carbohydrate biosynthesis between this yeast and the target organisms such as man. A significant step towards the generation of human‐compatible N‐glycans in this organism is the conversion of the yeast‐type high‐mannose glycans to mammalian‐type high‐mannose and/or complex glycans. In this perspective, we have co‐expressed an endoplasmic reticulum‐targeted Trichoderma reesei1,2‐α‐D‐mannosidase with two glycoproteins: influenza virus haemagglutinin and Trypanosoma cruzi trans‐sialidase. Analysis of the N‐glycans of the two purified proteins showed a >85% decrease in the number of α‐1,2‐linked mannose residues. Moreover, the human‐type high‐mannose oligosaccharide Man5GlcNAc2was the major N‐glycan of the glyco‐engineered trans‐sialidase, indicating that N‐glycan engineering can be effectively accomplished in P. pastoris.