Acknowledgements
We thank Professor Sigvard Olofsson for a critical review of the article, and Miya Kudo Høffding for the help with illustration.

Funding
The Danish Research Councils (1331-00133B); a program of excellence 2016 (Copenhagen as the next leader in precise genetic engineering CDO2016: 2016CDO04210) from the University of Copenhagen; The Danish National Research Foundation (DNRF107); Carl Emil Friis og hustru Olga Doris Friis Foundation; The Lundbeck Foundation (R219-2016-545), A.P. Møller og Hustru Chastine Mc-Kinney Møllers Fond til Almene Formaal, Kirsten og Freddy Johansen Fonden, Mizutani Foundation and The Novo Nordisk Foundation. The funders had no role in preparation of the article.

Conflict of interest statement
None declared. Abbreviations
GlcNAc, N acetylglucosamine
MALDI-MS matrix-assisted laser desorption/ionization mass spectrometry
PNA  peanut agglutinin
VVA Vicia villosa lectin (VVA)