2.1 The development history and current situation of O-GlcNAc in
China
O-glycoprotein mainly exists in mucus and immunoglobulin. The
O-glycosylation process of forming O-glycoprotein is carried out in the
Golgi apparatus. The sugar chain is covalently linked to the free OH
group of serine or threonine. Usually, the first connected sugar unit is
N-acetylgalactose, and then the sugar residue is successively
transferred to form an oligosaccharide chain, and there is also a case
where only monosaccharides are connected[17]. Sugar donors are also
nucleoside sugars, such as UDP-galactose. The O-glycosylation site has
no conserved sequence, and the sugar chain has no fixed core structure.
Its composition can be either a monosaccharide or a huge sulfonated
polysaccharide. The glycan formed by O-glycosylation has no sugar group,
and there is one or no branch on the carbon skeleton. Since no specific
glycosylation sequence has been found, the analysis of O-glycosylation
is more complicated than other glycosylation.