BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Alanine, serine and threonine are also significantly increased. The high serine and threonine content of O-glycosylated regions is due to the presence of clusters of several closely spaced glycosylated hydroxy amino acids in many O-glycosylated proteins.

Detailed explanation-2: -O-glycosylation Glycosylation can occur on amino acids with functional hydroxyl groups, which are most often Ser and Thr. In humans, the most common sugars linked to Ser or Thr are GlcNAc and N-acetylgalactosamine (GalNAc)7 (Fig. 1).

Detailed explanation-3: -Glycosyl residues, mainly N-acetylgalactosamine, mannose, galactose or glucose, can be linked to proteins via asparagine (N-glycosylation) or via hydroxylated amino acids including serine, threonine, and, more rarely, tyrosine, hydroxyproline and hydroxylysine (O-glycosylation) [2, 3].

Detailed explanation-4: -O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine (Ser) or threonine (Thr) residues in a protein. O-glycosylation is a post-translational modification that occurs after the protein has been synthesised.

Detailed explanation-5: -Most of O-glycans have N-acetylgalactosamine (GalNAc) as a common core. Several glycoproteins, such as mucins (MUCs), immunoglobulins, and caseins are examples of O-glycosylated structures. These glycans are further elongated with other monosaccharides and sulfate groups.