2. Glycoproteins are proteins having covalently
bound carbohydrate.
This process is known as glycosylation.
The history of glycoproteins goes back to as
early as 1805, when Bostock first characterized
the mucus substance of the animal body as
chemically distinct from what we now
recognize as protein.
3. They are classified into three groups
1. O-Linked oligosaccharides
2. N-linked oligosaccharides
3. Glyco phosphatidyl inositol
4. o Involving the hydroxyl side chain of serine or
threonine and a sugar such as N-
acetylgalactosamine
o Ex: mucins
o Anomeric carbon of
NAG attached to
O of serine or
threonine
5. Involving the amide nitrogen of asparagine
and N-acetylglucosamine
5 times more abundant than
o-linked
Anomeric carbon of NAG
attached to amide nitrogen
of an ASM
6. Glycan binds to serine via phosphodiester
bond
Linked to the carboxyl terminal amino acid of a
protein via a phosphoryl-ethanolamine moiety
joined to an oligosaccharide,which in turn is
linked via glucosamine to phosphatidylinositol
7. Structural molecule. Ex: collagens
Lubricant and protective agent. Ex: mucins
Regulation of enzyme. Ex: alkaline phosphate
Regulation of transport molecule.
Ex: transferin
Affect folding of certain protein.Ex: calnexin
8.
9. Lectin can be used to purify glycoprotein
Immobilized lectins are used in affinity
chromatography to selectively capture
glycoproteins and glycopeptides.
primary lectins used ..........
1.wheat germ (Triticum vulgaris)
2. Concanavalin A
Periodic acid-Schiff stain: Detects glycoproteins as
pink bands after electrophoretic separation.
10. • The glycoproteins were found to be
degraded more rapidly than unfractionated
proteins
• Glycoproteins from liver tend to be slightly
larger and more acidic than average
proteins
• So poly- peptide size and net charge are
known to influence protein half-lives, these
factors undoubtedly contribute to the more
rapid degradation of glycoproteins
