in this ppt i described different type of glycoprotein and some methods to synthesize them an their functions in our body

1. Glycoproteins
(N & O glycosylation)

2. • Objectives
• Glycoproteins
• Biological role of glycoproteins
• Glycosylation
• Disease

3. Glycoproteins
• They are proteins that contain oligosaccharide
(glycan) chains covalently attached to their
polypeptide backbones.
• Eight sugars predominate in human
glycoproteins
• Glucose, Galactose, Mannose, N-Acetyl
neuraminic acid, Fucose, N-Acetylgalactosamine,
N-Acetylglucosamine, Xylose .

4. Functions Served by Glycoproteins

5.  Classes of Glycoproteins:
 O-Linked
Glycoproteins
GalNAcSer(Thr)
linkage
GlcNAc-Ser[Thr]
linkage
 N-Linked
Glycoproteins
Amide nitrogen of asparagine and Nacetylglucosamine (GlcNAcAsn)
 GPI-Linked
Glycoproteins

6.  O-glycosidic linkage-hydroxyl side chain of serine or threonine and a
sugar such as Nacetylgalactosamine (GalNAc-Ser[Thr])
 N-glycosidic linkage-amide nitrogen of asparagine and Nacetylglucosamine
(GlcNAcAsn)
 Glycosylphosphatidylinositol-anchored
(GPI-anchored, or GPI-linked)- carboxyl terminal amino acid of a
protein via a phosphoryl-ethanolamine moiety joined to an oligosaccharide
(glycan), which in turn is linked via glucosamine to phosphatidylinosito

7. O-linkage
(N -acetylgalactosamine to serine)

8.  N-linkage
(N -acetylglucosamine to asparagine

9. DIFFERENCES BETWEEN O- & N- LINKED
GLYCOPROTEINS:

N-Linked Glycoproteins
Synthesis:-
• Cotranslationally
• En-bloc transfer of
Oligosachharide chain on
the protein and further
modification.
• Enzymes not membrane
bound.
• Dolichol P-POligosaccharide involved.
• Inhibited by Tunicamycin
 O-Linked Glycoproteins
Synthesis:-
• Post- translationally
• Oligosaccharide chain
synthesized on the protein.
• Enzymes membrane bound.
• Dolichol not involved.
• Not inhibited by Tunicamycin

10. SOME DISEASES DUE TO GLYCOPROTEINS:
Disease
HEMPAS
Leukocyte adhesion deficiency, type II
Paroxysmal nocturnal hemoglobinuria
I-cell disease
Congenital disorders of glycosylation

11.  HEMPAS:
 Hereditary Erythroblastic Multinuclearity With A Positive Acidified
Lysis Test .
 Also known as Congenital Dyserythropoietic Anemia Type II.
 Claimed to be due to defects in alpha–mannosidase II
 Characterized by
– Ineffective erythropoiesis
– Hemolysis & erythroblast morphological abnormalities
– Hypoglycosylation of some red blood cell (RBC) membrane proteins.
 Treatment consists of frequent blood transfusions and chelation
therapy

12.  Leukocyte adhesion deficiency (LAD)
 A congenital disorder of glycosylation
 Mutations affecting the activity of a Golgi-located GDP-fuc
transporter
 Marked decrease in neutrophil rolling
 Subjects suffer
– Life-threatening, recurrent bacterial infections
– Psychomotor and mental retardation
 The condition appears to respond to oral fucose

13.  Paroxysmal Nocturnal Hemoglobinuria:

14. I-CellDisease:

15.  Congenital Disorder of Glycosylation
Previously called carbohydrate-deficient glycoprotein
syndrome.
 Glycosylation of a variety of tissue proteins and/or lipids is
deficient or defective.
 CDG-I mainly in ER & related to steps prior processing of
glycan chains and transfer of oligosac chain to protein.
 CDG-II includes all defects localized in the processing of Nglycans on the
glycosylated protein. These are situated mainly
in the Golgi compartment.
 Often cause serious, sometimes fatal, malfunction of several
different organ systems (especially the nervous system,
muscles, and intestines) in affected infants