GAGs and Glycoproteins

Question 1

General Structure of Proteoglycans

Answer 1

heteropolysacchrides

Core proteinn with one or more covalently attached GAG to a Ser residue.

GAGs are repeat disaccharides of amino and acid sugars.

Question 2

Functions of GAGs

Answer 2

Cell shape maintenance, Adhesion, Migration, Cell-Cell communication, source of growth factors.

Question 3

Amino sugars in GAGs

Answer 3

D-glucosamine or D-galactosamine

Question 4

Acidic Sugars in GAGs

Answer 4

D-glucuronic acid or C-5 epimer: Liduronic

acid

Question 5

Hyaluron

Answer 5

Found in synovial fluid; vitreous humour; ECM of loose connective tissue;

Large polymers; shockabsorbing

Only GAG not containing sulfate; only GAG not
found covalently attached to proteins in proteoglycans

Question 6

Chondroitin Sulfate

Answer 6

Found in Bone, Heart Vales.

Most abundant GAG

Question 7

Keratan Sulfate

Answer 7

Found in Cornea, Bone, Cartilage

Aggregated with chondroitin sulfate.

Question 8

Dermatan Sulfate

Answer 8

Found in skin, blood vessles, and heart valves.

Question 9

Heparin Sulfate

Answer 9

Component of intracellular granules of mast
cells lining the arteries of lungs; liver and skin

More sulfated than heparan sulfates.

Has a natural anticoagulation property

Question 10

Heparan Sulfate

Answer 10

Basement membranes; components of cell surfaces

Contains higher acetylated glucosamine than
heparin

Question 11

Cartilage proteoglycan structure

Answer 11

Chondroitin Sulfate and Keratan Sulfate attached to a protein core via Ser residues

GAGs linked to hyaluronic acid via a linking protein

Question 12

GalNAc

Answer 12

N-acetylgalactosamine

Question 13

trihexoside in GAG link to Ser

Answer 13

Gal-Gal-Xyl

Question 14

PAPS

Answer 14

phosphoadenosine- phosphosulfate

Sulfate donor in GAG synthesis

Question 15

Sulfotransferase

Answer 15

Transfers sulfate group from PAPS to GAG

Question 16

Steps in proteoglycan synthesis

Answer 16

• synthesis of amino sugars
• synthesis of acidic sugars
• synthesis of core protein
• synthesis of carbohydrate chain (sugars must be in UDP form for assembly similar to glycogen synthesis)
• addition of sulfate groups

Question 17

Heparin and Warfarin

Answer 17

Heparin induces the release of endothelial cell TFPI (tissue factor pathway inhibitor) that is part of the bodies anti-clotting mechanism.

Warfarin is a synthetic analog of vitamin K and has a slower anticoagulation effect compared to heparin

Question 18

General Overview and functions/types of glycoproteins

Answer 18

Proteins attached to oligosaccharides (90% proteins, 10% sugars)

Oligosaccharides are attached via N or O glycosidic linkages of Asn or Ser/Thr

Cell surface receptors
Blood group determinants
Found in collagen and fibronectin
Protective Barrier in cells.

Question 19

Blood Types

Answer 19

Type A Blood contains a terminal GalNAc

Type B Blood contains a terminal Gal

Type AB blood contains both

Type O is missing the terminal glycoprotein

Question 20

Mucins

Answer 20

Large glycoproteins with negatively charged sialic acid, N-acetylneuraminic acid (NANA)

Functions to trap water and as protective barriers.

Question 21

Core N-linked oligosaccharides in mammalian glycoprotein serum

Answer 21

GlcNAc - GlcNAc - Man - (Man, Man) [Y branched Man residues attache to a Man residue]

Question 22

Synthesis of O-linked glycosides

Answer 22

Protein synthesized in rER then extruded in the ER lumen

Glycosylation in the golgi through sequential addition of sugars via glycosyltransferase

Glycosylation begins with N-acetylgalactosamine in UDP form onto Ser or Thr OH group.

glycoproteins then move through golgi for packaging

Question 23

Synthesis of N-linked glycosides

Answer 23

1. Protein Synthesized in rER and enters lumen
2. Branched oligosaccharide synthesized on dolichol
3. oligosaccharide is transferred from the dolichol to Asn residue on the protein
4. trimming of the carb chain as is moves through the rER
5. further trimming &/or addition of monosaccharides in the golgi

Question 24

protein-oligosaccharide transferase

Answer 24

Moves the oligosaccharide from the dolichol to the Asn residue of the protein

Question 25

Degradation of GAGs and glycoproteins

Answer 25

Occurs in lysomomes following endocytosis following phosphorylation of mannosyl residues (N-linked).

mannose 6 phosphate receptors in golgi target enzymes for translocation to lysosomes