Glycosaminoglycans and Glycoproteins

Question 1

What are the three names for GAGs?

Answer 1

glycoasminoglycans
proteoglycans
mucopolysacchrides

Question 2

GAGs are _______, made up of repeating disaccharide units.

Answer 2

heteropolysaccharides

Question 3

GAGs form the body’s what?

Answer 3

ground substance in ECM

Question 4

What are the functions of GAGs?

Answer 4

cell shape maintenance 
adhesion
migration
cell-cell communication
source of growth factors

Question 5

what is an important characteristic of GAGs?

Answer 5

reversible compressibility = resilient

accounts for resilience of synovial fluid and vitreous humor

Question 6

what are GAGs made up of?

Answer 6

amino sugar - D-glucosamine or D-galactosamine

acidic sugar - D-glucuronic acid or C-5 epimer: L-iduronic acid

Question 7

what is the exception of keratin sulfate?

Answer 7

galactose is present instead of acid sugar

Question 8

what is the bonding of GAGs?

Answer 8

acidic sugar 6C carboxylic acid

N-acetylated amino sugar - 2C amine group

Question 9

what are the 6 major types of GAGs?

Answer 9

hyaluron
chondroitin sulfate
keratan sulfate
dermatin sulfate
heparin
heparan sulfate

Question 10

Hyaluronic acid:

What is it made of?

Answer 10

D-glucuronic acid

N-Acetyl-D-Glucosamine

Question 11

Hyaluronic acid:

Special characteristics

Answer 11

only GAGs not sulfated

only GAG not found covalently attached to protein core in proteoglycans

Question 11

Chondroitin sulfate:

where is it found?

Answer 11

cartilage
bone
heart valves
MOST ABUNDANT GAG!

Question 12

Keratan sulfate:

What is it made of?

Answer 12

D-Galactose

N-Acetyl-D-glucosamine

Question 12

Keratan sulfate:

Where is it found?

Answer 12

cornea
bone
cartilage
aggregated with chondroitin sulfates

Question 13

Deramtan sulfate:

Where is it found?

Answer 13

skin
blood vessels
heart valves

Question 14

heparin:

What is it?

Answer 14

components of intracellular granules of mast cells lining the arteries of lungs, liver and skin

more sulfated than heparan sulfates

the only intracellular GAG
natural anticoagulant
Slows down coagulation
highly sulfated

Question 15

heparan sulfate:

what is it? where is it found?

Answer 15

basement membranes
components of cell surfaces
contains higher acetylated glucosamine than heparin

Question 15

All GAGs (except for hyaluronic acid) are attached to what?

Answer 15

to a protein core = proteoglycan monomers
structure resembles a “bottle brush”

act as a scaffold of which you can attach other GAGs to form larger proteoglycan aggregates

Question 16

each chain contains…?

Answer 16

more than 100 monosaccharides

Question 16

what is proteoglycan in cartilage made of?

Answer 16

chondroitin sulfate and keratan sulfate attached to a protein core

Question 17

how are carbohydrates and proteins linked?

Answer 17

through a trihexoside (Gal-Gal-Xylose) and a Ser residue

Question 17

how do hyaluronic acid associate to proteoglycan monomers?

Answer 17

link proteins - non covalent

Question 18

where is protein synthesized?

Answer 18

ER

Question 19

where is sugar added? How?

Answer 19

Golgi - by glycosyl transferases

Question 20

what are the steps of GAG synthesis?

Answer 20

syn. of amino sugars syn. of acidic sugars syn. of core protein syn. of carbohydrate chain addition of sulfate groups

Question 21

how are sulfate groups added?

Answer 21

PAPs - phosphoadenosinesphosphosulfate | donates sulfate to sugars by sulfotransferase

Question 22

what is heparin?

Answer 22

the only intracellular GAG natural anticoagulant Slows down coagulation highly sulfated

Question 23

what does heparin induce?

Answer 23

the release of cell surface associated TFPI, anti-thrombin III

Question 24

What is warfarin?

Answer 24

used as anticoagulant synthetic analog of Vitamin K SLOWER than heparin

Question 25

Structure of GAGs - percentage?

Answer 25

90% sugar | 10% protein

Question 26

What is UDP used for?

Answer 26

activation of sugars - not incorporated

Question 27

structure of glycoproteins - percentages?

Answer 27

90% proteins | 10% sugars

Question 28

what are the function of membrane-bound glycoproteins?

Answer 28

cell-surface recognition (receptors) cell surface antigenicity contribute to glycocalyx and cell protection

Question 29

what are the functions of extracellular matrix of glycoproteins?

Answer 29

function as protective biological lubricants

Question 30

many intracellular enzymes are what?

Answer 30

glycoproteins - lysosomal enzymes

Question 31

what are mucins?

Answer 31

large glycoproteins negatively charged sialic acid, N-acetyl neuraminic acid (NANA) occupy a large space trap water and serves as protective barriers

Question 32

what is oligosaccharide a mix of?

Answer 32

D-hexoses NANA L-fucose (6-deoxy-L-galactose) C6 has a methyl group

Question 33

how are oligosaccharides attached to proteins?

Answer 33

N-glycosidic link - amino group of Asparagine | O-glycosidic link - OH group of Ser or Thr

Question 34

how is glycophorin linked?

Answer 34

O-linked to hydroxyl group in Ser and Thr by N-acetylgalactosamine

Question 35

what are the two classes of N-linked oligosaccharides?

Answer 35

complex oligosaccharides - N-acetylglucoamine (GlcNAc), L-fucose (Fuc), NANA High mannose oligosaccharides - mannose (Man)

Question 36

what do all N-linked oligosaccharides contain?

Answer 36

3 mannose 2 GlcNAc branched linked to amide nitrogen of Asparagine

Question 37

what is rich in NANA?

Answer 37

mucins

Question 38

what can NANA be in the form of?

Answer 38

CMP form

Question 39

what are the three pathways of glycoprotein sorting?

Answer 39

membrane proteins secreted proteins lysosomal proteins

Question 40

what does the synthesis of N-linked glycosides use?

Answer 40

dolichol and dolichol phosphate