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biochemistry block 4 > Proteoglycans And Glycoproteins > Flashcards

Proteoglycans And Glycoproteins Flashcards

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1
Q

Glycoproteins:

  1. Primarily made of __
  2. Exception to 1?
  3. Charge of CHO chains
  4. Structure
  5. Name?
A
  1. Protein
  2. Mucin
  3. MAY be negatively charged
  4. Short chains, branched, no repeating disaccharide units
  5. Oligosaccharides
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2
Q

Proteoglycans:

  1. Primarily made of __
  2. Charge of CHO chains
  3. Structure
  4. Name?
  5. Give an example of an important proteoglycan
A
  1. Carbohydrate
  2. ALWAYS negatively charged
  3. Long chains, unbranched, with repeating disaccharide units
  4. Glycosaminglycans (GAGs)
  5. Hyaluronic acid
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3
Q

The repeating disaccharide unit of GAGs is primarily

A

[acidic sugar - amino sugar]n

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4
Q

GAGs:

Amino sugars can be sulfated on which carbons?

A

C4 / C6

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5
Q
  1. What is the old term for GAGs

2. What is the name of the GAG storage diseases

A
  1. Mucopolysaccharides

2. Mucopolysaccharidoses

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6
Q

What happens when GAGs are near each other, why?

A

They repel each other because they are always negatively charged

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7
Q

Name an important function of GAGs and 3 places in the body where they are found

A

Shock absorption/lubrication; found in synovial fluid, vitreous humor, and umbilical cord

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8
Q
  1. What happens if you compress a GAGs solution?

2. What happens when you release the compression?

A
  1. They lose water and occupies a smaller volume

2. They spring back (reforms the shell of hydration)

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9
Q
  1. How are the 6 major classes of GAGs recognized? (3 things)
  2. All are extracellular except?
A
  1. Monomeric composition, type of glycosidic linkage, and degree/position of sulfation
  2. Heparin
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10
Q

Chondrotin sulfates:

  1. Found in what parts of the body (5)
  2. What do they form
  3. What is unique about them
A
  1. Cartilage, tendon, bones, ligaments and aorta
  2. Form proteoglycan aggregates, often aggregating non-covalently with hyaluronic acid
  3. Most abundant GAG in the body
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11
Q

Keratan sulfates:

  1. What is unique about them
  2. Where in the body are they found (3)
A
  1. Only GAG with a simple sugar in its disaccharide unit (galactose)
  2. CORNEA, cartilage and bone
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12
Q

Dermatan sulfate:

1. Where in the body is it found (3)

A
  1. Skin, blood vessels and heart valves
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13
Q

Heparin:

  1. Where in the body is it located
  2. Serves as __
A
  1. Liver and mast cells (intracellularly)

2. An anticoagulant

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14
Q

Heparan sulfate:

  1. Difference in the disaccharide units compared to heparin?
  2. Where in the body is it found
A
  1. In heparan sulfate, some glucosamines are acetylated and there are fewer sulfate groups
  2. Cell surfaces and basement membranes
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15
Q

Hyaluronic acid:

  1. Where in the body is it found
  2. What is its disaccharide unit?
  3. What is unique about it (3)
A
  1. Joint and ocular fluids
  2. N-acetylglucosamine and glucuronic acid
  3. Only GAG with no sulfate, not covalently attached to protein, and only GAG also found in bacteria
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16
Q

Structure of proteoglycans:

  1. Chains are separated by __
  2. What kind of structure does this give them?
A
  1. Charge repulsion

2. Bottle brush

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17
Q

What enzyme does venom contain

What does this enzyme do?

A

Hyaluronidase

Breaks through basement membrane so venom can enter

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18
Q

Synthesis of acidic sugars:

  1. What is the difference between D-glucuronic acid and L-iduronic acid?
  2. What does GAG synthesis require? What else is this important for?
A
  1. D-glucuronic acid is derived from glucose; L-iduronic acid is its carbon-5 epimer
  2. UDP-glucuronic acid; making indirect bilirubin into direct bilirubin (conjugation)
19
Q

Synthesis of core protein:

  1. Location?
  2. What happens as it moves through the ER
A
  1. Synthesized on and enters the rER

2. It is glycosylated by membrane-bound transferases

20
Q

Synthesis of the carbohydrate chain:

  1. Begins by synthesis of ?
  2. Linkage starts with transfer of __ to __ by which enzyme?
  3. What happens next?
A
  1. Linkage region on the core protein
  2. Xylose to the -OH of a serine or threonine; xylosyltransferase
  3. 2 galactose molecules are added to make the trihexoside linker (protein-xylose-gal-gal), followed by addition of repeating disaccharide (alternating acidic and amino sugars)
21
Q

Addition of sulfate groups:

  1. Sulfation only occurs after __
  2. Sulfate is carried on ?
  3. What catalyzes sulfation at specific sites
A
  1. After the monosaccharide has been incorporated into the growing chain
  2. 3’-phosphoadenosyl-5’-phosphosulfate (PAPS)
  3. Sulfotransferases
22
Q

Chondrodystrophies:

3 autosomal recessive disorders known from different mutations in DTDST gene coding for a ___

A

Sulfate transporter

23
Q

Linkage region is formed from __

Linkage region is required to __

A

Multiple serine residues

To elongate GAGs

24
Q

Mucopolysaccharidoses:

  1. First 2 disorders known called __
  2. All are autosomal __ disorders except for __
A
  1. Gargoylism (distinct facial features)

2. Recessive; hunter syndrome (X-linked)

25
Q

Hurler syndrome:

  1. AKA
  2. Deficiency in what enzyme
  3. Symptoms
  4. What about this syndrome leads to early death?
  5. Treatment
    * 6. Affects degradation of what 2 things?
A
  1. MPS IH
  2. L-iduronidase deficiency
  3. Corneal clouding, coarse facial features, mental retardation
  4. Deposition in coronary arteries
  5. Enzyme replacement/bone marrow graft (before 18 months)
  6. Heparan and dermatan sulfates
26
Q

Hunter syndrome:

  1. AKA
  2. Deficiency in which enzyme?
  3. Symptoms ?
  4. Affects degradation of what 2 things?
A
  1. MPS II
  2. Iduronate sulfatase deficiency
  3. Macrocephaly, hepatosplenomegaly, mild to severe mental retardation, NO corneal clouding
  4. Heparan and dermatan sulfates
27
Q

Glycoproteins:
1. Location in the cell

  1. Function in the cell
A
  1. Membrane proteins, cytoskeletal proteins, receptors, and extracellular proteins
  2. Antibodies, hormones, collagen, enzymes
28
Q

Sugar chains are carriers of ?

A

Biological information

29
Q

How carbohydrates linked to the protein component ?

A

Through either O-glycosidic or N-glycosidic bonds

30
Q
  1. The N-glycosidic linkage is between?

2. The O-glycosidic linkage is to ?

A
  1. Carbohydrate and asparagine

2. To the -OH of serine, threonine, or hydroxylysine

31
Q
  1. What is the carbohydrate that is directly attached to the protein in N-linked glycoproteins?
  2. In O-linked glycoproteins?
A
  1. N-Acetyl D-Glucosamine

2. N-Acetyl D-Galactosamine

32
Q

What must the sequence of asparagine at the site of glycosylation be?

A

Asn-X-Ser (Thr)

33
Q

Biosynthesis of N-linked glycoprotein:

  1. What is the initial oligosaccharide chain?
  2. Where is it synthesized?
  3. Then it is transferred to where? By what enzyme?
  4. Purpose of the 3 glucoses that make up the linkage region (2)
A
  1. Glc3Man9GlcNAc2
  2. Dolichol (lipid carrier)
  3. To an asparagine residue on the protein by oligosaccharyl transferase
  4. To help oligosaccharide transfer from lipid to protein and protein folding
34
Q

What is the precursor for making dolichol?

A

FPP (farynseal pyrophosphate)

35
Q

Biosynthesis of O-linked glycoprotein:

  1. Occurs post-translationally by stepwise addition of __ ;where?
  2. What is not involved
  3. What is the first sugar to be transferred from UDP? Where is it transferred to?
  4. Addition of a galactose and then sialic acid forms?
A
  1. Sugars in the golgi apparatus
  2. No lipid carriers are involved
  3. GalNAc transferred to serine or threonine residues on a protein
  4. The final trisaccharide sequence on a mucin
36
Q

Lectins:

  1. Include __
  2. Function
  3. 2 of these chaperones?
  4. What do they recognize?
A
  1. Chaperone proteins
  2. Assist in protein folding
  3. Calreticulin and calnexin
  4. High-mannose oligosaccharides with a single glucose remaining on their structure
37
Q

Besides protein folding, what is another function of oligosaccharide chains of glycoproteins?

What reduces the stability of these proteins?

A

Increase the solubility of the proteins and their stability in adverse conditions

Removal of the carbohydrate

38
Q
  1. N-linked glycoproteins are frequently present where?
  2. Lectin-cell membrane bound carb interactions provides for
  3. Key factor in what 4 processes
A
  1. At the cell surface
  2. Specific cell recognition
  3. Fertilization, inflammation, development and differentiation
39
Q

HIV gains entry into the immune system cells by attaching to what 2 receptors?

A

CXCR4 and CCR5 receptors on the cell surface

40
Q

The malarial parasite plasmodium vivax binds to __

A

The erythrocyte chemokine receptor known as the Duffy blood group antigen

41
Q
  1. Most of the hydrolytic enzymes present in the lysosomes are what type of glycoproteins?
  2. Enzymes destined for the lysosomes have which type of residue?
  3. What receptor are these structures recognized by?
A
  1. N-linked
  2. A phosphate group attached to the terminal mannose residue
  3. Man-6-P receptor
42
Q

I cell disease:

  1. Deficiency of the enzyme required for ?
  2. Connective tissue cells in patients with I cell disease contain large inclusions of?
    * 3. Clinical presentation
A
  1. Mannose phosphorylation
  2. GAGs and glycolipids
  3. Mental retardation, skeletal deformities, growth retardation, and death by age 5-7
43
Q
  1. Mannose-6-phosphate residues are recognized by specific receptors where?
  2. In absence of these receptors, what happens to the hydrolytic enzymes?
A
  1. In the golgi apparatus

2. They are secreted in the ECM and body fluids instead of being dispatched to the lysosomes

44
Q

What will the urine contain in someone with I cell disease?

A

High concentration of lysosomal enzymes in the urine

biochemistry block 4 (9 decks)

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