Flashcards in Glycosaminoglycans And Glycoproteins Deck (39):
Basic Description of GAGs
Heteropolysaccharides made up of repeating disaccharide units
relationship between glycosaminoglycan structure and function
The strong negative charges (-Coo- and -Oso3-) cause the molecule to fan outwards and repel adjacent molecules
GAG water binding
The negative charges allow the molecule to bind water, leading to each molecule being surrounded by a hydrated shell that gives them compressibility and the ability to spring back to their original shape (resilience).
What accounts for the resilience of synovial fluid and vitreous humor?
Reversible compressibility of the water shell around GAG molecules
What is the repeating subunit that makes up all GAGs?
Acidic sugar-amino sugar
What are the possible amino sugars in GAGs?
D-glucosamine and D-galactosamine
What are the acidic sugars that make up GAGs?
D-glucuronic acid or the C-5 epimer L-iduronic acid
What is the exception to the acidic sugar rule?
Keratin sulfate where galactose is present instead of an acid sugar
Found in the synovial fluid, vitreous humor, and ECM of loose connective tissue. Large polymers are shock absorbing. Only GAG that doesn't contain sulfate and only GAG that doesn't covalent lay attach to proteins in proteoglycans
found in the cartilage,bone, heart valves. Most abundant GAG.
Found frequently with other GAGs. Found in the cornea, bone, and cartilage with chondroitin sulfates
Skin, blood vessels, and heart valves
Only intracellular GAG. Component of intracellular granules of mast cells lining the arteries of the lungs, liver, and skin. More Sulfates than heparan
Makes up basement membranes, components of cell surfaces. More acetylated glucosamine than heparin
What is hylauronic acid attached to?
Just a sugar, not a protein like all other GAGs
The proteoglycan in cartilage is made up of...
Chondroitin sulfate and keratin sulfate attached to a protein core
What links carbohydrates and proteins in proteoglycans?
A serine attaches a linking sugar of Gal-Gal-Xyl (tri-hexoside) to the protein core
Where are GAGs synthesized?
In the ER and then modified in the Golgi (where acid/amino sugar glycosylation occurs)
Enzymes that catalyze the elongation of polysaccharide chains by alternate placement of their UDP derivatives
Addition of sulfate groups to the proteoglycan:
PAPS donates a sulfate(in the Golgi). Requires sulfotransferase.
role of heparin
Prevents coagulation of blood (inhibits blood clotting)
Tissue Factor Pathway Inhibitor
TFPI (anti-thrombin III). Mainly supplied by endothelial cells. It is an inhibitor that comes into action when limited quantities of factor Xa are generated. TFPI binds to factor Xa and then to tissue factor VIIa forming an inactive quaternary complex. Heparin induces the release of TFPI.
Anticoagulant. Synthetic analog of VitK. Acts slower than heparin so it is administered after
What are the major roles of glycoproteins?
Cell surface receptors. (G-proteins), blood type determinant, in collagen, and serve as a protective barrier, and make up intracellular/lysosomal enzymes.
What is a glycoprotein?
Protein with attached oligosaccharide.
What do extracellular matrix glycoproteins do?
Act as protective biological lubricants
What determines the blood type?
Combination of sugars on the glycoproteins
Large glycoproteins with negatively charged sialic acid, NANA.They occupy a large space and trap water,serving as a protective barrier.
Oligosaccharide attached to the OH group on Serine or Threonine
Oligosaccharide attached to the amide group of asparagine
What links the oligosaccharides to the hydroxyl groups?
What are the two types of N-linked oligosaccharides?
Complex (diverse group of additional sugars) and high mannose (primarily mannose)
What is the charge of an oligosaccharide when NANa is present?
Synthesis of O-linked glycosides
Protein is synthesized in rER and then extruded into lumen of ER. Glycosylation occurs in the Golgi through specific glycosyltransferases that add sugars sequentially.
Degradation of GAGs
GAGs, glycoproteins, and glycolipids occurs in lysosomes following their endocytosis
Inability to degrade with GAGs or glycoproteins
Inability to degrade sphingolipids
Rare syndrome in which hydrolytic enzymes normal found in lysosomes are absent, lack the ability to phosphorylase mannose residues. Usually caused by an issue with protein targeting.