Glycoprotiens Flashcards
What are the two ways that carbs are attached to protiens
O linked and N linked glycosylation
What is o linked glycosylation
The carbs are attached to the oh on the side chains of serine or threonine residues
The glycosidic bond forms between the anomeric carbon of the carb and the O of the oh in the side chain
What is N linked glycosylation
The carbs attache to the side chain amine nitrogen (NH2) of Asparagine (N) residues
The glycosidic bond forms between the anomeric carbon of the carb and the Nitrogen of the side chain
How are the bonds between carbs and protiens formed
The reaction is catalyzed by enzymes called glycosyltransferases
Originally the carb is attached to a activated sugar nucleotide (UDP)
The bond it broken and the new bond between the protiens nucleotide and the carb is formed
What are N linked olgigoraccharides
The oligosaccharides acts as a chemical tag on the protiens
There’s high mannose type and complex type
What feature of carb make them good information rich molecules
They vary in the identity and number of monosaccharides joined together
The have different types of linkages (alpha 1 6, beta 1,4)
The have either beta or alpha anomers
They have either o or n linked glycosidic bonds to protiens
How does being glycosylation (adding a carb) change the properties of a protien
It increases the amount of chemical info and functionally of the protiens
50 % of protiens are
Glycosylated
What are the three classes of glycoproteins
Glycoprotien
Proteoglycan
Mucin
What is the class glycoprotien
There more protien than carbs by weight
They have diverse roles in function
What is the class proteoglycan
More carb than protien
Has structural and lubricant roles
What is the class mucin
More carb than protien
Role as lubricants and barriers
What is erythropoietin (EPO)
A glycoprotien
A hormone that stimulate the produciton of red blood cells and is 40% carb
It’s made of 3 N linked (to asn) and 1 o linked (to serine)
Being glycosylated enhances stability and function of the protien
What is special about recombinants EPO
They have diff glycosylation than the ones in naturally in the body
What are proteoglycans function
They are lubricants and have roles as structural components in connective tissues
The adhere cells to the extracellular matrix
The protiens are attached to glycosaminoglycans (which make up 95% by weight)
What is cartilage made of
The Proteoglycan aggrecan and collagen
What are glycosaminoglycans structure and function
They are repeating disaccharide with negatively charged coo- and sulphate (SO3-)
They bind water very well because of the - charge
In proteoglycans
What is aggrecan
A Proteoglycan
Repeating disaccharides of chondrotin and keratin sulphate (which are glycosaminoglycans) that are extending from the protiens polypeptide chain
Each of these protein carb complexes are attached to a strand called hyaluronate
The aggrecan acts as a sponge, when there is pressure it releases water and if less pressure it absorbs water due to the negative charges
What are mucins structure and function
They are components in mucus , ex MUC2
Are made up of VNTRs (variable number of tandem repeats)
They’re 80% of carbs by weight, o linked glycosylation
Act as a lubricant in saliva and as a protective barrier when attached to epithelial cells in the intestine (covered by mucus to protect the cells)
What are lectins
Protiens that recognize and bind to specific carbs by noncovalent interactions
Ex. Selectin
What are selectins
A class of lectin
Recruits immune system cells to bind to the site of an injury
What is hemagglutinin
A type of lectin that promotes interactions between cells
Ex. hemagglutinin is on influenza and help it bind to the surface or tester cell and the virus do endocytosis
The virus then need to leave the cell and when it’s released it’s stil bound to the host cell because of hemagglutinin so the enzyme neuraminadase cleaves the carbs and lets the virus leave
