Glycosylation Flashcards
hexose example
glucose
pentose exmaple
ribose
aldehyde example
glucose
ketone example
ribose
three sugars that are stereoisomers of the same structure
glucose, galactose and mannose
glycosidic linkage
- formed by what carbon
- requirement for reaction to take place
- formed by the anomeric carbon
- this anomeric carbon must be activated with UDP prior to the linkage being formed
alpha maltose
two glucose moleculse
alpha lactose
galactose and glucose
sucrose
fructose and glucose
amylopectin vs amylose
amylose is a straight chain polysaccharide whereas amylopectin is a branched polysaccharide
glucose vs glycogen
- glucose is a single saccharide
- glycogen is a branched polysaccharide with alpha 1,4 linkages between the straight chain monomers and alpha 1,6 linkages at the branch points
chondroitin
- GAG
- bone, cartilage, cornea formation
keratin sulfate
- GAG
- cornea connective tissue
dermatan sulfate
- GAG
- binds LDL to plasma walls
heparan sulfate
- GAG
- aortic wall, basement membrane
heparin
- GAG
- anticoagulant
hyaluronic acid
- GAG
- cell migration, lubricant
- not covalently attached to a protein
GAG general structure
- long linear polysaccharides
- repeating disaccharide units
- considerable negative charge (including sulfate)
glycolipids
-example
-
- gangliosides
- come from sugar modifications of lipids
glycation
-HbA1c
- non-enzymatic glycosylation of proteins
- formation of HbA1c
- simple chemical reaction of sugar and protein side chains
enzymatic glycosylation (conjugation)
- added to
- requirement
- specificity
- occurs to add sugars to other sugars, proteins, or lipids
- requires prior activation of sugar which is accomplished by formation of sugar nucleotides
- enzymes are specific for each different sugar being added as well as the accepting sugar molecule
where is the sugar of glycoproteins located
-except for O-GlcNac, they are located either in the lumen of the ER, the extracellular side of the plasma membrane , or secreted
O-linked glycoprotein
- largely built on Ser/Thr residues
- built one sugar at a time
N-linked glycoprotein
- built on Asp
- initially added to the protein in a 14 sugar block
- constructed on a dilochol phosphate lipid
- initial transfer to N is usually cotranslational in the ER
similaritry between construction of N and O linked glycoproteins
-they are both processed as the glycoprotein traffics from the Er through the golgi
glycoprotein and polysaccharide breakdown
- occurs in the lysosome with the help of many different types of enzymes
- when these enzymes fail you can get lysosomal storage diseases (mucopolysaccharidoses)
pompe disease
single lysosomal enzyme disease defect
proteoglycans
- made of over 90% sugar
- important structural components
- part of the matrix that makes up tissue structure
- found in cartilage, dentin or predentin
- hydrated so they can provid cushion
- charged so they can bind substances like growth factors and chemokines.cytokines
biological recognition
- often involves glycosylation
- protein recognition of carbohydrate structures usually involves a lectin domain
- deficiency disease 2)
examples of uses of carbs in major bodily functions
- blood type
- infection
- cell contacts
carbohydrate structures underlie the differences in ABO blood type groups, contribute to the ability of viruses (flu) or bacteria (H. pylori) to infect, and mediate cell-cell contacts (leukocyte adhesion
chaperon mediated protein folding
-facilitated by carbohydrate binding in the ER
mannose-6-phosphate
-mediates tafficking of lysosomal enzymes
