Glycoconjugates

Proteoglycan, glycoprotein, lipopolysaccharide, and glycolipid.

• Proteoglycan: Sugars + protein, sugars dominant.
• Have glycosaminoglycans attached.
• Function as a component of the extracelluar matrix.

• Glycoprotein: Sugars + protein, protein dominant. found on outside of cell, part of cell to cell interaction. Found on outside of cell due to being only a large polar molecule.
• O-linked or N-linked.

• O-linked: amino acids involved are Ser or Thr
• N-linked: amino acid involed is Asn
• O and N are the molecules that link on the reducing end of the sugars.

• Lipopolysaccharides: Sugars + lipids, sugars dominant.
• Function as a component of the outer membrane of gram-negative cells, target of antibodies.
• Membrane lipid with carbohydrate as hydrophobic head group.

• Glycolipids: Sugars +lipids, lipids dominant.
• Function to provide energy and serve as markers for cellular recognition.
• Membrane lipid with carbohydrate as hydrophobic head group.

Glycoconjugate: Non-sugar compound with covalently attached sugars. Types of glycoconjugates include proteoglycan, glycoprotein, lipopolysaccharide, and glycolipids.

Glycosaminoglycans: they are composed of repeating disaccharide units. The sulfur-containing functional group that is common in them is the sulfuryl group, esterified sulfate groups. The GAGs differ in glycosidic bonds and number of sulfuryl groups.

Peptidoglycan: part of bacterial cell wall. Composed of alternating N-acetylglucosamine and N-acetylmuramic acid in (B1à4) linkage.

Proteoglycan aggregates: enormous supramolecular assemblies of many core proteins all bound to a single molecule of hyaluronan. Glycoconjugate, supermolecular complexes. Core protein (aggrecan) + chondroitin sulfate + kerratan sulfate. Its function is to have binding sites for multiple extracellular matrix proteins -> matrix proteins bind to integrins -> cell migration, cell-cell adhesion, and/or signaling.

Lectins: proteins that bind sugars with high specificity and affinity and ‘read’ the sugar code. Involved in cell recognition, cell adhesion, and signaling. Used as tools for labeling and carbohydrate detection.

• >20 different monosaccharides connected via various types of glycosidic bonds à billions of different oligosaccharides possible. Oligosaccharide sequences can be used as unique molecular recognition tags (biological bar code).
• Used as tools for labeling and carbohydrate detection.
• Involved in cell recognition, cell adhesion, and signaling.