5.2D Sugars: GAGs, Glycoproteins

GAGs

glycosaminoglycans; disaccharides of uronic acid + hexosamine

glycosaminoglycan location

extracellular spaces

non-animal GAG alternatives

pectin in plants; biofilms in bacteria

hyaluronic acid

a GAG found in connective tissue; synovial fluid; vitreous humour of eye

heparin

a GAG found in arterial walls which inhibits blood clotting

types of glycoprotein

proteoglycans, peptidoglycans

proteoglycan location

extracellular matrix

peptidoglycan location

bacterial cell wall

proteoglycans are aggregates composed of

proteins and GAGs (glycosaminoglycans)

GAGs are very hydro[ ]

philic, because they are polyanionic

peptidoglycan is composed of

polysaccharides and polypeptides

peptidoglycan polysaccharide

beta-(1-4) linked glucosamine and N-acetylmuranic acid

peptidoglycan polypeptide

an oligopeptide with a mix of L- and D- amino acids

peptidoglycan is linked by

pentaglycine bridges

glycosylation is found in

nearly all secreted and membrane-bound proteins

glycosylation linkage

almost always O- or N- linked to side chains

O-links in glycosylation

hydroxyl on serine or threonine

N-links in glycosylation

amide N on asparagine

protein glycosylation purpose

define protein structure and function; mediate recognition events

a glycosylated protein is

one with a covalently-linked oligosaccharide

ABO blood types are determined by

glycoproteins on cell surface