carbohydrates 3 - heteropolysaccharides Flashcards
what is a heteropolysaccharide
a mixture of monosaccharide units
what are 3 examples of structural opolysaccharides
peptidoglycans
agarose
glycosaminoglycans
what are peptidoglycans (basic)
bacterial cell walls
what are glycosaminoglycans (basic)
extracellular matrix in animals
what 2 types of things compose petidoglycans (general)
mixture of polysaccharides and peptide-like structures
what 2 things compose petidoglycans (specific)
alternating NAH (GlcNAc, N-acetylglucosamine) and NAM (Mur2Ac) N-acetlmuramic acid
what joins NAG and NAM
beta 1–>4 glycosidic bonds
is peptidoglycan linear or not
linear
is peptidoglycan crosslinked and where and how(by what)
yes, adjacent chains are crosslinked by peptide-based structures
whats in the peptide crosslinks of peptidoglycan
L and D amino acids
where are the peptide cross links joined in peptidoglycan
via the Lys side chain to adjacent pentaglycine groups
is the structure of the peptide-like cross-linking the same in Gram + and -
no
what does lysozyme do
breaks bonds between adjacent monosaccharide units
what enzyme breaks bonds between adjacent monosaccharide units in peptidoglycan
lysozyme
what does penicillin do
inhibits formation of peptide cross-links
what kind of bonds join the NAG NAM carbohydrate to the tetra peptide in peptidoglycan
amide bond
how does the 5 glycine connect to do tetra peptide in peptidoglycan
amide bond from side chain of lysine to the pentaglycine
what is the role of glycosaminoglycans in the extracellular matrix
porous network that supports cells
what does glycosaminoglycan associate with
fibrous proteins like collagen
are glycosaminoglycans part of a conjugated protein structure
yes they can be
what are unbranched heteropolysaccharides
repeating disaccharides in linear chains
what composes unbranched heteropolysaccharides (what specifically)
mixture of uronic acid derivatives and glucosamine/galatosamine derivatives
what happens to lots of glycosaminoglycans (structurally)
become sulfated or carboxylated derivatives
what charge do glycosaminoglycans have and why
more negative because the sulfate and carboxylated derivatives are negative
how does the structure adapt due to the negatively charged molecules present in glycosaminoglycans and how
it adopts a linear extended structure to reduce charge repulsion
what kind of interactions are glycosaminoglycans involved in
intermolecular
what is so special about heparin
it is very negatively charged
what kind of groups cause negative charges on glycosaminoglycans
sulfate or carboxylate
what class of molecule is hyaluronic acid / hyaluronate
glycosaminoglycans
what class of molecule is chondroitin sulfate
glycosaminoglycans
what class of molecule is heparin
glycosaminoglycans
how does heparin prevent blood clotting
binding to a protein via electrostatic interactions
what is the shape of heparin and why
very extended to minimize electrostatic interactions (high charge density)
what makes heparin so negative
sulfate group, carboxyl group
why does heparin adopt a highly extended structure
to minimize charge repulsion between negatively charged groups
what kinds of things can be used to create informational structures (cell recognition, cell surface binding, receptor interactions)
polysaccharides and oligosaccharides as glycoconjugates
what are the roles of glycoconjugates
can be used to create informational structures (cell recognition, cell surface binding, receptor interactions)
what is an example of a peptide structure glycoconjugate
peptidoglycan
what is peptidoglycan (what kind of glycoconjugate)
peptide structure glycoconjugate
what are 2 examples of a protein glycoconjugates
Proteoglycans and glycoproteins
what is an example of a lipid glycoconjugate
glycolipid
whats a glycolipid
lipid glycoconjugate
whats a Proteoglycans
protein glycoconjugates
whats a glycoproteins
protein glycoconjugates
whats the general difference with proteoglycans and glycoproteins (like classification)
all proteoglycans are glycoproteins but not all glycoproteins are proteoglycans
what are in for proteoglycans (what are the components in it)
glycosaminoglycan/ protein glycoconjugate
what is another name for glycosaminoglycan/ protein glycoconjugate
proteoglycan
what is the major component of glycosaminoglycan
the heteropolysaccharide (glycosaminoglycan + uronic acid derivatives)
how are the “core proteins” from the proteoglycan linked to the glycosaminoglycan
covalently via glycosidic bonds to Ser side chains
what are 2 common locations of proteoglycans
extracellular matric or integral membrane structures
where are the carbs usually located in the cell with proteoglycans
extracellular
what is syndecan (1 word, its class)
proteoglycan
what is the role of syndecan
cell binding, receptor and cytoskeletal interactions
how is the core protein of syndecan anchored in the cell membrane
via a single alpha helix
what is attached to syndecan and where
multiple glycosaminoglycans attached on the extracellular (N terminal) side
which is the N terminal side of the syndecan core protein
on the extracellular site
which glycosaminoglycans are attached to syndecan
chondroitin sulfate and heparin sulfate
how is chondroitin sulfate and heparin sulfate connected to syndecan
via glycosidic linkages to serine side chains
is the reducing or non reducing end of the sugar attached to syndecan and why
reducing end (need anomeric carbon to attach to serine)
where is the site of intermolecular/binding interactions in syndecan
the glycosaminoglycans
what is the overall structure of syndecans and why
they are extended owing to negative charges
what is the general structure of the condroitin sulfate that links to the serine (and how does it link)
the glycosaminoglycan core (repearing uronic acid structure) then a trisaccharide linker ending in Xyl binds to the serine
which monosaccharide links to serine in the proteoglycan structure
Xylose
which amino acid does xylose link to in the proteoglycan structure
serine
which monosaccharide often joins glycosamined glycans
xyl
which part of xylose is attached to serine of the core protein
the anomeric carbon
what is the concensus sequence of the attachment site
serine glycine X glycine
x=anything
is sulfanation of heparin constant
no it has variable degrees
what are the NA domains of heparan sulfate
the portions that remain as unmodified disaccharide repeats
what are the portions that remain as unmodified disaccharide repeats
NA domain
what are the NS domains of heparan sulfate
the portions that become heavily derivatized, particularly sulfated
what are the portions that become heavily derivatized, particularly sulfated
NS domains
when do the heparan sulfate domains become modified and how
enzymes modify them after synthesis
what happens to the charge ones the domains of heparan become derivatized
they become more negative
what structure changes when they change the carbohydrate (2 things, kinda weird)
allostery, 3ary structure changes
what is the role of NS domains (what do they do)
bind to different proteins and affect their activity
what mediates NS domain binding
electrostatic/ polar interactions
what are 3 different ways that NS domain interactions occur
- allostery/enhanced binding effects on proteins
- acting as co-receptors for extracellular ligands
- cell surface localization
do you expect + or - groups to interact with NS domains
+ve
what does HS binding do when there are more than 1 protein bound
it increases the interactions between the proteins
what can increased NS sites do to concentration of ligands near the membrane and why
it can increase it because there are more receptor ligand interactions with the NS sites
what can happen to concentration of ligands near the membrane when sulfanation is removed and why
less NS sites so less ligand interactions so lower concentration
how do proteoglycans affect ligand-receptor interactions
they enhance
what is something that HS-ligand-receptor complexes can be associated with
HS=heparin sulfate
endocytosis of receptor complexes
what happens when the HS containing structures are shedded (endocytosis of receptor complexes)
HS=heparin sulfate
bound ligands and HS will be dissociated from cell surface
so the HS-ligand-receptor complex will undergo endocytosis and the other HS chain and ligand portions will shed off the membrane
what happens when lipoprotein lipase binds to heparan-sulfate proteoglycans
increase its concentration/localization near the membrane when the proteoglycan is membrane-bound
what does binding of lipoprotein lipase to heparan-sulfate proteoglycans do to reaction rate and why
increases rate of reaction with increase Vmax (increased concentration of enzyme near membrane)
what are 2 ways that membrane bound proteoglycans can be anchored
by transmembrane protein domains or by lipid domains
what are glypicans
phospholipid anchords to membrane
how can you cleave proteoglycans from membrane
phospholipase
how can you cleave glypicans from membrane
protease
what are glycoproteins
protein/carbohydrate conjugats
are all proteoglycans glycoproteins
yes
are all glycoproteins proteoglycans
no
what portion of the glycoprotein differs from proteoglycans
carbohydrate portion
how does the carbohydrate portion of glycoprotein differs from proteoglycans
smaller (oligosaccharides)
more branched
greater variety of saccharides
are there more disaccharide repeats in glycoproteins or proteoglycans
more in proteogylcans
is glycoproteins or proteoglycans more extended and linear
proteogylcans
is glycoproteins or proteoglycans more complex
glycoproteins
is glycoproteins or proteoglycans more branching
glycoproteins
is glycoproteins or proteoglycans more variablity
glycoproteins
how does the carb attach to the protein in glycoproteins and how (What kind of attachment)
covalently attached via serine threonine or asparagine
what are O-linked glycoproteins
ones where the carb is attached via a serine or threonine
what are N-linked glycoproteins
ones where the carb is attached via a asparagine
what kind of linkages are in O-linked oligosaccharides
glycosidic
what kind of linkages are in N-linked oligosaccharides
N-glycosyl
what are the glycosidic bonds like in O-linked glycoproteins
oligosaccharide linked to the oxygen of a ser or thr
what are the N-glycosyl bonds like in N-linked glycoproteins
oligosaccharide linked to the nitrogen of an asn
what are the N-glycosyl bonds like in N-linked glycoproteins
oligosaccharide linked to the nitrogen of an asn
can you have more than one of the O or N linkages in a single protein
yes (oligosaccharides may constitute up to 70% of the mass)
are N or O linkages more common and straightforwards
N
is there more mannose in mature or unmatured oligosaccharides
in non-mature ones
what does glycosylation of proteins lead to (general)
a change in the chemical nature of proteins
what are 4 changes in chemical nature of proteins that happens when they become glycosylated
polarity
solubility
folding (tertiary structure)
interactions with other proteins
what are 3 interactions with other proteins that may change when proteins become glycosylated
- recognition (sorting, signalling)
- protection from proteolysis
- antigenicity (antibody binding)
which structure does adding oligosaccharides do
changes tertiary
when does N-linked glycolsylation occur
during protein synthesis in rough ER
which side of the ER does carbohydrate attachment occur
on the lumen side
where is initial glycosylation processed durther
ER and golgi
where does the glycosylated product sent to determine final location and glycosylation structure
golgi
what are 3 reasons that oligosaccharides are a rich source of structural variation
- multiple monosaccharides as derivatives
- branched structures
- glycosidic configuration variations
what kind of interactions can oligosaccharides in glycoproteins and glycolipids be used for
recognition structure for intermolecular interactions
what are 4 intermolecular interactions that oligosaccharides in glycoproteins and glycolipids be used for
- protein targeting/sorting
- cell-cell interactions
- signalling
- tissue development
order the hexa-polymers in order of least to most…
- hexapeptide
- oligosaccharide
- hexanucleotide
hexanucleotide (4^6)
hexapeptide(20^6)
oligosaccharide(billions)
what are lectins
proteins that bind to carbohydrates (oligosaccharides) with high specificity
which organisms contain lectins
all of them
what are 4 roles of lectins
- cell-cell recognition
- signalling
- adhesion
- intracellular targeting of newly synthesized proteins
what kind of interactions do lectins do
protein ligand interactions
where do oligosaccharides (or parts of them) interact with lectins
with binding sites
what kind of binding process occurs with lectins
equilibrium binding process (Kd values become relevent)
what are cell surface oligosaccharides expressed as
glycolipids and glycoproteins
how do infectious agents use lectins
to interact specifically with surface oligosaccharides (glycolipids and glycoproteins)
what is the specificity of oligosaccharide expression
tissue and cell type specific
what do selectins do
mediate normal cell-cell interactions
which lectin mediates normal cell-cell interactions
selectins
what mediates intracellular traffic and sorting
lectin/oligosaccharide interactions
what binds to Galectin-2
lactose (Gal(beta1–>4)Glc)
