CH 11 Carbohydrates P2 Flashcards
What protects newborns from infection?
human milk oligosaccharides
How many oligosaccharides are there in human milk?
150 (amount / comp vary per woman)
Oligosaccharides are carbohydrates that help infants in?
protection against bacterial infection
What can oligosaccharides prevent the growth of?
Streptococcus bacteria
Streptococcus bacteria can be transferred to infant via, and cause?
vaginal epithelium
pneumonia, blood poisoning, meningitis
Glycoproteins
when carbs are linked to proteins
mainly protein by weight
membrane proteins
variety of roles
3 Main Classes of Glycoproteins
- Glycoproteins
- Proteoglycans
- Mucins / Mucoproteins
Proteoglycans
attached to polysaccharide glycosaminoglycan (make up 95% of this)
mainly carb by weight
structural role, lubricant.
Mucins / Mucoproteins
characteristically attached by N-acetylgalactosamine.
mainly carb by weight.
Lubricants.
glycoprotein component of mucus.
What link carbohydrates to proteins?
Asparagine (N-linked) or
Serine / Threonine (O-linked) residues
In all glycoproteins carbs are attached to which atoms?
N in side chain asparagine (N-linkage)
O in side chain of serine / threonine (O-linkage)
All N-linked polysaccharides have a common?
pentasaccharide core
A pentasaccharide core consists of?
3 mannoses
2 N-acetylglucosamine units
Glycosidic bonds occur btw?
proteins and carbs
Glycosidic Bond
links carb to side chain of asparagine (N-linked) or side chain of serine / threonine (O-linked)
Erythropoietin
glycoprotein vital hormone 40% carb by weight secreted by kidney into blood stimulates prod of RBC's
Glycosylation of Erythropoietin enhances?
stability of protein in the blood
What are the oligosaccharides linked to in Erythropoietin?
3 asparagine residues
1 serine residue
Glycosylation functions in?
nutrient sensing
N-acetylglucosamine (GlcNAc) attaches to which residues via which enzyme?
serine / threonine
GlcNAc transferase or GlcNAcase
GlcNAc
modifies protein
attached to protein when nutrients are abundant
GlcNAcase
reversible
removes carb
improper reg –> pathological cond’s
Glycosaminoglycans
repeating units of disaccharide 1 derivative of amino sugar 1 carries ( - ) charge as carboxylate / sulfate
Proteoglycans are key components of?
ECM
lubricants
Mucopolysaccharidoses (ex Hurler Disease)
pathological cond’s
result from inability to degrade proteoglycans
Hurler Disease
glycosaminoglycans cannot be degraded
excess stored in soft tissue of facial regions
wide nostrils, depressed nasal bridge, thick lips / earlobes / irregular teeth.
Proteoglycans are important components of?
cartilage
Cartilage
proteoglycan aggrecan and protein collagen
What cushions joints by releasing water on impact and then rebinding water?
glycosaminoglycan component of aggrecan
Proteoglycan structure from cartilage is?
proteoglycan monomers emerge laterally at reg intervals from opp sides of central filament hyaluronate
Chitin
glycosaminoglycan
in insects wings
in insects, crustaceans, arachnids exoskeleton
What is the most abundant carbohydrate in the world?
chitin
The protein component in mucin are?
extensively glycosylated to serine / threonine residues w/ 1st carb N-acetylgalactosamin
Region: VNTR - Variable Number Tandem Repeats
site of glycosylation
highly glycosylated - forces molecule into extended conformation
region of protein backbone rich in serines / threonines.
Functions of Mucins
- lubricants, adhere to epithelial cells - protective barrier.
- overproduced in cond’s - bronchitis, cystic fibrosis, adenocarcinomas (cancer of glandular cells - epithelial origin)
Where is the VNTR located?
mucin btw Cys rich domains
Cys-rich Domain and D domain
in mucin
facilitate polymerization of many molecules
Processed Chitin
carrier - assist in drug delivery (surgical stiches) component of personal care products, additive in food products.
Chitin to Chitosan
water soluble to insoluble.
demineralization.
treat w/ protease to remove proteins.
Depigmentation of Chitin
dissolve carotenoids.
deacylated.
Protein glycosylation takes place where?
lumen of ER.
Golgi complex.
N-linked glycosylation begins in the _____ and continues into the _____.
ER.
Golgi complex.
O-linked glycosylation takes place in the?
Golgi complex
Golgi Complex
sorting center for proteins (various fates)
Dolichol Phosphate
isoprene derivative.
carries lg oligosaccharides - attach to Asp.
Enzymes responsible for oligosaccharide assembly are?
glycosyltransferases
Glycosyltransferases
catalyze formation of glycosidic bonds
Monosaccharide substrates for glycosyltransferases are activated by?
attachment to uridine diphosphate (UDP)
Blood groups are based on?
glycosylation patterns
Human ABO Blood Groups
reflect specificity of glycosyltransferases
All blood groups share?
oligosaccharide foundation: O
A form
created when N-acetylgalactosamine added to O by specific glycosyltransferase
B form
created when galactose added by another transferase
Blood Type: O
lack both enzymes
Blood Type: AB
express both enzymes
Blood Type A or B:
express only one enzyme
one capable of creating that oligosaccharide
I-cell Disease (Mucolipidosis II)
lysosomal enzymes secreted into blood rather than to lysosome
I-cell disease results in?
mutation.
disrupts digestion process in lysosomes.
lysosomes have lg inclusions of undigested glycosaminoglycans and glycolipids.
carb doesn’t direct key enzymes to lysosome, not synthesized properly.
What happens to the digestive enzymes in I-cell Disease?
synthesized.
sent to blood / urine.
Patients w/ I-cell Disease lack the ability to?
phosphorylate mannose to create mannose 6-phosphate
How are oligosaccharides seq’d?
enzymes that cleave specific glycosidic bonds
MALDI-TOF - Oligosaccharides
used to identify released sugars
Lectins
specific carb-binding proteins.
Lectins are a particular class of?
glycan-binding proteins specific to oligosaccharides on cell surface
Lectin Classes
C-type
L-Lectins
C-type Lectins
Ca2+ ion facilitates interaction btw protein and carb
Selectins
member of C-type Lectin.
bind immune-system cells to sites of injury.
inflammatory response.
L-Selectine
member of C-type Lectin.
allow attachment of embryo to uterus.
L-Lectin
chaperones (assist in protein folding).
in eukaryotic ER.
some in potent insectisides.
Influenza Virus
binds to sialic acid residues.
How do many pathogens gain entry into cells?
binding to carbs on cell surface
Influenza Virus Process
- recognizes sialic acid residues linked to galactose residues on cell surface of glycoproteins.
- viral protein hemagglutinin (lectin) binds to sugars.
How does Influenza spread?
when viral protein neuraminidase (sialidase) cleaves glycosidic bonds btw sialic acids residues and rest of cellular glycoprotein.
frees virus to infect new cells.
Neuraminidase Inhibitors
Tamiflu
Relenza
Plasmodium Falciparum
parasitic protozoan.
causes malaria.
relies on glycan binding to infect, colonize host.
𝛂-Glucosidase (Maltase) Inhibitors
help maintain blood glucose homeostasis.
medications exist to inhibit this enzyme.
Hyperglycemia
advanced glycation product.
type 1 diabetes (absent insulin).
type 2 diabetes (ineffective insulin)
Glycogen Digestion and Starch
degradation into smaller oligosaccharides by α-amylase.
further digested by α-glucosidase.
α-amylase
secreted by salivary glands and pancreas
Competitive inhibitors of the enzyme α-glucosidase are?
acarbose and miglitol.
taken at meal start to reduce post-meal glucose absorption in type 2 diabetes.
