Glycobio: Structure & Glycation Flashcards
What are complex carbs
Hetero-oligosaccharides or hetero-polysaccharides
Contain more than one species of monosaccharides
3 major classes of glycoconjugates
Glycoproteins
Proteoglycans
Glycosphingolipids
D-glucose
Open chain Fischer configuration
C4-6 are derived from glyceroaldehyde
Therefore,
The OH group on C5 determines D or L configuration
What groups on what carbons react to make open chain glucose into a ring
OH group on C5 reacts with aldehyde carbonyl group
Forms two intramolecular hemiacetals
—> which then can form either alpha or beta
Alpha and beta glucose isomers are called
Anomers
What form of glucose is involved in protein glycation?
Open chain form
First step in protein glycation
Formation of Schiff base
Aldehyde group of glucose reacts with an amino group of a protein
Also called an aldimine
Reversible
Amadori arrangement
Second step in protein glycation
Since glucose contains an OH group on C2, next to the Schiff base
The SB can undergo a rearrangement to form a stable ketoamine
Irreversible
HbA1C
Glycated hemoglobin (Hb)
What is glycated in HbA1C
The N-terminal valine of the 2 beta chains in HbA
The 2 valines react with 2 residues of 2 open chain glucoses = 2 Schiff bases are formed
—> then rearrangment —> 2 stable ketoamines (Hb1AC)
Alpha vs. beta configuration glucose
Alpha: H (C5) and OH (C1) = same direction
Beta: they are opposite direction
L vs. D configuration of glucose/sugar
D = H (C5) is down in ring projection
L = H is up
**changing this could affect whether if it is alpha or beta as well!!!
Mannose (Man) vs glucose
C2 position
OH group is up
Galactose (Gal) vs glucose
C4 position
OH group is up
N-acetylglucoamine (GlcNAc) vs. glucose
C2 position
NHCOCH2 replaces OH group
