Glycosidic bonds are a type of covalent bonds that join carbohydrates (especially glucose) to other molecules (which can be carbohydrates too). They are the bonds found in di-, oligo- and poly-saccharides. They usually involve their alcohol (OH) groups forming ether linkages.
These ether-based glycosidic bonds can be either labelled α or β, based on whether or not the stereochemistry of the two opposite carbons (i.e., the two carbons that are in the ether glycosidic bond in question) are congruent. α glycosidic bonds have the same stereochemistry for each of these two carbons, β glycosidic bonds have opposite stereochemistry on either side.
They are also labelled (in brackets after the α/β) according to the position in which they occur on both of the two molecules (on either side of the bond). α(1→4)[note 1] glycosidic bonds are common in starch and glycogen. α(1→6) glycosidic bonds are less frequent in these polysaccharides but still present, they are the sites at which enzymes like glycogen phosphorylase act, to convert these polymers into their base monomers.
- ↑ Carbon 1 in 1st glucose in link, carbon 4 in 2nd glucose in link