Question

What do we get when we joint two α- glucoses via an α1,4 bond?

Is it alpha maltose or beta maltose?
In other words, if we cleave amylopectin with amylase (α-amylase or β-amylase), which form of maltose is the ultimate result?
I think Maltose, which has an axial anomeric hydroxy group, will be the answer to (1) and (2), because α-glucose has has axial anomeric hydroxy group; am I right? However, I could not identify which form of maltose has axial anomeric hydroxy group

Answer 1

The disaccharide formed by joining two α-glucoses via an α1,4 bond is α-maltose. It is characterized by an axial anomeric hydroxy group and is a reducing sugar due to the free anomeric carbon capable of forming an aldehyde group.

Step-by-step explanation:

When two α-glucoses are linked together through an α1,4 glycosidic bond, the disaccharide formed is known as α-Maltose. The anomeric hydroxy group on the second glucose unit in maltose can indeed be in either α or β configuration.

However, when amylopectin is cleaved by α-amylase or β-amylase, the product is α-maltose, in which the hydroxy group on the anomeric carbon of the second glucose is in the same α orientation as the one from which the glycosidic bond is formed.

This gives α-maltose an axial anomeric hydroxy group which characterizes its structure. Furthermore, this configuration allows α-maltose to be a reducing sugar because of the free anomeric carbon that can form an open-chain aldehyde group.