The key difference between maltose and isomaltose is that the maltose has two glucose units joined to each other via an alpha 1-4 bond whereas the isomaltose has two glucose units joined to each other via an alpha 1-6 bond.
Maltose is a disaccharide. It means that it has two sugar units joined to each other. In the case of maltose and isomaltose, the sugar unit is a glucose molecule. Therefore, these two forms of disaccharides differ from each other according to the chemical bonding between the two glucose units. However, both these sugar forms are reducing sugars.
1. Overview and Key Difference
2. What is Maltose
3. What is Isomaltose
4. Similarities Between Maltose and Isomaltose
5. Side by Side Comparison – Maltose vs Isomaltose in Tabular Form
What is Maltose?
Maltose is a disaccharide having two glucose units joined with each other via an alpha 1-4 linkage. Further, this molecule forms during the break down of starch by beta-amylase; it removes one glucose unit at a time, forming the maltose molecule. Moreover, it is a reducing sugar, unlike other disaccharide molecules. This is mainly because, the ring structure of one of the two glucose molecules can open to present a free aldehyde group, but the other glucose unit cannot open like that because of the nature of the glycosidic bond.
Figure 01: Chemical Structure of Maltose
Glucose is a hexose, meaning; it has six carbon atoms in a pyranose ring. In this, the first carbon atom of one glucose molecules links to the fourth carbon atom of the other glucose molecule to form the 1-4 glycosidic bond. The enzyme, maltase can break down the structure of maltose via the catalysing the hydrolysis of the glycosidic bond. This sugar occurs as a component of malt and also present in highly variable quantities in partially hydrolysed starch products. Ex: maltodextrin, corn syrup, etc.
What is Isomaltose?
Isomaltose is a disaccharide having two glucose sugar units linked to each other via an alpha 1-6 linkage. Therefore, this molecule differs from the maltose molecule due to this linkage (because maltose has alpha 1-4 linkage instead of alpha 1-6 linkage). More precisely, isomaltose is an isomer of maltose. It also is a reducing sugar.
Figure 02: Chemical Structure of Isomaltose
Moreover, this molecule forms when we treat high maltose syrup with the enzyme transglucosidase (TG). It results in a product of the caramelization of glucose.
What are the Similarities Between Maltose and Isomaltose?
- Maltose and Isomaltose are reducing sugars
- Also, both are disaccharides.
- Additionally, both have a sweet taste.
What is the Difference Between Maltose and Isomaltose?
Maltose is a disaccharide that has two glucose units joined with each other via an alpha 1-4 linkage whereas Isomaltose is a disaccharide having two glucose sugar units linked to each other via an alpha 1-6 linkage. Hence, this is the key difference between maltose and isomaltose. Furthermore, in maltose, the first carbon of one glucose unit binds with the fourth carbon of the other sugar unit while the first carbon of one of the glucose units binds with the sixth carbon of the other sugar unit in isomaltose. Therefore, the chemical structure is the major difference between maltose and isomaltose. More importantly, isomaltose is an isomer of maltose.
The below infographic sums up the difference between maltose and isomaltose in tabular form.
Summary – Maltose vs Isomaltose
Isomaltose is an isomer of maltose because both these have a nearly similar chemical structure with a slight difference in linking the two sugar units. Therefore, the key difference between maltose and isomaltose is that maltose has two glucose units joined with each other via an alpha 1-4 bond whereas isomaltose has two glucose units joined with each other via an alpha 1-6 bond.
1. “Maltose.” Wikipedia, Wikimedia Foundation, 28 June 2018. Available here
2. “Isomaltose.” Wikipedia, Wikimedia Foundation, 12 July 2018. Available here
1.”Maltose structure”By Zippanova – Own work, (Public Domain) via Commons Wikimedia
2.”Isomaltose structure”By Su-no-G – Own work by ChemDraw, (Public Domain) via Commons Wikimedia
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