ISOMALT: CHARACTERISTICS, STRUCTURE, FUNCTIONS - BIOLOGY - 2025

The isomalt (6- O -α-D-glucopyranosyl-glucopyranose) is a regiosiómero disaccharide maltose (disaccharide another produced during the enzymatic hydrolysis of starch) usually found in the branch points of polysaccharides such as amylopectin and glycogen.

As its name implies, it is a disaccharide composed of two D-glucopyranose residues and has various functions in mammalian metabolism. Etymologically speaking, the prefix "iso" of the word isomalt refers to "equal" to maltose.

Haworth representation for Isomaltose (Source: NEUROtiker via Wikimedia Commons)

This disaccharide was discovered in the early 1960s and its industrial synthesis was first achieved in 1980. However, it was not approved until 1900 for human consumption.

Also known as isogentobiose, isomalt is a disaccharide considered a non-cariogenic replacement for sucrose in some products formulated for diabetic or prediabetic patients.

During starch digestion, isomalt and many isomalt oligosaccharides are produced by hydrolysis mediated by different types of enzymes, especially α-amylases and α-glucosidases.

This disaccharide is the main constituent of isomaltose oligosaccharides, also known as IMO, which are produced naturally in fermented foods such as soy sauce and sake.

characteristics

Isomaltose is a disaccharide classified within the group of reducing disaccharides, together with lactose, cellobiose and maltose. When subjected to hydrolysis, it produces two glucose molecules from its constituent monosaccharides.

In the brush border cells of the mammalian intestine, isomalt is pre-digested or hydrolyzed by a disaccharidase enzyme associated with the plasma membrane of the same known as sucrase-isomaltase.

This disaccharide is produced industrially from sucrose, by catalytic reduction in the presence of nickel or by heating glucose (which is why it is present in various types of syrups).

Isomalt and Isomaltulose

There is another disaccharide similar to isomaltose known as isomaltulose, but the difference between the two has to do with the disaccharide from which they are derived, since isomalt is an isomer derived from maltose and isomaltulose is derived from sucrose.

Isomaltulose is actually a disaccharide of glucose and fructose that are linked together by an α-1,6-type glycosidic bond (the same type of bond that joins glucose residues in isomalt).

This disaccharide is widely used in the food industry and is obtained artificially from sucrose and by the enzymatic action of a trehalulose synthase, which causes the structural rearrangement between the monosaccharides that constitute it.

Structure

As already mentioned, isomalt is an isomer of maltose, therefore it is composed of two glucose molecules.

Its constituent monosaccharides are linked together through glucosidic bonds of the α-1,6 type, which differentiates it from maltose, whose bond is of the α-1,4 type.

This type of bond significantly increases the flexibility of the molecule and gives it more conformational possibilities than the others.

Due to the presence of an α-1,6 type bond, isomalt in solution is not crystallized as easily as other disaccharides, however, its commercial presentation is in the form of a crystalline powder.

Its general chemical formula is C12H22O11. It has a molecular weight of 342.3 g / mol and is also known as α-D-glucopyranosyl-glucopyranose. Its melting point is between 98 and 160 ° C, being soluble in water and belonging to the group of fermentable sugars.

Features

Although not as easily digestible, isomalt, as a by-product of the enzymatic degradation of starch, is an essential disaccharide for mammalian nutrition.

Its hydrolysis, mediated by an enzyme present in the brush border membrane known as sucrase-isomaltase, is a source of carbon and energy, since glucose can be easily transported to the cytosol and directed towards essential catabolic pathways.

In the mold Aspergillus nidulans, isomalt is one of the most effective inducers in the induction of the synthesis of amylase enzymes, which has important implications in the biology of this microorganism.

Industrial applications

The main source of isomalt is not natural, as it is obtained industrially from syrups rich in maltose thanks to the action of a transglucosidase enzyme.

Another bacterial enzyme used biotechnologically for the production of isomalt is sucrose isomerase.

Isomalt, thus produced, is incorporated into multiple edible preparations as a sweetener, among which jams, chocolates or sweets and some canned foods stand out. In addition, it is used as a preservative in foods such as cereals, cookies and breads.

It is used with a substitute for sucrose for diabetic patients, since it is not as digestible as common sugar and, therefore, does not significantly increase blood glucose levels (it also contributes lower caloric content).

For its edible applications, it must generally be mixed with other sugars, as it does not have the same properties as common sugar (it does not caramelize when heated and cannot be used for baked preparations).

Because its preparations have a brighter and more transparent appearance, isomalt is commonly used for decorative gastronomic purposes.

It also has uses in the pharmaceutical and cosmetic industry. In addition, it is valid for food formulations designed by domesticated or farm animals.

Related diseases

There is a congenital autosomal disease in humans known as sucrase-isomaltase deficiency or CSID (Congenital sucrase-isomaltase deficiency), which is related to defects in the digestion of osmotically active oligosaccharides and disaccharides.

It has been determined that this disease has to do with several simultaneous factors, among which are gene mutations of the enzymes involved in the process, such as sucrase-isomaltase.

The non-digestion of disaccharides such as sucrose and isomalt produces its "intolerance". The pathological condition is characterized by the development of abdominal cramps, diarrhea, vomiting, headaches, hypoglycemia, excessive gas production, etc.

References

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3. Kato, N., Murakoshi, Y., Kato, M., Kobayashi, T., & Tsukagoshi, N. (2002). Isomaltose formed by α-glucosidases triggers amylase induction in Aspergillus nidulans. Current Genetics, 42 (1), 43–50.
4. PubChem. (2005). Retrieved August 6, 2019, from www.pubchem.ncbi.nlm.nih.gov
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