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Trehalose consists of α-glucose molecules that form disaccharides and is a source of energy for organisms like fungi, plants, invertebrates, and bacteria.
What is Trehalose?
Carbohydrates are a sub-class of biomolecules that is categorized depending on the number of saccharide constituents. When 2 monosaccharides are linked by a glycosidic linkage they form a disaccharide i.e., a carbohydrate an example of a disaccharide is trehalose.
It was H. A. L. Wiggers in 1832 who discovered trehalose in ergot of rye. But the name of this disaccharide was given in 1859 by Marcellin Berthelot based on its source trehala, which was extracted from the weevil’s pupal case.
The monosaccharides in trehalose are linked by 1-1 α-glycosidic linkage. It has a white crystalline appearance and it is also known as α-D-glucopyranosyl-(1→1)-α-D-glucopyranoside and has a formula C12H22O11.
In terms of its components i.e., saccharides it is similar to maltose as it is comprised of 2 glucose units. But, maltose differs with respect to the glycosidic bond, it has α-1→4 glycosidic linkages.
Unlike trehalose where this bond occurs between C-1 of either glucose, on maltose the linkage occurs between C-4 and C-1. If the glycosidic linkage between 2 glucose units is β-(1→4), then they form cellobiose whereas if the linkage is α-(1→6) then isomaltose is formed. Unlike trehalose, maltose is a reducing sugar.
The closed ring structure in trehalose is due to the glycosidic bond between glucose units. Due to this, it is resistant to acid hydrolysis as the aldehyde or the ketone ends cannot bond with lysine or arginine of proteins.
This disaccharide is also stable at high temperatures and in acidic conditions. As it is an energy source and also has high retention trait organisms can endure long dry or freezing situations.
The only anomer of trehalose is α,α-trehalose, and is naturally utilized by different organisms as an energy source. These organisms have inherent pathways and enzymes required to produce this disaccharide biosynthetically. One general metabolic pathway requires a trehalose-phosphate synthase enzyme.
From UDP-glucose the glucose unit is transferred to glucose-6-phosphate and the reaction is catalyzed by trehalose-phosphate synthase to produce threlaose-6-phosphate and UDP. Then, trehalose-P phosphatase catalyzes the dephosphorylation of trehaloses-phosphate.
Trehalose via trehalase enzyme is broken down into glucose units that provide energy in organisms like insects for flight. In the case of higher animals including humans, this reaction is catalyzed by α-glucosidase trehalase that is present in the brush border of cells of the intestinal mucosa.
Biological Importance of Trehalose
This natural disaccharide is biosynthesized in organisms like invertebrates, fungi, and plants. In these organisms, it acts as both the source of carbon and energy. It not only provides a fast energy source but also forms a structural entity in the cell walls of certain organisms and acts as an osmoprotectant.
Plants like Selaginella can survive long periods of dehydration, desiccation, oxidative stress, and heat by utilizing trehalose. During the dry spells it shrinks into a brown ball-like shape but on contact with moisture resumes growth. This phenomenon of resurrection is referred to as poikilohydric.
In omnivores and herbivores, sources like mushrooms, shellfish, and starchy food can deliver trehalose. This is broken down by trehalose that attacks the glycosidic linkage.
It can also be produced synthetically for commercial purposes to produce drugs, food, frozen foods, and cosmetics. In frozen foods like ice cream, this is added as an ingredient to decrease the freezing point of food.
It can also be used as an artificial sweetener as it does not cause a spike in glucose levels in the blood. It also promotes the growth of gut microbes like Clostridium difficile so consumption beyond the required amount is not advised.
Certain toxins are also released as a result of trehalose metabolism. Inborn error of metabolism Trehalase deficiency is a rare metabolic condition in the case of humans where the enzyme is not sufficiently produced and as a result, it accumulates.
It can lead to diarrhea and abdominal discomfort when ingesting dietary trehalose. This deficiency can result due to mutation in the TREH gene.