Trehalose (from Turkish tıgala – a sugar derived from insect cocoons + -ose)[3] is a
sugar consisting of two molecules of
glucose. It is also known as mycose or tremalose. Some bacteria, fungi, plants and invertebrate animals synthesize it as a source of energy, and to survive freezing and lack of water.
Extracting trehalose was once a difficult and costly process, but around 2000, the Hayashibara company (
Okayama, Japan) discovered an inexpensive extraction technology from starch.[4][5] Trehalose has high water retention capabilities, and is used in food, cosmetics and as a drug. A procedure developed in 2017 using trehalose allows sperm storage at room temperatures.[6]
Structure
Trehalose is a disaccharide formed by a 1,1-glycosidic bond between two α-glucose units. It is found in nature as a
disaccharide and also as a monomer in some polymers.[7] Two other
stereoisomers exist: α,β-trehalose, also called neotrehalose, and β,β-trehalose, also called isotrehalose. Neither of these alternate isomers has been isolated from living organisms, but isotrehalose has been was found in starch hydroisolates.[7]
Synthesis
At least three biological pathways support trehalose
biosynthesis.[7] An industrial process can derive trehalose from
corn starch.[8]
Properties
Chemical
Trehalose is a
nonreducing sugar formed from two glucose units joined by a 1–1 alpha bond, giving it the name α-D-glucopyranosyl-(1→1)-α-D-glucopyranoside. The bonding makes trehalose very resistant to acid
hydrolysis, and therefore is stable in solution at high temperatures, even under acidic conditions. The bonding keeps nonreducing sugars in closed-ring form, such that the
aldehyde or
ketone end groups do not bind to the
lysine or
arginine residues of proteins (a process called
glycation). Trehalose is less soluble than
sucrose, except at high temperatures (>80 °C). Trehalose forms a rhomboid crystal as the dihydrate, and has 90% of the calorific content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the
dihydrate.
Anhydrous forms of trehalose can show interesting physical properties when heat-treated.
Trehalose aqueous solutions show a concentration-dependent clustering tendency. Owing to their ability to form
hydrogen bonds, they self-associate in water to form clusters of various sizes. All-atom molecular dynamics simulations showed that concentrations of 1.5–2.2 molar allow trehalose molecular clusters to
percolate and form large and continuous aggregates.[9]
Trehalose directly interacts with nucleic acids, facilitates melting of double stranded DNA and stabilizes single-stranded nucleic acids.[10]
Biological
Organisms ranging from bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants have enzymes that can make trehalose.[7]
In nature, trehalose can be found in
plants, and
microorganisms. In animals, trehalose is prevalent in shrimp, and also in
insects, including grasshoppers, locusts, butterflies, and bees, in which trehalose serves as blood-sugar.[citation needed]Trehalasegenes are found in
tardigrades, the microscopic
ecdysozoans found worldwide in diverse extreme environments.[11]
Trehalose is the major carbohydrate energy storage molecule used by insects for flight.[citation needed] One possible reason for this is that the
glycosidic linkage of trehalose, when acted upon by an insect trehalase, releases two molecules of glucose, which is required for the rapid energy requirements of flight. This is double the efficiency of glucose release from the storage polymer
starch, for which cleavage of one glycosidic linkage releases only one glucose molecule.[citation needed]
Even within the plant kingdom, Selaginella (sometimes called the resurrection plant), which grows in desert and mountainous areas, may be cracked and dried out, but will turn green again and revive after rain because of the function of trehalose.[12]
The two prevalent theories as to how trehalose works within the organism in the state of
cryptobiosis are the
vitrification theory, a state that prevents ice formation, or the water displacement theory, whereby water is replaced by trehalose.[11][14]
In bacterial cell wall, trehalose has a structural role in adaptive responses to stress such as osmotic differences and extreme temperature.[15] Yeast uses trehalose as a carbon source in response to abiotic stresses.[16] In humans, the only known function of trehalose is as a neuroprotective, which it accomplishes by inducing
autophagy and thereby clearing
protein aggregates.[citation needed]
Trehalose has also been reported for anti-bacterial, anti-biofilm, and anti-inflammatory (in vitro and in vivo) activities, upon its esterification with fatty acids of varying chain lengths.[17]
Nutritional and dietary properties
Trehalose is rapidly broken down into glucose by the
enzymetrehalase, which is present in the
brush border of the
intestinal mucosa of omnivores (including humans) and herbivores.[18]: 135 It causes less of a spike in
blood sugar than glucose.[19] Trehalose has about 45% the sweetness of sucrose at concentrations above 22%, but when the concentration is reduced, its sweetness decreases more quickly than that of sucrose, so that a 2.3% solution tastes 6.5 times less sweet as the equivalent sugar solution.[20]: 444
Deficiency of trehalase
enzyme is unusual in humans, except in the
Greenlandic Inuit, where it is present in only 10–15% of the population.[21]: 197
Metabolism
Five biosynthesis pathways have been reported for trehalose. The most common pathway is TPS/TPP pathway which is used by organisms that synthesize trehalose using the enzyme trehalose-6-phosphate (T6P) synthase (TPS).[22] Second, trehalose synthase (TS) in certain types of bacteria could produce trehalose by using maltose and another disaccharide with two glucose units as substrates.[23] Third, the TreY-TreZ pathway in some bacteria converts starch that contain maltooligosaccharide or glycogen directly into trehalose.[24] Fourth, in primitive bacteria, trehalose glycisyltransferring synthase (TreT) produces trehalose from ADP-glucose and glucose.[25] Fifth, trehalose phosphorylase (TreP) either hydrolyses trehalose into glucose-1-phosphate and glucose or may act reversibly in certain species.[26] Vertebrates do not have the ability to synthesize or store trehalose.[27] Trehalase in humans is found only in specific location such as the intestinal mucosa, renal brush-border, liver and blood. Expression of this enzyme in vertebrates is initially found during the gestation period that is the highest after weaning. Then, the level of trehalase remained constant in the intestine throughout life.[28] Meanwhile, diets consisting of plants and fungi contain trehalose. Moderate amount of trehalose in diet is essential and having low amount of trehalose could result in diarrhea, or other intestinal symptoms.[29]
In 1832, H.A.L. Wiggers discovered trehalose in an
ergot of rye,[36] and in 1859
Marcellin Berthelot isolated it from Trehala manna, a substance made by
weevils and named it trehalose.[37]
Trehalose has long been known as an
autophagy inducer that acts independently of
mTOR.[38] In 2017, research was published showing that trehalose induces autophagy by activating
TFEB,[39] a protein that acts as a master regulator of the autophagy-
lysosome pathway.[40]
^Patrick, Jennifer L.; Elliott, Gloria D.; Comizzoli, Pierre (1 November 2017). "Structural integrity and developmental potential of spermatozoa following microwave-assisted drying in the domestic cat model". Theriogenology. 103: 36–43.
doi:
10.1016/j.theriogenology.2017.07.037.
PMID28772113.
^Sapir L, Harries D (February 2011). "Linking trehalose self-association with binary aqueous solution equation of state". The Journal of Physical Chemistry B. 115 (4): 624–34.
doi:
10.1021/jp109780n.
PMID21186829.
^Bezrukavnikov S, Mashaghi A, van Wijk RJ, Gu C, Yang LJ, Gao YQ, Tans SJ (October 2014). "Trehalose facilitates DNA melting: a single-molecule optical tweezers study". Soft Matter. 10 (37): 7269–77.
Bibcode:
2014SMat...10.7269B.
doi:
10.1039/C4SM01532K.
PMID25096217.
^Sola-Penna M, Meyer-Fernandes JR (December 1998). "Stabilization against thermal inactivation promoted by sugars on enzyme structure and function: why is trehalose more effective than other sugars?". Archives of Biochemistry and Biophysics. 360 (1): 10–4.
doi:
10.1006/abbi.1998.0906.
PMID9826423.
^Tillequin F (July 2009). "Le Tréhala, une drogue à la croisée des chemins" [Trehala, a meeting point between zoology, botany, chemistry, and biochemistry]. Revue d'Histoire de la Pharmacie (in French). 57 (362): 163–72.
doi:
10.3406/pharm.2009.22043.
PMID20027793.
^Menzies FM, Fleming A, Rubinsztein DC (June 2015). "Compromised autophagy and neurodegenerative diseases". Nature Reviews. Neuroscience. 16 (6): 345–57.
doi:
10.1038/nrn3961.
PMID25991442.
S2CID19272817.