D(+)-Galactose BioChemica

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Galactose (technical spelling), Gal for short, also galactose (traditional spelling) or also mucilage sugar, is a naturally occurring chemical compound from the group of monosaccharides (simple sugars). Galactose is found, for example, in most living organisms as a building block of oligo- and polycondensates of carbohydrates in various mucilages, from which the German name is derived. In comparison with sucrose, a 10% D-galactose solution has a sweetening power of 63%. - Properties - Galactose is a hexose and, like all hexoses, has the molecular formula C6H12O6. It is stereoisomeric (more precisely a C4 epimer) to glucose and belongs to the subgroup of aldohexoses. - Galactose, like most natural sugars, has D-configuration; L-galactose has only secondary importance in practice. If "galactose" is mentioned without any further name addition (prefix), D-galactose is always meant. - Each ring form and each stereoisomer is assigned its own CAS number: D-galactose: 59-23-4, 19217-07-3, 10257-28-0; L-galactose, 15572-79-9, 41846-90-6, 39392-65-9 - Behavior in aqueous solution - In aqueous solution, intramolecular ring closure occurs to some extent, resulting in equilibrium between the aldoform and the two ring forms (furanose form and pyranose form): At 20 °C, D-galactose dissolved in water is 32% in the α-pyranose form, 64% in the β-pyranose form, 1% in the α-furanose form, and 3% in the β-furanose form. - Equilibrium composition of galactose in aqueous solution at 20 °C - Specific rotation values - α-D-galactopyranose (= six-ring): [α]20D = +150.7° - β-D-galactopyranose: [α]20°/D = +52.8° - Galactose shows mutarotation. Rotation value of aqueous solution: [α]20°/D = +80.2° - Energy metabolism - Through epimerization, galactose is made available for glycolysis in a multi-step process. The following reaction steps are undergone: Galactokinase (GK, EC 2.7.1.6) is used to phosphorylate galactose (1) to galactose-1-phosphate (2) with ATP consumption. In the next step, the enzyme galactose-1-phosphate uridyltransferase (GALT, EC 2.7.7.12) converts the reactant with the participation of UDP-glucose (3): UDP-galactose (4) and glucose-1-phosphate (5) are formed. This enzyme is defective in galactosemia. Glucose-1-phosphate can be isomerized to glucose-6-phosphate (6), an intermediate of glycolysis, by the enzyme phosphoglucomutase (PGM, EC 5.4.2.2). In addition, glucose-1-phosphate together with UTP (uridine triphosphate) can be regenerated to UDP-glucose by UDP-glucose pyrophosphorylase (EC 2.7.7.9). The enzyme UDP-glucose 4-epimerase (UGE, EC 5.1.3.2) ensures that UDP-glucose can be regenerated from UDP-galactose. It can be used again for the reaction in the second step or glycogen biosynthesis. - Occurrence - Galactose, in addition to being a monosaccharide, also occurs as a building block in di- (e.g., lactose), oligo- (e.g., raffinose), and polysaccharides (e.g., agarose). It is also a component of proteoglycans and glycolipids. Via UDP-galactose, the organism provides sufficient starting material for this purpose even in the case of a galactose-free diet. - In the lactating mammary gland, lactose is made available from UDP-galactose and glucose with the help of lactose synthetase in breast milk as an important energy source for infants. Lactose is cleaved into glucose and galactose in the small intestine by the enzyme lactase and supplied to energy metabolism. - Uses - Galactose is used as a dietary supplement or sugar substitute. - Galactose as "brain sugar" - Galactose serves as an insulin-independent energy source for the brain and thus supports both the ability to concentrate and memory performance. This is particularly relevant in patients with neurodegenerative diseases, as they often show insulin resistance. Studies in rats show the positive effects of galactose for the treatment of cognitive deficits and the potential of galactose in the treatment of neurodegenerative diseases.[9] However, other studies showed the opposite effect, according to which the chronic intake of galactose just accelerates aging and neurodegeneration in mice and rats. One difference between the studies is that in the one with the beneficial effect, galactose was administered orally to the animals, whereas in the one with the detrimental effect, it was injected subcutaneously. - Galactose and Diabetes - Because of galactose's insulin-independent cellular uptake, it has little effect on blood glucose levels. The glycemic index of galactose is 20 (glucose=100). As early as the 1930s, doctors at the Charité hospital in Berlin therefore successfully treated diabetes patients with galactose as a sugar substitute. - Galactose in sports - Galactose is also used in the body for the production of glycoproteins and the detoxification of ammonia. Therefore, galactose is used as a dietary supplement in sports during or after exercise. During exercise, ammonia is continuously formed, which is associated with a decrease in performance. By taking galactose, the toxin is transported out of the cell faster and the muscle remains more efficient and can also recover better. - Disease - A hereditary disease in which affected individuals cannot utilize galactose at all due to an enzyme defect is called galactosemia. It comes on immediately after birth. - Studies show that chronic overdose of D-galactose can increase brain aging in mice through increased inflammation and oxidative stress.

D-Galactose is an aldohexose that occurs naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins. In humans, absorption of galactose from food is mediated by Na/Glucose co-transporters. The monosaccharide is absorbed in the small intestine and catabolised in the liver. Galactose is converted through the Leloir pathway to galactose-1-phosphate, then to glucose-1-phosphate, and glucose-6-phosphate which can enter the glucose metabolism. Mutation of any of the enzymes of the conserved Leloir pathway can result in clinical deficiencies known as galactosemias. Research and applications: D-Galactose serves as substrate in enzyme studies (1, 2). Chronic D-Galactose exposure induces neurodegeneration in mice and Drosophila and has therefore been used as an aging model (3). Galactose might serve as a chaperone of alpha galactosidase and is therfore tested in treatments of the Fabry disease (4). The monosaccharide is used to some extend as a sweetener and dietary supplement. It is also used as an ultrasound contrast agent as the absorption by organs or tissues of the body is rather slow for certain preparations of Galactose.

FAQs

What is D-galactose?

D-galactose, also known as D-(+)-galactose is a simple sugar or monosaccharide, consisting of six carbon atoms with an aldehyde functional group. Like glucose, galactose is an aldohexose with chemical formula C6H12O6, differing only in the position of a hydroxyl group, D-galactose is the C4 epimer of D-glucose. This difference gives galactose other chemical and biochemical properties than glucose. Galactose is one of the monosaccharides, along with glucose, found naturally in the D-form in lactose, cerebrosides, gangliosides and mucoproteins. It also forms part of polysaccharides (gums, pectins, mucilages). It can also be part of glycolipids and glycoproteins of cell membranes, especially neurons. In humans, galactose absorption from food is mediated by Na/glucose cotransporters. The monosaccharide is absorbed in the small intestine and catabolized in the liver. Galactose is converted via the Leloir pathway to galactose-1-phosphate, then to glucose-1-phosphate and glucose-6-phosphate, which can enter the glucose metabolism. Mutation of the enzymes of the conserved Leloir pathway can result in clinical deficiencies known as galactosemias. D-galactose is also known as "brain sugar" as it is a component of glycoproteins (oligosaccharide-protein compounds) found in nervous tissue. Other names for D-galactose are: D-galactopyranose, dextrogalactose, Gal.

What are the applications of galactose?

In the medical and biopharmaceutical industry, galactose has been used in trials studying the treatment and diagnosis of hepatitis C, liver cancer, Wilsons disease, diabetic macular edema and focal segmental glomerulosclerosis, among others. In research, D-galactose serves as a substrate in enzymatic studies. Chronic exposure to D-galactose induces neurodegeneration in mice and Drosophila, so it has been used as a model of aging. Galactose could serve as a chaperone for alpha-galactosidase and has therefore been tested in Fabry disease treatments. It is also used as a contrast agent for ultrasound, since absorption by body organs or tissues is rather slow for certain galactose preparations. In the pharmaceutical industry, D-galactose has a wide spectrum of possibilities for exploitation as a vector for the design of prodrugs. It is also used as an excipient in the manufacture of biological drugs.

What is D(+)-galactose used for?

In the medical and biopharmaceutical industry, galactose has been used in trials studying the treatment and diagnosis of hepatitis C, liver cancer, Wilsons disease, diabetic macular edema and focal segmental glomerulosclerosis, among others. In research, D-galactose serves as a substrate in enzymatic studies. Chronic exposure to D-galactose induces neurodegeneration in mice and Drosophila, so it has been used as a model of aging. Galactose could serve as a chaperone for alpha-galactosidase and has therefore been tested in Fabry disease treatments. It is also used as a contrast agent for ultrasound, since absorption by body organs or tissues is rather slow for certain galactose preparations. In the pharmaceutical industry, D-galactose has a wide spectrum of possibilities for exploitation as a vector for the design of prodrugs. It is also used as an excipient in the manufacture of biological drugs.

Is D-galactose a reducing sugar?

Yes, all monosaccharides such as glucose, fructose and galactose are reducing sugars.

What does it mean that a sugar is reducing?

A reducing sugar is any sugar capable of acting as a reducing agent. In alkaline solution, a reducing sugar can form some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a reaction, the sugar is converted to a carboxylic acid. All monosaccharides are reducing sugars, along with some disaccharides, some oligosaccharides and some polysaccharides. Monosaccharides can be divided into two groups: aldoses, which have an aldehyde group, and ketoses, which have a ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars. The common dietary monosaccharides, galactose, glucose and fructose, are all reducing sugars.

What is the melting point of D-galactose?

The melting point of D-galactose is 168-170 °C.

What is the solubility of D-galactose?

The solubility of D-galactose in water is 650 g/L at 20 °C.

What is the CAS number of D-galactose?

The CAS number of D-galactose is 59-23-4.

Where to buy D-galactose?

You can purchase D-galactose from ITW Reagents through its worldwide network of distributors, or through the online store if you are a registered ITW Reagents customer. If you wish to purchase D-galactose for production processes, please contact us directly. Follow this link to find a distributor in your country https://www.itwreagents.com/rest-of-world/en/distributors-rw.

Literature

(1) Doudoroff, M. (1962) Methods Enzymol. 5, 339-341. D-Galactose dehydrogenase from Pseudomonas saccharophila. (2) Dahms, A.S. & Anderson, R.L. (1972) J. Biol. Chem. 247, 2222-2227. D-Fucose metabolism in a Pseudomonad. (3) Cui, X, Zuo, P, Zhang, Q, Li, X, Hu, Y, Long, J, Packer, L, Liu, J (2006) Journal of neuroscience research 84, 647-654. Constant exposure to D-galactose induces memory loss, neurodegeneration, and oxidative damage in mice; R-alpha-lipoic acid shows protective effects. (4) Okumiya et al. (1995) Biochem Biophys Res Commun. 214,1219-24. Galactose stabilizes various missense mutants of alpha-galactosidase in Fabry disease.