A monosaccharide, such as galactose, bonds to another monosaccharide through dehydration synthesis, which results in the release of water and the formation of a glycosidic bond. A disaccharide is formed when two monosaccharide units are joined together, but an oligosaccharide is formed when three to ten monosaccharide units are joined together.
Multiple monosaccharides are joined together to form polysaccharides. Galactose unites with another monosaccharide to generate a disaccharide in this case. Lactose, for example, is created when galactose and glucose molecules are combined.
Lactulose, a man-made disaccharide made comprised of galactose and fructose, is another option. A galactan is a polysaccharide made up of repeated galactose units in terms of polymers.
Saccharification is the process of breaking down complex carbohydrates into simpler sugars like glucose and galactose. It entails the process of hydrolysis. This involves an enzymatic action in humans and other higher animals. Lactase, a β-galactosidase enzyme, aids digestion in a diet containing galactose (e.g. lactose in dairy products).
Lactase catalyses the hydrolysis of lactose in the small intestine and breaks the -glycosidic bond, releasing glucose and galactose. In the case of ceramide-rich foods, the lactase β -glycosyleramidase complex releases galactose by breaking the β-glycosidic link in glycolipids. Lactose intolerance is caused by the lack or deficiency of lactase, which prevents lactose from being digested into simpler monosaccharides.
Lactose that is not digested in the small intestine travels to the colon, where it is fermented into lactic acid by gut bacteria. Methane and hydrogen gas are created as a result, causing discomfort, intestinal distention, and flatulence. Water is pulled into the colon by the osmotically active lactic acid, causing diarrhoea.
Lactose can be metabolised by microorganisms such as E. coli, which produces β-galactosidase from its lac operon system.
Galactose is absorbed by intestinal cells (enterocytes) via a sodium-dependent glucose transporter, which is similar to the ATP-driven transport mechanism that absorbs glucose. As a result, during intestinal absorption, glucose competes with galactose. Galactose leaves the intestinal cells and enters the circulation via glucose transporter-mediated transport (Glut-).
A two-phase procedure is used to convert galactose to glucose. The enzyme mutarotase converts β -D-galactose into α-D-galactose in the first phase. -D-galactose is transformed to uridine diphosphate (UDP)-glucose in the final step. The Leloir pathway is frequently used during the last phase.
α-D-galactose is phosphorylated by galactokinase to create galactose 1-phosphate in this route. The uridine monophosphate (UMP) group is then added to galactose 1-phosphate by the enzyme galactose-1-phosphate uridyltransferase, resulting in UDP-galactose.
The enzyme UDP galactose-4′-epimerase then interconverts UDP-galactose to UDP-glucose. The De Ley Duodoroff pathway is an alternative to the Leloir pathway in humans and other species. Galactose that has been transformed to glucose is one method galactose enters the glycolytic pathway. As a result, the entire reaction would be as follows:
Galactose + ATP → Glucose-1-phosphate + ADP + H+
The isomerization of glucose 1-phosphate to glucose 6-phosphate is catalysed by phosphoglucomutase. Galactose metabolism takes place in the liver in humans.
Some glucose molecules are converted to galactose in humans and other mammals so that there is more galactose to mix with glucose to generate lactose. This is especially crucial during the milking process.
Lactose is secreted as milk by the mammary gland, especially during breastfeeding. Note that galactose can also be acquired through dietary sources. Hexoneogenesis is the de novo production of glucose and galactose in the mammary gland.
Galactan is a galactose polymer found in hemicelluloses. Galactose monomers bind together to generate galactans in plants like axlewood ( Anogeissus latifolia) and acacia trees.
Glycosylation is the process of adding a carbohydrate component to proteins and lipids, such as galactose. Galactose is a sugar that is found in a variety of glycolipids and glycoproteins. It could, for example, be a component of cerebroside (a glycolipid comprised of a carbohydrate and a sphingolipid). Glucocerebrosides and galactocerebrosides have glucose and galactose carbohydrate residues, respectively.