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Galactose uses the same transport system. Fructose, on the other hand, crosses the apical membrane of the enterocyte, using GLUT5. It is thought to cross into the blood capillary using one of the other GLUT transporters. Peptide and amino acid uptake. Peptidases in the glycocalyx cleave proteins to amino acids or small peptides.
Galactose (/ ɡ ə ˈ l æ k t oʊ s /, galacto-+ -ose, "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. [2] It is an aldohexose and a C-4 epimer of glucose. [3] A galactose molecule linked with a glucose molecule forms a lactose molecule.
Many adult humans lack the lactase enzyme, which has the same function as β-galactosidase, so they are not able to properly digest dairy products. β-Galactose is used in such dairy products as yogurt, sour cream, and some cheeses which are treated with the enzyme to break down any lactose before human consumption. In recent years, β ...
After separation from glucose, galactose travels to the liver for conversion to glucose. [12] Galactokinase uses one molecule of ATP to phosphorylate galactose. [2] The phosphorylated galactose is then converted to glucose-1-phosphate, and then eventually glucose-6-phosphate, which can be broken down in glycolysis. [2]
Intermediates and enzymes in the Leloir pathway of galactose metabolism [5] In the first step, galactose mutarotase facilitates the conversion of β-D-galactose to α-D-galactose since this is the active form in the pathway. Next, α-D-galactose is phosphorylated by galactokinase to galactose 1-phosphate.
An example is the glucose symporter SGLT1, which co-transports one glucose (or galactose) molecule into the cell for every two sodium ions it imports into the cell. [27] This symporter is located in the small intestines, [28] heart, [29] and brain. [30] It is also located in the S3 segment of the proximal tubule in each nephron in the kidneys. [31]
Galactokinase is an enzyme (phosphotransferase) that facilitates the phosphorylation of α-D-galactose to galactose 1-phosphate at the expense of one molecule of ATP. [1] Galactokinase catalyzes the second step of the Leloir pathway , a metabolic pathway found in most organisms for the catabolism of α-D-galactose to glucose 1-phosphate . [ 2 ]
Galactosyltransferase is a type of glycosyltransferase which catalyzes the transfer of galactose. An example is B-N-acetylglucosaminyl-glycopeptide b-1,4-galactosyltransferase . The biosynthesis of disaccharides, oligosaccharides and polysaccharides involves the action of hundreds of different glycosyltransferases.