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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. [3] It is an aldohexose and a C-4 epimer of glucose. [4] A galactose molecule linked with a glucose molecule forms a lactose molecule.
GalT encodes for the protein galactosyltransferase which catalyzes the transfer of a galactose sugar to an acceptor, forming a glycosidic bond. [5] GalK encodes for a kinase that phosphorylates α-D-galactose to galactose 1-phosphate. [6] Lastly, galM catalyzes the conversion of β-D-galactose to α-D-galactose as the first step in galactose ...
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 of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. [1] An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO. [2] Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. [3]
Structure of ceramide, galactosylceramide and glucosylceramide. Galactose or glucose sugars can be attached to a hydroxyl group of ceramide lipids in a different form of O-glycosylation, as it does not occur on proteins. [6] This forms glycosphingolipids, which are important for the localisation of receptors in membranes. [8]
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 ]
GalP is a monosaccharide transporter that uses a chemiosmotic mechanism to transport its substrates into the cytoplasm of E. coli (1). Glucose, galactose and other hexoses are transported by GalP by the use of the proton gradient produced by the electron transport chain and reversible ATPase (1).
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]