Target type: molecularfunction
Binding to aldohexose galactose (galacto-hexose), a common constituent of many oligo- and polysaccharides. [GOC:jl, ISBN:0198506732]
Galactose binding is a molecular function involving the specific recognition and interaction of a protein or other molecule with the monosaccharide galactose. This interaction plays a crucial role in various biological processes, including:
1. **Carbohydrate metabolism:** Galactose binding proteins are essential for the uptake, transport, and metabolism of galactose, a key component of lactose and other complex carbohydrates. Examples include lactose permease (LacY) in bacteria, which facilitates the transport of lactose across the cell membrane, and galactokinase, which phosphorylates galactose in the first step of its metabolic pathway.
2. **Cell signaling:** Galactose binding can trigger signaling pathways in cells. For instance, galectin-3, a soluble galactose-binding lectin, can bind to glycoproteins on the cell surface and initiate signaling cascades that regulate cell growth, differentiation, and apoptosis.
3. **Immune recognition:** Galactose residues on glycoproteins and glycolipids are recognized by immune cells, such as T cells and natural killer cells. These interactions contribute to the activation and regulation of the immune response.
4. **Bacterial adhesion:** Some bacteria utilize galactose-binding proteins (lectins) to adhere to host cells. For example, the FimH adhesin of uropathogenic Escherichia coli binds to mannose and galactose residues on the surface of bladder epithelial cells, facilitating bacterial colonization and infection.
The molecular basis of galactose binding involves the formation of specific non-covalent interactions between the protein and the sugar molecule. These interactions can include hydrogen bonds, van der Waals forces, and hydrophobic interactions. The shape and chemical properties of the binding site on the protein determine the specificity and affinity of the interaction with galactose. Galactose binding proteins often exhibit a high degree of selectivity for galactose over other sugars, ensuring proper recognition and function in biological processes.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Galactokinase | A galactokinase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P51570] | Homo sapiens (human) |
| Galectin-9 | A galectin-9 that is encoded in the genome of human. [PRO:DNx, UniProtKB:O00182] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| lactose | beta-lactose : The beta-anomer of lactose. lactose : A glycosylglucose disaccharide, found most notably in milk, that consists of D-galactose and D-glucose fragments bonded through a beta-1->4 glycosidic linkage. The glucose fragment can be in either the alpha- or beta-pyranose form, whereas the galactose fragment can only have the beta-pyranose form. Lactose: A disaccharide of GLUCOSE and GALACTOSE in human and cow milk. It is used in pharmacy for tablets, in medicine as a nutrient, and in industry. | lactose | |
| methyl alpha-d-galactopyranoside | methyl alpha-D-galactoside : An alpha-D-galactoside having a methyl substituent at the anomeric position. methyl-galactopyranoside: structure in first source | alpha-D-galactoside; methyl D-galactoside; monosaccharide derivative | |
| methyl beta-galactoside | methyl beta-D-galactoside : A beta-D-galactopyranoside having a methyl substituent at the anomeric position. methyl beta-galactoside: RN given refers to (beta-D)-isomer methyl galactoside : A methyl glycoside in which the H of the OH group on C-1 of galactose is replaced by a methyl group. | beta-D-galactoside; methyl D-galactoside; monosaccharide derivative | |
| thiodigalactoside | thiodigalactoside: RN given refers to beta-D-galactopyranoside (D-Gal)-isomer | ||
| methyl lactoside | beta-D-Gal-(1->4)-beta-D-Glc-OMe : A methyl glycoside comprising methyl beta-D-glucoside having an beta-D-galactosyl residue at the 4-position. | disaccharide derivative; methyl glycoside | |
| n-acetyllactosamine | N-acetyllactosamine : A beta-D-galactopyranosyl-(1->4)-N-acetyl-D-glucosamine having beta-configuration at the reducing end anomeric centre. N-acetyllactosamine: RN given refers to D-isomer | beta-D-Galp-(1->4)-D-GlcpNAc | |
| 2-(1,3-benzoxazol-2-ylamino)-5-spiro[1,6,7,8-tetrahydroquinazoline-4,1'-cyclopentane]one | quinazolines | ||
| galactal | galactal: RN given refers to cpd with unspecified isomeric designation; structure | anhydrohexose; glycal |