BetaDgalactopyranose

Beta-D-galactopyranose, commonly written β-D-galactopyranose, is the beta anomer of D-galactose in its six-membered ring form (pyranose). It is a hexose sugar with the molecular formula C6H12O6 and the D-configuration derived from glyceraldehyde. In the pyranose ring, the anomeric carbon (C1) bears a hydroxyl group that is oriented equatorially in the beta form, whereas in the alpha form it is axial.

Galactose is an epimer of glucose at C4, and beta-D-galactopyranose represents its common cyclic representation in the beta orientation. In aqueous solution, galactose undergoes mutarotation between the open-chain form and cyclic hemiacetals; at equilibrium, the beta-pyranose form is typically the most abundant form.

Beta-D-galactopyranose is a component of several biologically important carbohydrates, most notably lactose, which consists of galactose β1-4 glucose. It is also found as a residue in various glycoproteins and glycolipids across organisms. The presence of galactose residues influences cellular recognition, signaling, and immune processes in many contexts.

Metabolically, galactose is processed via the Leloir pathway. Galactose is phosphorylated to galactose-1-phosphate, then converted to UDP-galactose, which can be epimerized to UDP-glucose for entry into glycolysis as glucose-1-phosphate after further conversion. This pathway links dietary galactose to central carbohydrate metabolism.