UDP-Gal is a nucleotide sugar consisting of the nucleotide uridine 5-diphosphate and a phosphate-bound monosaccharide, alpha-D-galactose. Nucleotide sugars are the activated forms of monosaccharides required for cellular metabolism and biosynthesis reactions. UDP-gal serves as a donor substrate for galactosyltransferases in the biosynthesis of galactose-containing glycans and oligosaccharides.
