Uridine diphosphate (UDP)-galactose is relevant in glycolysis. UDP-galactose is the activated form of Gal, a crucial monosaccharide building block for human milk oligosaccharide (HMO).[2] The activated form of galactose (Gal) serves as a donor molecule involved in catalyzing the conversion of UDP-galactose to UDP-glucose. The conversion is a rate-limiting step essential to the pace of UDP-glucose production that determines the completion of glycosylation reactions.[3]
To further explain, UDP-galactose is derived from a galactose molecule which is an epimer of glucose, and via the Leloir pathway, it is used be used as a precursor for the metabolism of glucose into pyruvate.[4] When lactose is hydrolyzed, D-Galactose enters the liver via the bloodstream. There, galactokinase phosphorylates it to galactose-1-phosphate using ATP. This compound then engages in a "ping-pong" reaction with UDP-glucose, catalyzed by uridylyltransferase, yielding glucose-1-phosphate and UDP-galactose. This glucose-1-phosphate feeds into glycolysis, while UDP-galactose undergoes epimerization to regenerate UDP-glucose.[5]
^Hou, J., Tian, S., Yang, L., Zhang, Z., & Liu, Y. (2021). "A systematic review of the Uridine diphosphate-Galactose/Glucose-4-epimerase (UGE) in plants". Plant Growth Regulation. 93 (3): 267–278. doi:10.1007/s10725-020-00686-1.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Garrett, Reginald H.; Grisham, Charles M. (2017). Biochemistry (6th ed.). Boston, MA, USA: Cengage Learning. ISBN978-1-305-57720-6.
^Nelson, David L.; Cox, Michael M.; Nelson, David L. (2013). Lehninger, Albert L. (ed.). Lehninger principles of biochemistry (6th ed.). Basingstoke: Macmillan Higher Education. ISBN978-1-4292-3414-6.