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. In the third step, D-galactose-1-phosphate uridylyltransferase converts galactose 1-phosphate to UDP-galactose using UDP-glucose as the uridine diphosphate source. Finally, UDP-galactose 4-epimerase recycles the UDP-galactose to UDP-glucose for the transferase reaction. Additionally, phosphoglucomutase converts the D-glucose 1-phosphate to D-glucose 6-phosphate.
- Holden HM, Rayment I, Thoden JB (November 2003). "Structure and function of enzymes of the Leloir pathway for galactose metabolism". J. Biol. Chem. 278 (45): 43885–8. PMID 12923184. doi:10.1074/jbc.R300025200.
- Frey PA (March 1996). "The Leloir pathway: a mechanistic imperative for three enzymes to change the stereochemical configuration of a single carbon in galactose". FASEB J. 10 (4): 461–70. PMID 8647345. Retrieved 2011-04-01.
- Garrett, Reginald; Grisham, Charles M. (2010), Biochemistry (4 ed.), Cengage Learning, p. 556, ISBN 978-0-495-10935-8