UDP galactose-4'-epimerase, also known as GALE, enables the body to process a simple sugar called galactose, which is present in small amounts in many foods. Galactose is primarily part of a larger sugar called lactose, which is found in all dairy products and many baby formulas. UDP galactose-4'-epimerase catalyzes two distinct but analogous reactions: the epimerization of UDP-glucose to UDP-galactose, and the epimerization of UDP-N-acetylglucosamine to UDP-N-acetylgalactosamine. Defects in GALE causes epimerase-deficiency galactosemia (EDG), also known as galactosemia type 3. Clinical features include early-onset cataracts, liver damage, deafness and mental retardation.