(glū'kōs ĕ-pim-ĕr'ās), An enzyme that catalyzes the reversible Walden inversion of UDPglucose to UDPgalactose; a deficiency of this enzyme is associated with one type of galactosemia. Synonym(s): UDPgalactose 4-epimerase, uridine diphosphoglucose 4-epimerase