Involved in the metabolism of galactose. Plays an essential role in the incorporation of galactose into meningococcal lipopolysaccharide surface molecules, which are important for pathogenesis. Catalyzes the conversion of UDP-galactose (UDP-Gal) to UDP-glucose (UDP-Glc) through a mechanism involving the transient reduction of NAD (By similarity). UDP-alpha-D-glucose = UDP-alpha-D-galactose Carbohydrate metabolism; galactose metabolism. Homodimer. Belongs to the NAD(P)-dependent epimerase/dehydratase family.