Transfers the UMP unit from UDP-glucose (UDP-Glc) to Gal1P. Can also transfer the UMP unit to GlcNAc1P and GalNAc1P. Involved in the general galactose metabolism, and also involved in the lacto-N-biose I/galacto-N-biose (LNB/GNB) degradation pathway, which is important for host intestinal colonization by bifidobacteria. alpha-D-galactose 1-phosphate + UDP-alpha-D-glucose = alpha-D-glucose 1-phosphate + UDP-alpha-D-galactose Carbohydrate metabolism; galactose metabolism. Belongs to the galactose-1-phosphate uridylyltransferase type 2 family.