alpha-D-galactose 1-phosphate + UDP-alpha-D-glucose = alpha-D-glucose 1-phosphate + UDP-alpha-D-galactose Binds 1 zinc ion per subunit. Zinc binding seems to play a structural role. Carbohydrate metabolism; galactose metabolism. Belongs to the galactose-1-phosphate uridylyltransferase type 1 family.